Building a Network - Study Notes

Building a Simple Network (ICT) Study Notes

+W - Technology Skills For Women Series1

(Master Copy)

http://SlideShare.net/OxfordCambridge

1 Men are allowed to read too, if they wish, as the language style and the document format are universal.

http://slideshare.net/OxfordCambridge

Study Notes http://SlideShare.net/OxfordCambridge

2 | P a g e B u i l d i n g a S i m p l e N e t w o r k ( I C T )

Contents

About “+W - Technology Skills For Women” series ................................................................................ 5

Sources: ................................................................................................................................................... 6

A. Application sharing through networks .................................................................................................... 8

1. Major components of a computer system .......................................................................................... 8

Question ................................................................................................................................................ 12

Quiz ........................................................................................................................................................ 13

2. Network interface card ...................................................................................................................... 13

Quiz ........................................................................................................................................................ 15

Quiz ........................................................................................................................................................ 16

Summary ................................................................................................................................................ 16

B. Understanding binary basics ................................................................................................................. 17

1. Bits, bytes and measurement terms ................................................................................................. 17

Quiz ........................................................................................................................................................ 20

2. Conversion between decimal and binary .......................................................................................... 21

Quiz ........................................................................................................................................................ 24

Quiz ........................................................................................................................................................ 26

3. Conversion between binary and hexadecimal .................................................................................. 26

Quiz ........................................................................................................................................................ 29

Quiz ........................................................................................................................................................ 31

Summary ................................................................................................................................................ 32

C. Using a PC on a network ........................................................................................................................ 33

1. Basic Networking Terminology .......................................................................................................... 33

2. Network Applications ........................................................................................................................ 34

3. Computer Networks .......................................................................................................................... 36

Summary ................................................................................................................................................ 38

D. Working with PC technology ................................................................................................................. 39

1. Exercise overview .............................................................................................................................. 39

2. Task 1: Identifying PC components ................................................................................................... 39

Step 1 of 1 .................................................................................................................................................. 40

Result ......................................................................................................................................................... 40

3. Task 2: Interpreting numerical systems ............................................................................................ 40

Step 1 of 5 .............................................................................................................................................. 41

Result ..................................................................................................................................................... 41

Step 2 of 5 .............................................................................................................................................. 42

Result ..................................................................................................................................................... 42



Step 3 of 5 .............................................................................................................................................. 42

Result ..................................................................................................................................................... 42

Step 4 of 5 .............................................................................................................................................. 43

Result ..................................................................................................................................................... 43

Step 5 of 5 .............................................................................................................................................. 43

Result ..................................................................................................................................................... 43

E. OSI model layers and functions ............................................................................................................. 44

1. Origins of the OSI reference model ................................................................................................... 44

Quiz ............................................................................................................................................................ 46

Answer ....................................................................................................................................................... 46

2. OSI layers and functions .................................................................................................................... 47

Quiz ............................................................................................................................................................ 53

Answer ....................................................................................................................................................... 53

3. Data communications ........................................................................................................................ 53

Quiz ............................................................................................................................................................ 55

Answer ....................................................................................................................................................... 56

Quiz ............................................................................................................................................................ 60

Answer ....................................................................................................................................................... 60

4. The TCP/IP protocol stack .................................................................................................................. 60

Quiz ............................................................................................................................................................ 62

Answer ....................................................................................................................................................... 62

Summary ................................................................................................................................................ 62

F. Working with the OSI model ................................................................................................................. 64

Exercise overview .................................................................................................................................. 64

Task1: Networking terms and functions................................................................................................ 64

Result ..................................................................................................................................................... 64

Step 2 of 3 .............................................................................................................................................. 65

Result ..................................................................................................................................................... 65

Step 3 of 3 .............................................................................................................................................. 66

Result ..................................................................................................................................................... 66

Task 2: Functions of the OSI model ....................................................................................................... 66

1 of 1 ...................................................................................................................................................... 67

Result ......................................................................................................................................................... 67

Task 3: The data encapsulation process ................................................................................................ 67

Step 1 of 1 .............................................................................................................................................. 68

Result ..................................................................................................................................................... 68



G. Glossary ................................................................................................................................................. 69

H. Quizzes’ Answers ................................................................................................................................... 98



About “+W - Technology Skills For Women” series

Study Notes in the field of technology will be put together under this category for the following reasons:

to encourage ladies, who wish to do so, to stand up and look over the fence into technology related

topics;

with apprehension or fear;

and perhaps consider embracing a career move into this technological path;

or simply as to broaden their general knowledge; after all ICT is in most aspects of everyday life;

no matter the decision, their skills, professional strengths, and contribution can only be something

positive for technical and technological fields.



Sources:

How To Set Up A Home Network, Samara Lynn February 2, 2012, PCMag.com, http://www.pcmag.com/article2/0,2817,2375207,00.asp

Chapter 1: Building a Simple Network, Stephen McQuerry, Network World May 29, 2008, Cisco Press http://www.networkworld.com/subnets/cisco/053008-ch1-ccna-prep-library.html

Designing and Building the Best Small Office Network From the Ground Up, 2014, Marshall Breeding,, Network Computing, http://www.networkcomputing.com/netdesign/soho1.html

CCNA Certification Library (CCNA Self-Study, exam #640-801) 2003, Wendell Odom, Ciscopress, 1587200953

CCNA INTRO Exam Certification Guide 2003, Wendell Odom, Cisco Press, 1-58720-094-5

http://www.pcmag.com/article2/0,2817,2375207,00.asp

http://www.networkworld.com/subnets/cisco/053008-ch1-ccna-prep-library.html

http://www.networkcomputing.com/netdesign/soho1.html



Building a Simple Network

Sections:

A. Application sharing through networks B. Understanding binary basics C. Using a PC on a network D. Working with PC technology E. OSI model layers and functions F. Working with the OSI model

Learning Objectives:

Topic Name When you have completed this topic, you should be able to

Application sharing through networks

identify the major components of a computer system and their functionality, and list the resources required to install a NIC.

Understanding binary basics

distinguish between the processes used to convert between decimal, binary, and hexadecimal numbering systems.

Using a PC on a network identify the main purposes and functions of networking.

Working with PC technology

identify the purpose of major computer components, and calculate conversions between binary, decimal, and hexadecimal numerical systems.

OSI model layers and functions

distinguish between the OSI reference model and the TCP/IP stack.

Working with the OSI model

distinguish between basic computer and networking terms, and between the principles of the OSI reference model and the TCP/IP protocol stack.



A. Application sharing through networks

After completing this topic, you should be able to identify the major components of a computer system and their functionality, and list the resources required to install a NIC.

1. Major components of a computer system

2. Network interface card

Summary

1. Major components of a computer system

There are several fundamental elements involved in the networking of computers, including computers themselves and their components that are designed for network connectivity, as well as other network devices, such as bridges, hubs, and routers.

Some of the major hardware elements of computers that allow network connectivity include the central processing unit (CPU), the bus, drives, memory components, ports, and cards.

Many networking devices are special-purpose computers and have many of the same parts as normal PCs. For you to be able to use the computer as a reliable means of obtaining information, it must be in good working order.

If the need arises to troubleshoot a simple hardware or software problem, you should be able to recognize, name, and state the purpose of PC components.

Drives



CPU Expansion slots Bus Backplane components Motherboard

Drives

There are different drive types – for example the CD-ROM drive, the floppy disk drive, and the hard disk drive.

The CD-ROM drive is a compact disc read-only memory drive that can read information from a CD-ROM (combined CD-ROM/DVD-ROM are used nowadays). The floppy disk drive is a disk drive that can read and write to floppy disks (rarely used nowadays). The hard disk drive is the device that reads and writes data on a hard disk.

CPU

The CPU is the "brain" of the computer, where most of the calculations take place. The microprocessor is a silicon chip contained within a CPU.

Expansion slots



The expansion slots are openings in a computer into which you can insert a circuit board to add new capabilities to the computer. The expansion card is a printed circuit board that provides added capabilities to the computer.

Bus

A bus is a collection of wires through which data is transmitted from one part of a computer to another. The bus connects all the internal computer components to the CPU. The Industry-Standard Architecture (ISA) and the Peripheral Component Interconnect (PCI) are two types of buses.

Backplane components

The backplane is an area of the computer into which you plug external devices.

The following items are backplane components of a PC: - interface - mouse port - network card - parallel port



- power cord - serial port - sound card - video card The interface is a piece of hardware, such as a modem connector, that allows two devices to be connected together. The mouse port is a port that is designed for connecting a mouse to a PC. The network card is an expansion board inserted into a computer to enable connection to a network. The parallel port is an interface capable of transferring more than one bit simultaneously, and is used for connecting external devices, such as printers. The power cord is a cord connecting an electrical device to an electrical outlet to provide power to the device. The serial port is an interface that can be used for serial communication in which only one bit is transmitted at a time. The sound card is an expansion board that handles sound functions. The video card is a board that plugs into a PC to give it display capabilities.

Motherboard

The motherboard is the main circuit board of a computer.

The motherboard utilizes the following primary components: - power supply - printed circuit board (PCB) - random access memory (RAM) - read-only memory (ROM) - system unit The power supply is the component that supplies power to a computer. The printed circuit board (PCB) is a thin plate on which chips (integrated circuits) and other electronic components are placed.



Random access memory (RAM) is memory that has new data written into it as well as stored data read from it. It is also known as read-write memory. A drawback of RAM is that it requires electrical power to maintain data storage. If the computer is turned off or loses power, all data stored in RAM is lost unless the data was previously saved to disk. The read-only memory (ROM) is the computer memory on which data has been prerecorded. The system unit is the main part of a PC. It is a term that encompasses the chassis, the microprocessor, the main memory, the bus, and the ports. The system unit does not include the keyboard, the monitor, or any other external devices connected to the computer.

Because computers are important building blocks in a network, you should be able to identify their major components.

Questioni

Match the PC components to their descriptions.

Options:

1. Backplane 2. Bus 3. CPU 4. Expansion slots 5. Floppy drive (rarely used nowadays).

Targets:

a. A disk drive that can read and write to floppy disks b. A part of the computer that allows external devices to be connected c. Where most of the calculations take place d. Connects all the internal computer components to the CPU e. Openings in a computer into which you can insert a circuit board

Laptop computers and notebook computers have become very popular. There are few differences between the two. The main difference between PCs and laptops is that laptop components are smaller than those found in a



PC, they are designed to fit together into a smaller physical space, and they use less power when operated. These smaller components can be difficult to remove.

In a laptop, the expansion slots become Personal Computer Memory Card International Association (PCMCIA) card slots, or PC slots, through which NICs, modems, hard drives, and other useful devices (usually the size of a thick credit card) are connected.

PCs are more powerful than laptops, but laptops have the advantage of being portable, which makes it more convenient to work from home and while traveling between offices.

Quizii

What are the main differences between the components of a desktop PC and a laptop?

Options:

1. It is easier to remove the components from a laptop than the components from a PC 2. Laptops use less power than PCs 3. Laptop components are smaller than those in a PC 4. The slots you connect devices to are called expansion slots in a PC and PCMCIA slots in a laptop

2. Network interface card

A network interface card (NIC) is a printed circuit board that provides network communication capabilities to and from a personal computer.

Also called a LAN adapter, the NIC plugs into a motherboard and provides a port for connecting to the network. The NIC constitutes the computer interface with the local area network (LAN).



The NIC communicates with the network through a serial connection, and with the computer through a parallel connection.

When a NIC is installed in a computer, it requires an interrupt request line (IRQ), an input/output (I/O) address, a memory space for the operating system (such Windows), and drivers in order to perform its function.

An IRQ is a signal that informs a CPU that an event needing its attention has occurred. An IRQ is sent over a bus line to the microprocessor. An example of an interrupt request being issued is when a key is pressed on a keyboard, and the CPU must move the character from the keyboard to RAM.

An I/O address is a location in memory used by an auxiliary device to enter or retrieve data from a computer.

When selecting a NIC for a network, you should consider the following:

type of network type of media type of expansion slot

type of network

You must choose a NIC to suit the type of network you have. Ethernet NICs are designed for Ethernet LANs.

type of media

The type of port or connector used by the NIC for network connection is specific to the type of media, such as twisted-pair.



type of expansion slot

With regard to the type of expansion slot to use, you should consider that because PCI slots are faster than ISA slots, the latter are being phased out.

Quiziii

Which of the following should you take into account when selecting a NIC for a network?

Options:

1. The type of CPU 2. The type of media 3. The type of network 4. The type of expansion slot

The ability to install a NIC correctly is an important aspect of preparing a computer for network connectivity.

To install a NIC, you must know about the following:

Network card configuration Network card diagnostics Hardware resource conflicts

Network card configuration

You must know how the network card is configured, including jumpers, "plug-and-play" software, and erasable programmable read-only memory (EPROM).



Network card diagnostics

You must know the network card diagnostics, including the vendor-supplied diagnostics and loopback tests (see the documentation that comes with the card).

Hardware resource conflicts

You must know how to resolve hardware resource conflicts, including IRQ, I/O base address, and direct memory access (DMA), which is used to transfer data from RAM to a device without going through the CPU.

Quiziv

Which options correctly describe the information needed to install a NIC?

Options:

1. Knowledge of how to resolve hardware resource conflicts 2. Knowledge of all types of network cards 3. Knowledge of how the network card is configured 4. Knowledge of how to use the network card diagnostics

Summary

There are several PC components, which include the motherboard, the backplane, the central processing unit (CPU), the bus, drives, expansion slots, memory components, ports, and cards. A laptop is a portable PC that uses smaller components, is more power efficient than a PC, and has Personal Computer Memory Card International Association (PCMCIA) card slots instead of expansion slots. A network interface card (NIC) is a circuit board that allows a personal computer to communicate with a network. You need to consider the type of network, media, and expansion slot when selecting a NIC. To install a NIC, you should know how to configure it, how to use its diagnostics, and be able to resolve hardware resource conflicts.



B. Understanding binary basics

After completing this topic, you should be able to distinguish between the processes used to convert between decimal, binary, and hexadecimal numbering systems.

1. Bits, bytes and measurement terms

2. Conversion between decimal and binary

3. Conversion between binary and hexadecimal

Summary

1. Bits, bytes and measurement terms

At the most basic level, computers perform their computations by using 1s and 0s instead of the decimal system.

Computers are made up of electronic switches. At the lowest levels of computation, computers depend on these electronic switches to make decisions. Computers react only to electrical impulses, understood by the computer as either "on" or "off" states (1s or 0s).

Computers can understand and process only data that is in a binary format, represented by 0s and 1s. These 0s and 1s represent the two possible states of an electrical impulse and are referred to as binary digits (bits).

Most computer coding schemes use eight bits to represent a number, letter, or symbol. A series of eight bits is referred to as a byte. One byte represents a single addressable storage location.



The following are commonly used computer measurement terms:

Bit (b) Byte (B) Kilobit (Kb) Kilobyte (KB) Megabit (Mb) Megabyte (MB) Gigabit (Gb) Gigabyte (GB)

Bit (b)

A bit is the smallest unit of data in a computer. A bit equals 1 or 0 in the binary format in which data is processed by computers. Bits per second (bps) is a standard unit of measurement for data transmission.

Byte (B)

A byte is a unit of measure used to describe the size of a data file, the amount of space on a disk or other storage medium, or the amount of data being sent over a network. One byte equals eight bits of data. Bytes per second (Bps) is a standard unit of measurement of the data transmission rate over a network connection.

Kilobit (Kb)

A kilobit is approximately 1000 bits (1024 bits exactly). Kilobits per second (Kbps) is a standard unit of measurement of the data transmission rate over a network connection.



Kilobyte (KB)

A kilobyte is approximately 1000 bytes (1024 bytes exactly). Kilobytes per second (KBps) is another standard unit of measurement for data transmission.

Megabit (Mb)

A megabit is approximately 1 million bits. Megabits per second (Mbps) is a standard unit of measurement of the data transmission rate over a network connection.

Megabyte (MB)

A megabyte is approximately 1 million bytes (1,048,576 bytes exactly). A megabyte is sometimes referred to as a "meg." Megabytes per second (MBps) is a standard unit of measurement for data transmission.

Gigabit (Gb)

A gigabit is equal to approximately one billion bits. Gigabits per second (Gbps) is a standard unit of measurement of the data transmission rate over a network connection.

Gigabyte (GB)

A gigabyte is equal to approximately one billion bytes. Gigabytes per second (GBps) is a standard unit of measurement for data transmission.

It is a common error to confuse KB with Kb and MB with Mb. You should remember to do the proper calculations when comparing transmission speeds that are measured in KBps and those measured in Kbps. For example, modem software usually shows the connection speed in kilobits per second (for example, 45 Kbps). However, popular browsers display file-download speeds in kilobytes per second, meaning that with a 45-Kbps connection, the download speed would be a maximum of 5.76 KBps. In practice, this download speed cannot be reached because of other factors consuming bandwidth at the same time.



The following are speed measurement terms commonly used for microprocessors:

Hz MHz GHz

Hz

A hertz (hz) is a unit of frequency. It is the rate of change in the state or cycle in a sound wave, alternating current, or other cyclical waveform. It represents one cycle per second and is used to describe the speed of a computer microprocessor.

MHz

A megahertz (MHz) represents one million cycles per second. This is a common unit of measurement of the speed of a processing chip, such as a computer microprocessor.

GHz

A gigahertz (GHz) represents one billion (1,000,000,000) cycles per second. This is a common unit of measurement of the speed of a processing chip, such as a computer microprocessor.

PC processors are getting faster all the time. The microprocessors used on PCs in the 1980s typically ran under 10 MHz (the original IBM PC was 4.77 MHz). Today they are measured in GHz.

Quizv

Match the measurement terms with their definitions.

Options:

1. Bit 2. Byte 3. GB 4. KB 5. Mb 6. MB



Targets:

a. It equals 1 or 0 in binary format b. It is equal to 8 bits c. It is equal to approximately 1000 bytes d. It is equal to approximately one billion bytes e. It is equal to approximately one million bits f. It is equal to approximately one million bytes

2. Conversion between decimal and binary

Converting a decimal number to a binary number is one of the most common procedures performed in computer operations.

Computers recognize and process data using the binary, or base 2, numbering system. The binary numbering system uses only two symbols (0 and 1) instead of the ten symbols used in the decimal numbering system.

The position, or place, of each digit represents the number 2 (the base number) raised to a power (exponent), based on its position (2^0, 2^1, 2^2, 2^3, 2^4, and so on).



Suppose you want to convert the decimal number 253 to a binary number. You can do this by dividing the number by two each time and taking note of the remaining number.

First you divide 253 by 2, which is equal to 126 with 1 remaining.

Then you divide 126 by 2, which is equal to 63 with 0 remaining.






Finally you divide 1 by 2, which is equal to 0 with 1 remaining.

You should write the binary number in the order of the last bit first. In this case, the binary equivalent of 253 is 11111101.

Suppose you want to convert the decimal number 153 to binary.

Suppose you want to convert the number 35 to a binary number. You can do this using the following steps:

Step 1 Step 2 Step 3 Step 4 Step 5



Step 1

Step 1: Looking at the figure, you must identify what is the greatest power of 2 that is less than or equal to 35. Starting with the largest number, 2^5 (32) is smaller than 35. You place a "1" in that column, a "0" in each preceding place, and calculate how much is left over by subtracting 32 from 35. The result is 3.

Step 2

Step 2: Next you check to see if 16 (the next lower power of 2) fits into 3. Because it does not, a "0" is placed in that column. The value of the next number is 8, which is larger than 3, so a "0" is placed in that column too.

Step 3

Step 3: The next value is 4, which is still larger than 3, so it too receives a "0."

Step 4

Step 4: The next value is 2, which is smaller than 3. Because 2 fits into 3, place a "1" in that column. Now subtract 2 from 3, and the result is 1.

Step 5

Step 5: The value of the last number is 1, which fits in the remaining number. Therefore, you place a "1" in the last column. The binary equivalent of the decimal number 35 is 100011.

In this case, the place values of 128 and 64 are too high to be considered for the calculation.



Quizvi

Which number is the binary equivalent of 197?

Options:

1. 10000101 2. 10100101 3. 11000101 4. 11100101

You can also convert binary numbers to decimal format. As with decimal-to-binary conversion, there is usually more than one way to convert binary numbers to decimal numbers.

The figure illustrates one conversion method. Each binary digit has a corresponding decimal position value. To work out the decimal position values, you start with 1 and then multiply each number by 2.

For example, 1 multiplied by 2 is equal to 2, 2 multiplied by 2 is 4, 4 multiplied by 2 is 8, and so on.

Consider the 8 digits that make up the binary number. If a digit is 1, then you count the corresponding position value whereas if the digit is 0, then you ignore it.



Next, suppose you want to convert the binary number 10111001 to a decimal number. You can do this using the following steps:

Step 1 Step 2 Step 3 Step 4 Step 5

Step 1

Step 1: The binary number has a 1 in the 2^7 (128) bit position, so 128 is added to the decimal total.

Step 2

Step 2: Next the binary number has a 0 in the 2^6 (64) bit position so 64 is not added to the decimal total (128+0=128). Next there is a 1 in the 2^5 (32) bit position, so the decimal total becomes 128+32=160.

Step 3

Step 3: Next there is a 1 in the 2^4 (16) bit position. Adding the value to the decimal total gives 160+16=176. Then the 2^3 (8) bit position has the binary digit 1, so the value 8 needs to be added to the decimal total: 176+8=184.

Step 4

Step 4: Next there are 0s in the 2^2 and 2^1 bit positions, so you add 0s to the decimal total: 184+0+0=184.

Step 5



Step 5: Finally, there is a 1 in the 2^0 (1) bit position, so you add 1 to 184 to give the result 185. The decimal equivalent of the binary number 10111001 is 185.

Quizvii

Convert the binary number 11011000 to decimal.

3. Conversion between binary and hexadecimal

The base 16, or hexadecimal (hex), numbering system is used frequently when working with computers because it can be used to represent binary numbers in a more readable form. The computer performs computations in binary, but there are instances when the binary output of a computer is expressed in hexadecimal format to make it easier to read.

Converting a hexadecimal number to binary, and vice versa, is a common task when dealing with the 16-bit configuration register in Cisco routers. That 16-bit binary number can be represented as a four-digit hexadecimal number. For example, 0010000100000010 in binary is equal to 2102 in hex.

The most common way for computers and software to express hexadecimal output is using "0x" in front of the hexadecimal number. Thus, whenever you see "0x," you know that the number that follows is a hexadecimal number. For example, 0x1234 means 1234 in base 16.

It is referred to as base 16 because it uses 16 symbols. Combinations of these symbols can represent all possible numbers. Because there are only 10 symbols that represent digits (0, 1, 2, 3, 4, 5, 6, 7, 8, 9) and base 16 requires six more symbols, the extra symbols are the letters A, B, C, D, E, and F.



The "A" represents the decimal number 10, "B" represents 11, "C" represents 12, "D" represents 13, "E" represents 14, and "F" represents 15.

The position of each symbol (digit) in a hex number represents the base number 16 raised to a power (exponent) based on its position. Moving from right to left, the first position represents 16^0 (or 1), the second position represents 16^1 (or 16), the third position represents 16^2 (or 256), and so on.

Network layer 2 MAC addresses are typically written in hex. For Ethernet and Token Ring topologies, these addresses are 48 bits, or six octets (one octet is eight bits). Because these addresses consist of six distinct octets, you can write them as 12 hex numbers.

Instead of writing 10101010.11110000.11000001.11100010.011101 11.01010001 you can write the much shorter hex equivalent: AA.F0.C1.E2.77.51. To make handling hex versions of MAC addresses even easier, the dots are placed only after each four hex digits, as in AAF0.C1E2.7751.



Converting binary to hex is easy because base 16 (hexadecimal) is a power of base 2 (binary). Every four binary digits (bits) are equal to one hexadecimal digit.

The table compares the binary and hexadecimal numbering systems.

If there is a binary number that looks like 01011011, you can break it into two groups of four bits: 0101 and 1011. When converting these two groups to hex, they become 5 and B, so the hexadecimal equivalent of the binary 01011011 is 5B.

No matter how large the binary number, you always apply the same conversion. First you start from the right of the binary number and break the number into groups of four.

If the far left group does not contain four digits, add zeros to the left end until there are four digits (bits) in every group.

Then you convert each group of four to its hex equivalent.



Suppose you want to convert the binary number 01001110000100110101011110001101 to hexadecimal.

Quizviii

Which options are hexadecimal equivalents of 1010110100010011111000111101100?

Options:

1. 1451880940 2. 5689F1EC 3. AD13E3D4 4. 0x5689F1EC

You can also convert hexadecimal numbers to binary format. To convert from hexadecimal to binary, you convert every hex digit into four binary digits (bits).

For example, to convert hex AC (0xAC) to binary, you first convert hex A, which is 1010 binary, and then convert hex C, which is 1100 binary. So the conversion of hex AC is 10101100 binary.



Suppose you want to convert the hexadecimal number 1245F7DC9 to binary.



Make sure you include four binary digits for each hexadecimal character, adding zeros to the left of the number when necessary.

Quizix

Match the binary numbers to their hexadecimal equivalent.

Options:

1. 1100011101011000010 2. 10101101110110101000101 3. 10100101010110001000101000100100011 4. 1011000100111111110

Targets:

a. 52AC45123 b. 56ED45 c. 589FE d. 63AC2



Summary

The binary numbering system is made up of 0s and 1s. The most common measurement terms are bit, byte, kilobit (Kb), kilobyte (KB), megabit (Mb), megabyte (MB), gigabit (Gb), and gigabyte (GB). The microprocessor speeds are hertz (Hz), megahertz (MHz), and gigahertz (GHz). The decimal numbering system uses ten symbols – 0 - 9. Decimal numbers can be converted to binary. One way of doing this is to divide the decimal number by two each time, taking note of the remaining number. All the remaining numbers form the binary equivalent. You can also convert binary numbers to decimal. The hexadecimal numbering system uses 16 symbols – 0 - 9, and A - F. Hexadecimal numbers often have 0x in front of them. You can easily convert binary numbers to hexadecimal as each group of four binary digits is equal to one hexadecimal digit. You can also convert hexadecimal numbers to binary by converting every hex digit into four binary digits (bits).



C. Using a PC on a network

To review basic networking technologies and common network applications, and identify the main purposes and functions of networking.

1. Basic Networking Terminology

2. Network Applications

3. Computer Networks

Summary

1. Basic Networking Terminology

Computer networking, like most industries, has its own jargon, which includes technical terms, abbreviations, and acronyms. Without a good grasp of the terminology, it will be difficult to understand the concepts and processes involved in networking. The following list of terms and their definitions is intended to be a quick reference that defines some of the most important words, phrases, and acronyms related to computer networking:

A network interface card (NIC), pronounced "nick," is also called the LAN adapter, or just the network interface. This card typically goes into an ISA, PCI, or PCMCIA (PC card) slot in a computer and connects to the network medium. It then connects to other computers through the network media.

Media refers to the various physical environments through which transmission signals pass. Common network media include twisted-pair, coaxial, and fiber-optic cable, and even the earth's atmosphere through which wireless transmission occurs.

A protocol is a set of rules. In the case of a network protocol, it is a set of rules by which computers communicate. The term "protocol suite" describes a set of several protocols that perform different functions related to different aspects of the communication process.

Cisco IOS software which runs on Cisco equipment and devices, is the industry-leading and most widely deployed network system software. It delivers intelligent network services for enabling the rapid deployment of Internet applications.

Cisco IOS software provides a wide range of functionality, from basic connectivity, security, and network management to technically advanced services. The functionality of Cisco IOS software is the result of a technological evolution. First-generation networking devices could only store and forward data packets.

Today, Cisco IOS software can recognize, classify, and prioritize network traffic, optimize routing, support voice and video applications, and much more. Cisco IOS software runs on most Cisco routers and Cisco switches. These network devices carry most of the Internet traffic today.

Network operating system (NOS) usually refers to server software such as Windows NT, Windows 2000 Server, Windows Server 2003, Novell NetWare, UNIX, and Linux. The term sometimes refers to the networking components of a client operating system such as Windows 95 or the Macintosh OS.

Connectivity devices refer to several different device types, all of which are used to connect cable segments, connect two or more smaller networks (or subnets) into a larger network, or divide a large network into smaller ones. The term encompasses repeaters, hubs, switches, bridges, and routers.



The following are three categories of networks:

A local-area network (LAN) is a network that is confined to a limited geographic area. This area can be a room, a floor, a building, or even an entire campus.

A metropolitan-area network (MAN) is a network that is larger in size than a LAN and smaller in size than a WAN. This is a network that covers approximately the area of a large city or metropolitan area.

A wide-area network (WAN) is made up of interconnected LANs. It spans wide geographic areas by using WAN links such as telephone lines or satellite technology to connect computers in different cities, countries, or even different continents.

Network structure is described in the following two ways:

The logical topology is the path that the signals take from one computer to another. The logical topology may or may not correspond to the physical topology. For instance, a network can be a physical "star," in which each computer connects to a central hub, but inside the hub the data can travel in a circle, making it a logical "ring."

The physical topology refers to the layout or physical shape of the network, and includes the topologies in this table.

Topologies

Bus Computers arranged so that cabling goes from one to another in a linear fashion

Ring When there are no clear beginning points or endpoints within a topology, forming a circle

Star If the systems "meet in the middle" by connecting to a central hub

Mesh When multiple redundant connections make pathways to some or all of the endpoints

2. Network Applications

Network applications are software programs that run between different computers connected together on a network.

Some of the more common uses of network applications include using a web browser program to find content from the World Wide Web, or using an e-mail program to send e-mails over the Internet.



Network applications are selected based on the type of work that needs to be done. A complete set of application-layer programs is available to interface with the Internet. Each application program type is associated with its own application protocol. Some examples include:

HTTP is the World-Wide-Web communications protocol used to connect to web servers. Its primary function is to establish a connection with a web server and transmit HTML pages to the client browser.

Post Office Protocol 3 (POP3) is an application-layer protocol supported by e-mail programs for the retrieval of electronic mail. POP3 is a standard e-mail server commonly used on the Internet. It provides a message storage container that holds incoming e-mail until users log on and download their messages.

File Transfer Protocol (FTP) is a simple file utility program for transferring files between remote computers, which also provides for basic user authentication.

Telnet is a remote access application and protocol for connecting to remote computer consoles, which also provides for basic user authentication. Telnet is not a graphical user interface but is command-line driven or character mode only.

Simple Network Management Protocol (SNMP) is used by network management programs for monitoring the network device status and activities.

It is important to emphasize that the application layer is just another protocol layer in the OSI model or TCP/IP protocol stack. The programs interface with application layer protocols.

E-mail client applications, such as Microsoft Outlook, Lotus Notes, Pegasus Mail, Mozilla's Thunderbird, Eudora, KMail, all work with the POP (Post Office Protocol) and IMAP4 (Message Access Protocol) protocols.

Electronic mail enables you to send messages between connected computers. The procedure for sending an e-mail document involves two separate processes – sending the e-mail to the user's post office, which is a computer running the POP3 server software, and delivering the e-mail from that post office to the user's e-mail client computer, which is the recipient.

While popular protocols for retrieving mail include POP3 and IMAP4, sending mail is usually done using the SMTP protocol.

A user's mailbox can be accessed in two dedicated ways. POP allows the user to download messages one at a time and only deletes them from the server after they have been successfully saved on local storage. It is possible to leave messages on the server to permit another client to access them.

Alternatively, IMAP allows users to keep messages on the server, flagging them as appropriate. IMAP provides folders and sub-folders, which can be shared among different users with possibly different access rights.

Another important standard supported by most email clients is MIME, which is used to send binary file email attachments. Attachments are files that are not part of the email proper, but are sent with the email.



The same principle is true with web browsers. The two most popular web browsers are Google Chrome, Mozilla Firefox, Internet Explorer, Opera, and Safari. The appearance of these web browser programs might be different, but they both work with the application layer HTTP protocol.

3. Computer Networks

One of the primary purposes of a network is to increase productivity by linking computers and computer networks, so that people have easy access to information regardless of differences in time, place, or type of computer system.

Because companies have adopted networks as part of their business strategy, they typically subdivide and map corporate networks to the corporate business structure. In the figure, the network is defined based on the grouping of employees (users) into a main office and various remote access locations.

A main office is a site where everyone is connected via a LAN and where the bulk of corporate information is located. A main office can have hundreds or even thousands of people who depend on network access to do their jobs. It may have several LANs, or it may be a campus that contains several buildings. Because everyone needs access to central resources and information, it is common to see a high-speed backbone in a LAN as well as a data center with high-performance computers or servers and networked applications.

A variety of remote access locations connect to the main office or each other using WAN services as follows:

In branch offices, smaller groups of people work and connect to each other via a LAN. To connect to the main office, these users must use WAN services such as Asymmetric digital subscriber line (ADSL). Although some corporate information may be stored at a branch office, it is more likely that branch offices have local network resources, such as printers, but have to access information directly from the main office.

A home office is where individuals are set up to work from their own home. Home office workers most likely require on-demand connections to the main office or a branch office to access information or use network resources such as file servers.

Individuals who are mobile users connect to the main office LAN when they are at the main office, at the branch office, or on the road. Their network access needs are based on where they are located.

In order to understand what types of equipment and services to deploy in a network and when to deploy them, it is important to understand the business and user needs. The figure shows how to map an organization's business or user requirements to a network.



In this example, the business needs may require LAN connectivity within the campus to interconnect the servers and end-user PCs, and WAN connectivity to connect the campus to the remote branch office and telecommuters. The WAN connection to the remote branch office requires a permanent connection, such as a leased line, and the home office connection requires a dial-up connection, such as ADSL.

Asymmetric digital subscriber line (ADSL) is a type of digital subscriber line (DSL) technology, a data communications technology that enables faster data transmission over copper telephone lines than a conventional voice band modem can provide. It does this by utilizing frequencies that are not used by a voice telephone call. A splitter, or DSL filter, allows a single telephone connection to be used for both ADSL service and voice calls at the same time. ADSL can generally only be distributed over short distances from the telephone exchange (the last mile), typically less than 4 kilometres (2 mi).

At the telephone exchange the line generally terminates at a digital subscriber line access multiplexer (DSLAM) where another frequency splitter separates the voice band signal for the conventional phone network. Data carried by the ADSL are typically routed over the telephone company's data network and eventually reach a conventional Internet Protocol network.

A digital subscriber line access multiplexer (DSLAM) is a network device, often located in telephone exchanges, that connects multiple customer digital subscriber line (DSL) interfaces to a high-speed digital communications channel using multiplexing techniques.



Summary

When working with computer applications, it is important that you are familiar with networking terminology. There are three categories of networks – a LAN, a MAN, and a WAN. The physical topology of a network is the physical structure of a network. The logical topology of a network is the path that signals follow through the network.

Network applications are software programs that run between different computers connected on a network. Each application type has associated protocols depending on the function of the application. HTTP is used by applications that access the Internet, POP3 is used by applications that access email services, FTP is used by applications that transfer files, Telnet is used by applications that remotely access other machines, and SNMP is used by applications that monitor the operation of the network.

Applications interface with protocols in the application layer of the OSI model or TCP/IP stack.

By creating a computer network, you enable access between computers regardless of time, place, or type of computer system. Because networks are incorporated into the business strategy of a company, a company's network will usually replicate its business structure. Typically, a network will be subdivided to facilitate the branch, home, and main office of the company as well as its mobile users.



D. Working with PC technology

After completing this topic, you should be able to identify the purpose of major computer components, and calculate conversions between binary, decimal, and hexadecimal numerical systems.

1. Exercise overview

2. Task 1: Identifying PC components

3. Task 2: Interpreting numerical systems

1. Exercise overview

In this exercise, you're required to identify the internal components of a PC and calculate conversions between the three numerical systems – binary, decimal, and hexadecimal.

This involves the following tasks:

identifying PC components converting between numerical systems

2. Task 1: Identifying PC components

Let's look at the internal components of a PC.



Step 1 of 1

Match the PC components to their descriptions.

Options:

1. CD Rom drive 2. Hard disk drive 3. RAM 4. NIC 5. CPU

Targets:

a. A compact disk read-only memory drive b. A device that reads and writes data on a hard disk c. An expansion board inserted into a computer to enable connection to a network d. A silicon-based microprocessor where most of the computer's calculations take place e. Memory that has new data written into it and has stored data read from it

Resultx

A CD Rom drive is a compact disk read-only memory drive, a hard disk drive is a device that reads and writes data on a hard disk, RAM is memory that has new data written into it and stored data read from it, a NIC is an expansion board inserted into a computer to enable connection to a network, and a CPU is a silicon-based microprocessor where most of the computer's calculations take place.

A CD-ROM drive can read information from a CD-ROM disk.

A hard disk drive reads data from a hard disk. Unlike a CD-ROM drive it can also write data to a disk.

RAM is also known as read-write memory.

The NIC plugs into a motherboard and provides a port for connecting to the network. It is also known as a LAN adapter.

A CPU acts as the "brain" of the computer.

3. Task 2: Interpreting numerical systems

Let's look at the binary, decimal, and hexadecimal numerical systems.



Step 1 of 5

Match the numerical systems to their descriptions.

Options:

1. Binary 2. Decimal 3. Hexadecimal

Targets:

a. This system uses 16 symbols b. This system uses 10 symbols c. This system uses 2 symbols

Resultxi

Binary uses 2 symbols, decimal uses 10 symbols, and hexadecimal uses 16 symbols.

The binary system uses 2 symbols – 0 and 1 – and is also known as base 2.

The decimal system uses 10 symbols – 0 to 9 – and is also known as base 10.

The hexadecimal system uses 16 symbols – 0-9, A-F – and is also known as base 16.

Let's look at some binary conversions.



Step 2 of 5

See if you can convert the binary number 10101000 to decimal.

Resultxii

The decimal equivalent of the binary number 10101000 is 168.

Step 3 of 5

What is the hexadecimal equivalent of 100011000101111?

Options:

1. 462C 2. 462D 3. 462E 4. 462F

Result

The hexadecimal equivalent of 100011000101111 is 462F.

Option 1 is incorrect. 462C is actually the hexadecimal equivalent of 100011000101100.

Option 2 is incorrect. 462D is actually the hexadecimal equivalent of 100011000101101.

Option 3 is incorrect. 462E is actually the hexadecimal equivalent of 100011000101110.

Option 4 is correct. 462F is the hexadecimal equivalent of 100011000101111 – 100 is 4, 0110 is 6, 0010 is 2, and 1111 is F.

Let's look at a conversion from decimal to binary.



Step 4 of 5

See if you can convert the decimal number 68 to binary.

Result

The decimal number 68 is 1000100 in binary.

Let's look at a conversion from hexadecimal to binary.

Step 5 of 5

What is the binary equivalent of 812C?

Options:

1. 1000000100101011 2. 1000000100101100 3. 1000000100101101 4. 1000000100101110

Result

The binary equivalent of 812C is 1000000100101100.

Option 1 is incorrect. 1000000100101011 is actually the binary equivalent of 812B.

Option 2 is correct. 1000000100101100 is actually the binary equivalent of 812C – 8 is 1000, 1 is 0001, 2 is 0010, and 1100 is C.

Option 3 is incorrect. 1000000100101101 is actually the binary equivalent of 812D.

Option 4 is incorrect. 1000000100101110 is actually the binary equivalent of 812E.



E. OSI model layers and functions

After completing this topic, you should be able to distinguish between the OSI reference model and the TCP/IP stack.

1. Origins of the OSI reference model

2. OSI layers and functions

3. Data communications

4. The TCP/IP protocol stack

Summary

1. Origins of the OSI reference model

The early development of LANs, MANs, and WANs was chaotic in many ways. The early 1980s saw tremendous increases in the number and sizes of networks.

As companies realized that they could save money and gain productivity by using networking technology, they added networks and expanded existing networks as rapidly as new network technologies and products were introduced.

By the middle of the 1980s, companies began to experience difficulties from all the expansions they had made. It became more difficult for networks using different specifications and implementations to communicate with each other. The companies realized that they needed to move away from proprietary networking systems, those systems which are privately developed, owned, and controlled.

A standard or technology may be

proprietary open

proprietary

Proprietary means that one company or a small group of companies control(s) all usage of the technology. In the computer industry, proprietary is the opposite of open.



open

Open means that free usage of the technology is available to the public.

To address the problem of networks being incompatible and unable to communicate with each other, the International Organization for Standardization (ISO) researched different network schemes. As a result of this research, the ISO created a model that would help vendors create networks that would be compatible with, and operate with, other networks.

The Open Systems Interconnection (OSI) reference model, released in 1984, was the descriptive scheme that the ISO had created. It provided vendors with a set of standards that ensured greater compatibility and interoperability between the various types of network technologies produced by companies around the world.

Although other models exist, most network vendors today relate their products to the OSI reference model, especially when they want to educate customers on the use of their products. It is considered the best tool available for teaching people about sending and receiving data on a network.

The OSI reference model has seven numbered layers, each illustrating a particular network function. This separation of networking functions is called layering.



The OSI reference model defines the network functions that occur at each layer.

More importantly, the OSI reference model facilitates an understanding of how information travels throughout a network.

In addition, the OSI reference model describes how data travels from application programs (for example, spreadsheets), through a network medium, to an application program located in another computer, even if the sender and receiver are connected using different network media.

Quiz

Which of the following statements about the OSI model are correct.

Options:

1. It defines the network functions that occur at each layer 2. It is a conceptual framework that specifies how information travels through networks 3. It is a model that describes how data makes its way from one application program to another

throughout a network 4. It was developed in order to help companies communicate with each other using proprietary

network systems.

Answerxiii

(See Endnotes).



2. OSI layers and functions

The practice of moving information between computers is divided into seven techniques in the OSI reference model. Each of the seven techniques is represented by its own layer in the model.

The seven layers of the OSI reference model are as follows:

Layer 7: Application layer Layer 6: Presentation layer Layer 5: Session layer Layer 4: Transport layer Layer 3: Network layer Layer 2: Data-link layer Layer 1: Physical layer

Dividing the network into seven layers provides the following advantages:

accelerates evolution ensures interoperable technology facilitates modular engineering reduces complexity standardizes interfaces simplifies teaching and learning

accelerates evolution

Layering accelerates evolution by providing for effective updates and improvements to individual components without affecting other components or having to rewrite the entire protocol.

ensures interoperable technology

Layering prevents changes in one layer from affecting the other layers, allowing for quicker development, and ensuring interoperable technology.

facilitates modular engineering

Layering allows different types of network hardware and software to communicate with each other, thereby facilitating modular engineering.

reduces complexity

Layering breaks network communication into smaller, simpler parts and reduces complexity.

standardizes interfaces



Layering standardizes network component interfaces to allow multiple-vendor development and support.

simplifies teaching and learning

Layering breaks network communication into smaller components to make learning easier, thereby simplifying teaching.

Each OSI layer contains a set of functions performed by programs to enable data packets to travel from a source to a destination on a network. Now we will look at each layer in the OSI reference model.

The application layer is the OSI layer that is closest to the user. This layer provides network services to the user's applications. It differs from the other layers in that it does not provide services to any other OSI layer, but rather, only to applications outside the OSI model. The application layer establishes the availability of intended communication partners and synchronizes and establishes agreement on procedures for error recovery and control of data integrity.

The presentation layer ensures that the information that the application layer of one system sends out is readable by the application layer of another system.

For example, a PC program communicates with another computer, one using extended binary coded decimal interchange code (EBCDIC) and the other using ASCII to represent the same characters. If necessary, the presentation layer translates between multiple data formats by using a common format.



The session layer establishes, manages, and terminates sessions between two communicating hosts. It provides its services to the presentation layer. The session layer also synchronizes dialogue between the presentation layers of the two hosts and manages their data exchange.

For example, web servers have many users, so there are many communication processes open at a given time. It is important to keep track of which user communicates on which path.

In addition to session regulation, the session layer offers provisions for efficient data transfer, class of service, and exception reporting of session layer, presentation layer, and application layer problems.

The transport layer segments data from the sending host's system and reassembles the data into a data stream on the receiving host's system.

For example, business users in large corporations often transfer large files from field locations to a corporate site.



Reliable delivery of the files is important, so the transport layer will break down large files into smaller segments that are less likely to incur transmission problems.

The boundary between the transport layer and the session layer can be thought of as the boundary between application protocols and data-flow protocols. Whereas the application, presentation, and session layers are concerned with application issues, the lower four layers are concerned with data transport issues.

The transport layer attempts to provide a data-transport service that shields the upper layers from transport implementation details. Specifically, issues such as reliability of transport between two hosts are the concern of the transport layer. In providing communication service, the transport layer establishes, maintains, and properly terminates virtual circuits. Transport error detection and recovery and information flow control are used to provide reliable service.

The network layer provides connectivity and path selection between two host systems that may be located on geographically separated networks. The growth of the Internet has increased the number of users accessing information from sites around the world, and it is the network layer that manages this connectivity.



The data-link layer defines how data is formatted for transmission and how access to the network is controlled.

The physical layer defines the electrical, mechanical, procedural, and functional specifications for activating, maintaining, and deactivating the physical link between end systems.

Characteristics such as voltage levels, timing of voltage changes, physical data rates, maximum transmission distances, physical connectors, and other similar attributes are defined by physical layer specifications.

In summary, the functions of the layers in the OSI model are as follows:

application network services data representation interhost communication end-to-end connections data delivery



media access binary transmission

application network services

The application layer provides network services to any applications requiring access to the network.

data representation

The presentation layer handles data representation. It ensures data is readable, and formats and structures data. It also negotiates data transfer syntax for the application layer.

interhost communication

The session layer provides interhost communication. In doing this it establishes, manages, and terminates sessions between applications.

end-to-end connections

The transport layer facilitates end-to-end communications. It handles transportation issues between hosts and ensures data transport reliability. It also establishes, maintains, and terminates virtual circuits, and provides reliability through fault detection and recovery information flow control.

data delivery

The network layer ensures data delivery. It provides connectivity and path selection between two host systems, routes data packets and selects the best path to deliver data.

media access

The data-link layer provides access to the network media. It defines how data is formatted and how access to the network is controlled.

binary transmission

The physical layer handles binary transmission. It defines the electrical, mechanical, procedural, and functional specifications for activating, maintaining, and deactivating the physical link. It is responsible for transmitting the data onto the physical media.



Quiz

What is the function of the session layer?

Options:

1. It routes data packets 2. It ensures reliable transport of data 3. It ensures received data is readable 4. It regulates communication processes

Answerxiv

(See Endnotes).

3. Data communications

All communications on a network originate at a source and are sent to a destination.

The information sent on a network is referred to as data or data packets. If one computer (Host A) wants to send data to another computer (Host B), the data must first be packaged by a process called encapsulation.

The encapsulation process can be thought of as putting a letter inside an envelope, and then properly writing the recipient's mail address on the envelope so it can be properly delivered by the postal system.

Encapsulation wraps data with the necessary protocol information before network transit. Therefore, as the data moves down through the layers of the OSI model, each OSI layer adds a header (and a trailer if applicable) to the data before passing it down to a lower layer.



The headers and trailers contain control information for the network devices and receiver to ensure proper delivery of the data and to ensure that the receiver can correctly interpret the data.

The figure illustrates how encapsulation occurs. It shows the manner in which data travels through the layers.

The following eight steps occur in order to encapsulate data:

Step 1 Step 2 Step 3 Step 4 Step 5 Step 6 Step 7 Step 8



Step 1

Step 1: The user data is sent from an application to the application layer.

Step 2

Step 2: The application layer adds the application layer header (Layer 7 header) to the user data. The Layer 7 header and the original user data become the data that is passed down to the presentation layer.

Step 3

Step 3: The presentation layer adds the presentation layer header (Layer 6 header) to the data. This then becomes the data that is passed down to the session layer.

Step 4

Step 4: The session layer adds the session layer header (Layer 5 header) to the data. This then becomes the data that is passed down to the transport layer.

Step 5

Step 5: The transport layer adds the transport layer header (Layer 4 header) to the data. This then becomes the data that is passed down to the network layer.

Step 6

Step 6:The network layer adds the network layer header (Layer 3 header) to the data. This then becomes the data that is passed down to the data-link layer.

Step 7

Step 7: The data-link layer adds the data-link-layer header and trailer (Layer 2 header and trailer) to the data. A Layer 2 trailer is usually the frame check sequence (FCS), which is used by the receiver to detect whether or not the data is in error. This then becomes the data that is passed down to the physical layer.

Step 8

Step 8:The physical layer then transmits the bits onto the network media.

Quiz

When a user sends information across a network it first traverses the application layer.

Rank the layers of the OSI model in the order in which encapsulation occurs, after the application layer.



Options

Option Description

A Data Link

B Network

C Physical

D Presentation

E Session

F Transport

Answerxv

(See Endnotes).

When the remote device receives a sequence of bits, the physical layer at the remote device passes the bits to the data-link layer for manipulation.

The data-link layer performs the following tasks:

Task 1 Task 2 Task 3 Task 4

Task 1

Task 1: It checks the data-link trailer (the FCS) to see if the data is in error.



Task 2

Task 2: If the data is in error, it may be discarded, and the data-link layer may ask for the data to be retransmitted.

Task 3

Task 3: If the data is not in error, the data-link layer reads and interprets the control information in the data-link header.

Task 4

Task 4: It strips the data-link header and trailer, and then passes the remaining data up to the network layer based on the control information in the data-link header.



This process is referred to as de-encapsulation. Each subsequent layer performs a similar de-encapsulation process. Think of de-encapsulation as the process of reading the address on a letter to see if it is for you or not, and then removing the letter from the envelope if the letter is addressed to you.

So that data packets can travel from the source to the destination, each layer of the OSI model at the source must communicate with its peer layer at the destination.

This form of communication is referred to as peer-to-peer communication. During this process, the protocols at each layer exchange information, called protocol data units (PDUs), between peer layers.

Data packets on a network originate at a source and then travel to a destination. Each layer depends on the service function of the OSI layer below it. To provide this service, the lower layer uses encapsulation to put the PDU from the upper layer into its data field. It then adds whatever headers the layer needs to perform its function. As the data moves down through Layers 7 through 5 of the OSI model, additional headers are added. The grouping of data at the Layer 4 PDU is called a segment.

The network layer provides a service to the transport layer, and the transport layer presents data to the internetwork subsystem. The network layer moves the data through the internetwork by encapsulating the data and attaching a header to create a packet (the Layer 3 PDU). The header contains information required to complete the transfer, such as source and destination logical addresses.



The data-link layer provides a service to the network layer by encapsulating the network layer packet in a frame (the Layer 2 PDU). The frame header contains the physical addresses required to complete the data-link functions, and the frame trailer contains the FCS.

The physical layer provides a service to the data-link layer, encoding the data-link frame into a pattern of 1s and 0s (bits) for transmission on the medium (usually a wire) at Layer 1.

Network devices such as hubs, switches, and routers work at the lower three layers. Hubs are at Layer 1 – the physical layer, switches are at Layer 2 – the data-link layer, and routers are at Layer 3 – the network layer.



Quiz

Match the communication process with its definition.

Options:

1. Encapsulation 2. De-encapsulation 3. Peer-to-peer communication

Targets:

a. This is the process that wraps data with the necessary protocol information before network transit. b. This is the process that checks for errors, and begins the process of stripping the header and trailer

from received data. c. This is the process that facilitates the communication between OSI peer layers during data transfer.

Answerxvi

(See Endnotes).

4. The TCP/IP protocol stack

Although the OSI reference model is universally recognized, the historical and technical open standard of the Internet is the TCP/IP protocol stack.

The TCP/IP protocol stack has four layers – the application layer, the transport layer, the Internet layer, and the network access layer. It is important to note that although some of the layers in the TCP/IP protocol stack have the same names as layers in the OSI model, the layers have different functions in each model.

The following are the TCP/IP protocol stack layers.

Application Transport Internet Network access



Application

The application layer handles high-level protocols, including issues of representation, encoding, and dialog control. The TCP/IP model combines all application-related issues into one layer and ensures that this data is properly packaged for the next layer.

Transport

The transport layer deals with quality-of-service issues of reliability, flow control, and error correction. One of its protocols, the Transmission Control Protocol (TCP), provides for reliable network communications.

Internet

The purpose of the Internet layer is to send source packets from any network on the internetwork and have them arrive at the destination, regardless of the path they took to get there.

Network access

The network access layer is also called the host-to-network layer. It includes the LAN and WAN protocols, and all the details in the OSI physical and data-link layers.

There are similarities and differences between the TCP/IP protocol stack and the OSI reference model.

The main similarities between the TCP/IP protocol stack and the OSI reference model are

application layers packet-switched technology transport and network layers

application layers

Both have application layers, though they include different services.

packet-switched technology

Both assume packet-switched technology, not circuit-switched. (Analog telephone calls are an example of circuit-switched.)

transport and network layers



Both have comparable transport and network layers.

The main differences between the TCP/IP protocol stack and the OSI reference model are

data-link and physical layers implementation of standards presentation and session layers

data-link and physical layers

TCP/IP combines the OSI data-link and physical layers into the network access layer.

implementation of standards

TCP/IP protocols are the standards around which the Internet developed, so the TCP/IP protocol stack gains credibility just because of the widespread implementation of its protocols. In contrast, networks are not typically built on the OSI model, even though the OSI model is used as a guide.

presentation and session layers

TCP/IP combines the OSI presentation and session layers into its application layer.

Quiz

In the TCP/IP protocol stack, which layer deals with reliability, flow control, and error correction?

Options:

1. Application 2. Internet 3. Network access 4. Transport

Answerxvii

(See Endnotes).

Summary

The advent of LANs, WANs, and MANs in the 1980s and 1990s was largely unregulated and no standard for network communication was available. As a result it became more difficult for networks using different specifications and implementations to communicate with each other. To resolve this, the ISO created and released the OSI reference model in 1984 to provide vendors with a set of standards to ensure greater compatibility and interoperability between various types of network technologies.

The OSI reference model comprises seven layers – the application, presentation, session, transport, network, data-link, and physical layer. Each layer has its own function. The application layer provides network services to the user applications. The presentation layer presents the data in a format that will be understood by the receiving application. The session layer regulates the session between the communicating hosts. The transport layer ensures reliable transport of the data. The network layer routes the packets through the network. The data-link layer controls access to the network. The physical layer sends the data along the physical wire.



Encapsulating wraps data with the necessary protocol information before sending it across the network. De-encapsulation strips the protocol information when the data is received. Each OSI layer at the source communicates with its peer layer at the destination – this is called peer-to-peer communication.

The TCP/IP protocol stack has four layers – the application layer, transport layer, internet layer, and network access layer. There are both similarities and differences between the TCP/IP protocol stack and the OSI reference model. The TCP/IP protocol stack is widely implemented whereas the OSI reference model is widely used for reference.



F. Working with the OSI model

After completing this topic, you should be able to distinguish between basic computer and networking terms, and between the principles of the OSI reference model and the TCP/IP protocol stack.

Exercise overview

Task1: Networking terms and functions

Task 2: Functions of the OSI model

Task 3: The data encapsulation process

Exercise overview

In this exercise, you are required to identify networking terms and functions, and the functions of the OSI reference model. You will also examine data communication methods.

This involves the following tasks:

identifying networking terms and functions defining the functions of each OSI layer examining the data encapsulation process

Task1: Networking terms and functions

The topology of a network describes the layout of the wire and devices as well as the paths used by data transmissions.

Match the schematic description with its function.

Options:

1. Logical topology 2. Physical topology

Targets:

a. This defines the structure of the paths that the signals take within a network b. This describes the physical layout or structure of the network

Result

The logical topology is the structure of the paths that the signals take within a network and the physical topology refers to the physical layout or structure of the network.



The logical topology defines the structure of the paths that the signals take within a network. Although the logical topology does not have to correspond to the physical topology, it is often the same as the physical topology.

The physical topology is the actual physical shape of the network. Networks can be arranged in a bus, star, ring, or mesh format.

Network applications are software programs that run between different computers connected on a network. Each application type has an associated protocol depending on the function of the application.

Step 2 of 3

Which application transfers files between remote computers?

Options:

1. FTP 2. HTTP 3. POP3 4. SMNP

Result

File transfer protocol (FTP) is used to transfer files between remote computers.

Option 1 is correct. FTP is a simple file utility program used for transferring files between remote computers.

Option 2 is incorrect. Hypertext Transfer Protocol (HTTP) establishes a connection between a browser and a web server allowing the client to view web pages in the web browser.

Option 3 is incorrect. When you send an email it is usually Post Office Protocol version 3 (POP3) that will hold the mail in a storage container until the receiver is ready to download it.

Option 4 is incorrect. Simple network monitoring protocol (SNMP) is used for monitoring network device status and activities.



A LAN covers a smaller geographic area than a MAN or a WAN.

Step 3 of 3

Home office users are most likely to connect to the main office LAN using what WAN technology?

Options:

1. Frame Relay 2. ADSL 3. Leased lines 4. X.25

Result

Home office users are most likely to connect to the main office LAN using an ADSL connection.

Option 1 is incorrect. Frame Relay provides a permanent serial connection. Due to the cost of such connections, this is not an effective solution for home office users

Option 2 is correct. An ADSL connection is a dial-up connection, and is often used by home office users to connect to a LAN.

Option 3 is incorrect. A WAN connection to the remote branch office requires a permanent connection such as a leased line. Home office users will most often use a dial-up technology.

Option 4 is incorrect. X.25 is an older form of permanent serial connection, not used very often in modern networks. Due to the cost of such connections, this is not an effective solution for home office users.

Task 2: Functions of the OSI model

The OSI reference model has seven layers, each illustrating a particular network function. This separation of networking functions is called layering.



1 of 1

What layer defines voltage levels, timing of voltage changes and maximum transmission distances?

Options:

1. The data-link layer 2. The network layer 3. The physical layer 4. The session layer 5. The transport layer

Result

The physical layer defines voltage levels, timing of voltage changes and maximum transmission distances.

Option 1 is incorrect. The data-link layer controls network access and formats data before it is transmitted to ensure that it will be properly received.

Option 2 is incorrect. The network layer provides connectivity and path selection for data when moving between different network locations.

Option 3 is correct. The physical layer defines the hardware specifications required for end-system communications.

Option 4 is incorrect. The session layer regulates the communication processes of conversations between hosts.

Option 5 is incorrect. The transport layer is responsible for the reliable transfer of data between network hosts.

Task 3: The data encapsulation process

Data packets are packaged in a process known as encapsulation before they travel safely across a network.



Step 1 of 1

Which of the following describes the first step of data encapsulation?

Options:

1. A data-link header is stripped from the message 2. The frame is converted into binary format 3. The data-link layer checks the data-link trailer to see if the data is in error 4. The user data is sent from an application to the application layer

Result

The first step of data encapsulation is when the user data is sent from an application to the application layer.

Option 1 is incorrect. This occurs during de-encapsulation. When a message arrives at the data-link layer, it is checked for errors. If no errors exist, it is then stripped of its data-link header and trailer, and passed on up to the network layer.

Option 2 is incorrect. Conversion to binary is one of the last processes that occurs before the data frame is transmitted onto the network media.

Option 3 is incorrect. The FCS trailer is checked after the data has been received from the network and has been passed from the physical layer to the data-link layer. This is actually a part of the de-encapsulation process.

Option 4 is correct. When data is sent from an application for transmission on the network, the encapsulation process begins. Encapsulation begins at the application layer and wraps data with the necessary protocol information before network transit.



G. Glossary

ABR Acronym for available bit rate. See UBR.

access list List kept by Cisco routers to control access to or from the router for a number of services (for example, to prevent packets with a certain IP address from leaving a particular interface on the router).

acknowledgment Notification sent from one network device to another to acknowledge that some event (for example, receipt of a message) has occurred. Sometimes abbreviated ACK.

active hub Multiport device that amplifies LAN transmission signals.

adapter An adapter is a physical device that allows one hardware or electronic interface to be adapted (accommodated without loss of function) to another hardware or electronic interface. In a computer, an adapter is often built into a card that can be inserted into a slot on the computer's motherboard. The card adapts information that is exchanged between the computer's microprocessor and the devices that the card supports.

adaptive routing See dynamic routing.

address Data structure or logical convention used to identify a unique entity, such as a particular process or network device.

Address Resolution Protocol Abbreviated to ARP.

administrative distance A rating of the trustworthiness of a routing information source. In Cisco routers, administrative distance is expressed as a numerical value between 0 and 255. The higher the value, the lower the trustworthiness rating.

ADSL Acronym for asymmetric digital subscriber line. One of four DSL technologies. ADSL is designed to deliver more bandwidth downstream (from the central office to the customer site) than upstream. Downstream rates range from 1.5 to 9 Mbps, while upstream bandwidth ranges from 16 to 640 kbps. ADSL transmissions work at distances up to 18,000 feet (5,488 meters) over a single copper twisted pair.

algorithm Well-defined rule or process for arriving at a solution to a problem. In networking, algorithms are commonly used to determine the best route for traffic from a particular source to a particular destination.

American National Standards Institute See ANSI.

American Standard Code for Information Interchange See ASCII

ANSI Acronym for American National Standards Institute. Voluntary organization comprised of corporate, government, and other members that coordinates standards-related activities, approves U.S. national standards, and develops positions for the United States in international standards organizations. ANSI helps develop international and U.S. standards relating to, among other things, communications and networking. ANSI is a member of the IEC and the ISO.

API



Acronym for application programming interface. Specification of function-call conventions that defines an interface to a service.

application layer Layer 7 of the OSI reference model. This layer provides services to application processes (such as electronic mail, file transfer, and terminal emulation) that are outside of the OSI model. The application layer identifies and establishes the availability of intended communication partners (and the resources required to connect with them), synchronizes cooperating applications, and establishes agreement on procedures for error recovery and control of data integrity. Corresponds roughly with the transaction services layer in the SNA model.

application programming interface See API.

ARP Acronym for Address Resolution Protocol. Internet protocol used to map an IP address to a MAC address. Defined in RFC 826. Compare with RARP.

ASCII Acronym for American Standard Code for Information Interchange. 8-bit code for character representation (7 bits plus parity).

asymmetric digital subscriber line Abbreviated to ADSL.

asynchronous timedivision multiplexing See ATDM

Asynchronous Transfer Mode See ATM.

asynchronous transmission Term describing digital signals that are transmitted without precise clocking. Such signals generally have different frequencies and phase relationships. Asynchronous transmissions usually encapsulate individual characters in control bits (called start and stop bits) that designate the beginning and end of each character.

ATDM Acronym for asynchronous time-division multiplexing. Method of sending information that resembles normal TDM, except that time slots are allocated as needed rather than preassigned to specific transmitters. See FDM.

ATM Acronym for Asynchronous Transfer Mode. International standard for cell relay in which multiple service types (such as voice, video, or data) are conveyed in fixed-length (53-byte) cells. Fixed-length cells allow cell processing to occur in hardware, thereby reducing transit delays. ATM is designed to take advantage of high-speed transmission media such as E3, SONET, and T3.

attachment unit interface See AUI.

attenuation Loss of communication signal energy.

attribute Configuration data that defines the characteristics of database objects such as the chassis, cards, ports, or virtual circuits of a particular device. Attributes might be preset or user-configurable.

AUI Attachment unit interface. IEEE 802.3 interface between an MAU and a NIC (network interface card). The term AUI can also refer to the rear panel port to which an AUI cable might attach, such as those found on a Cisco LightStream Ethernet access card. Also called transceiver cable.

autonomous system

https://elms.faa.gov/skillsoft/cbtlib/219381/eng/references/glossary.html#OSI

https://elms.faa.gov/skillsoft/cbtlib/219381/eng/references/glossary.html#RARP



Collection of networks under a common administration sharing a common routing strategy. Autonomous systems are subdivided by areas. An autonomous system must be assigned a unique 16-bit number by the IANA. Sometimes abbreviated AS.

back end Node or software program that provides services to a front end. Usually transparent to the user.

backbone The part of a network that acts as the primary path for traffic that is most often sourced from, and destined for, other networks.

backbone cabling Cabling that provides interconnections between wiring closets, wiring closets and the POP, and between buildings that are part of the same LAN. Also known as vertical cabling.

backplane The backplane is a large circuit board that contains sockets for expansion cards.

backward explicit congestion notification See BECN.

bandwidth The difference between the highest and lowest frequencies available for network signals. The term is also used to describe the rated throughput capacity of a given network medium or protocol.

baseband Characteristic of a network technology where only one carrier frequency is used. Ethernet is an example of a baseband network. Also called narrowband.

Basic Rate Interface See BRI.

baud Unit of signaling speed equal to the number of discrete signal elements transmitted per second. Baud is synonymous with bits per second (bps), if each signal element represents exactly 1 bit.

B-channel The name for a bearer channel. DS0 time slot that carries analog voice or digital data over ISDN. In ISDN, a full-duplex, 64-kbps channel used to send user data.

BECN Acronym for backward explicit congestion notification. Bit set by a Frame Relay network in frames traveling in the opposite direction of frames encountering a congested path. DTE receiving frames with the BECN bit set can request that higher-level protocols take flow control action as appropriate. Compare with FECN.

BGP Acronym for Border Gateway Protocol. Interdomain routing protocol that replaces EGP. BGP exchanges reachability information with other BGP systems. It is defined by RFC 1163.

BGP4 BGP Version 4. Version 4 of the predominant interdomain routing protocol used on the Internet. BGP4 supports CIDR and uses route aggregation mechanisms to reduce the size of routing tables.

Bit The smallest unit of data in a computer. A bit equals 1 or 0, and is the binary format in which data is processed by computers.

Border Gateway Protocol See BGP.

BPDU Acronym for bridge protocol data unit. Spanning-Tree Protocol hello packet that is sent out at configurable intervals to exchange information among bridges in the network.

BRI Acronym for Basic Rate Interface. ISDN interface composed of two B channels and one D channel for circuit-switched communication of voice, video, and data.



bridge Device that connects and passes packets between two network segments that use the same communications protocol. Bridges operate at the data-link layer (Layer 2) of the OSI reference model. In general, a bridge will filter, forward, or flood an incoming frame based on the MAC address of that frame.

bridge protocol data unit See BPDU.

broadband Transmission system that multiplexes multiple independent signals onto one cable. In telecommunications terminology, any channel having a bandwidth greater than a voicegrade channel (4 kHz). In LAN terminology, a coaxial cable on which analog signaling is used. Also called wideband.

broadcast Data packet that will be sent to all nodes on a network. Broadcasts are identified by a broadcast address. Compare with multicast and unicast.

broadcast address Special address reserved for sending a message to all stations. Generally, a broadcast address is a MAC destination address of all ones.

broadcast domain The set of all devices that will receive broadcast frames originating from any device within the set. Broadcast domains are typically bounded by routers because routers do not forward broadcast frames.

broadcast storm Undesirable network event in which many broadcasts are sent simultaneously across all network segments. A broadcast storm uses substantial network bandwidth and, typically, causes network time-outs.

buffer Storage area used for handling data in transit. Buffers are used in internetworking to compensate for differences in processing speed between network devices. Bursts of data can be stored in buffers until they can be handled by slower processing devices. Sometimes referred to as a packet buffer.

bus A bus is a collection of wires through which data is transmitted from one part of a computer to another. The bus connects all the internal computer components to the CPU. The ISA and the PCI are two types of buses.

bus topology Linear LAN architecture in which transmissions from network stations propagate the length of the medium and are received by all other stations.

byte A byte is a unit of measure used to describe the size of a data file, the amount of space on a disk or other storage medium, or the amount of data being sent over a network. One byte equals eight bits of data.

cable Transmission medium of copper wire or optical fiber wrapped in a protective cover.

Canadian Standards Association See CSA.

carrier sense multiple access collision detect See CSMA/CD.

catchment area Zone that falls within area that can be served by an internetworking device such as a hub.

Category 1 cabling



One of five grades of UTP cabling described in the EIA/TIA-568B standard. Category 1 cabling is used for telephone communications and is not suitable for transmitting data. Compare with Category 2 cabling, Category 3 cabling, Category 4 cabling, and Category 5 cabling.

Category 2 cabling One of five grades of UTP cabling described in the EIA/TIA-568B standard. Category 2 cabling is capable of transmitting data at speeds up to 4 Mbps. Compare with Category 1 cabling, Category 3 cabling, Category 4 cabling, and Category 5 cabling.

Category 3 cabling One of five grades of UTP cabling described in the EIA/TIA-568B standard. Category 3 cabling is used in 10BASE-T networks and can transmit data at speeds up to 10 Mbps. Compare with Category 1 cabling, Category 2 cabling, Category 4 cabling, and Category 5 cabling.

Category 4 cabling One of five grades of UTP cabling described in the EIA/TIA-568B standard. Category 4 cabling is used in Token Ring networks and can transmit data at speeds up to 16 Mbps. Compare with Category 1 cabling, Category 2 cabling, Category 3 cabling, and Category 5 cabling.

Category 5 cabling One of five grades of UTP cabling described in the EIA/TIA-568B standard. Category 5 cabling is used for running CDDI and can transmit data at speeds up to 100 Mbps. Compare with Category 1 cabling, Category 2 cabling, Category 3 cabling, and Category 4 cabling.

CDDI Acronym for Copper Distributed Data Interface. Implementation of FDDI protocols over STP and UTP cabling. CDDI transmits over relatively short distances (about 100 meters), providing data rates of 100 Mbps using a dual-ring architecture to provide redundancy. Based on the ANSI Twisted-Pair Physical Medium Dependent (TPPMD) standard. See FDDI.

CDP Acronym for Cisco Discovery Protocol. Media- and protocol-independent device-discovery protocol that runs on all Cisco-manufactured equipment by default including routers, access servers, bridges, and switches. Using CDP, a device can advertise its existence to other devices and receive information about other devices on the same LAN or on the remote side of a WAN. Runs on all media that support SNAP, including LANs, Frame Relay, and ATM media. CDP is a Layer 2 multicast technology.

cell The basic unit for ATM switching and multiplexing. Cells contain identifiers that specify the data stream to which they belong. Each cell consists of a 5-byte header and 48 bytes of payload.

cell switching Network technology based on the use of small, fixed-size packets, or cells. Because cells are fixed-length, they can be processed and switched in hardware at high speeds. Cell relay is the basis for many high-speed network protocols including ATM, IEEE 802.6, and SMDS.

Challenge Handshake Authentication Protocol See CHAP.

channel service unit See CSU.

channelized T1 Access link operating at 1.544 Mbps that is subdivided into 24 channels (23 B-channels and 1 D-channel) of 64 Kbps each. The individual channels or groups of channels connect to different destinations. Supports DDR, Frame Relay, and X.25. Also referred to as fractional T1.

CHAP Acronym for Challenge Handshake Authentication Protocol. Security feature supported on lines using PPP encapsulation that prevents unauthorized access. CHAP does not itself prevent unauthorized access, it merely identifies the remote end. The router or access server then determines whether that user is allowed access.



checksum Method for checking the integrity of transmitted data. A checksum is an integer value computed from a sequence of octets taken through a series of arithmetic operations. The value is recomputed at the receiving end and compared for verification.

CIR Acronym for committed information rate. The rate at which a Frame Relay network agrees to transfer information under normal conditions, averaged over a minimum increment of time. CIR, measured in bits per second, is one of the key negotiated tariff metrics.

circuit switching Switching system in which a dedicated physical circuit path must exist between sender and receiver for the duration of the call. Used heavily in the telephone company network. Circuit switching can be contrasted with contention and token passing as a channelaccess method, and with message switching and packet switching as a switching technique.

Cisco Discovery Protocol See CDP.

classful network Network that uses traditional IP network addresses of class A, class B, and class C. The network boundary is defined by using a prefix value that indicates the number of bits used for the network portion.

classless network Network that does not use the traditional IP network addressing (class A, class B, and class C). The network boundary is defined by the use of a network mask or subnet mask and a logical "AND" operation between the subnet mask and IP address. Classless networks are more pervasive in today's networks because of flexibility and less wasted IP addresses.

CLI Acronym for Command Language Interpreter. The basic Cisco IOS configuration and management interface.

client Node or software program (front-end device) that requests services from a server.

client-server model Common way to describe network services and the model user processes (programs) of those services. Examples include the nameserver/nameresolver paradigm of the DNS and fileserver/file-client relationships such as NFS and diskless hosts.

CN Acronym for Content Network. A collection of devices that optimizes the delivery of Internet content (such as HTML documents and MPEG files) by caching content near clients, by proactively pushing content into those caches, and by routing each client request to the best device available at that moment to serve the particular content requested.

coaxial cable Cable consisting of a hollow outer cylindrical conductor that surrounds a single inner wire conductor. Two types of coaxial cable are currently used in LANs: 50-ohm cable, which is used for digital signaling, and 75-ohm cable, which is used for analog signal and highspeed digital signaling.

collapsed backbone Nondistributed backbone in which all network segments are interconnected by way of an internetworking device. A collapsed backbone might be a virtual network segment existing in a device such as a hub, a router, or a switch.

collision In Ethernet, the result of two nodes transmitting simultaneously. The frames from each device impact and are damaged when they meet on the physical media.

Command Language Interpreter See CLI



committed information rate See CIR.

communication Transmission of information.

compression The running of a data set through an algorithm that reduces the space required to store or the bandwidth required to transmit the data set.

computer A device that computes. More recently, a device that can solve billions of equations per second.

concentrator Any device that enables multiple physical or logical connections to be made at or to a single point. A hub is an example of a device that allows multiple physical connections into that single hub.

conductor Any material with a low resistance to electrical current. Any material capable of carrying an electrical current.

configuration register In Cisco devices, a 16-bit, user-configurable value that determines how the router functions during initialization. The configuration register can be stored in hardware or software. In hardware, the bit position is set using a jumper. In software, the bit position is set by specifying a hexadecimal value using configuration commands.

congestion Traffic in excess of network capacity.

connectionless Term used to describe data transfer without the existence of a virtual circuit, error detection, and acknowledgments.

connection-oriented Term used to describe data transfer with the existence of a virtual circuit, error detection, and acknowledgments.

console DTE through which commands are entered into a host. The functionality can be provided for through a terminal device or application such as Telnet.

Content Network See CN.

contention Network media access method in which network devices compete for permission to access the physical medium.

convergence The speed and ability of a group of internetworking devices running a specific routing protocol or Spanning-Tree Protocol to agree on the topology of an internetwork after a change in that topology.

Copper Distributed Data Interface See CDDI.

cost Arbitrary value, typically based on hop count, media bandwidth, or other measures, that is assigned by a network administrator and used to compare various paths through an internetwork environment. Cost values are used by Layer 2 and Layer 3 protocols, such as STP and routing protocols respectively, to determine the most favorable path to a particular destination: the lower the cost, the better the path. Sometimes called path cost.

cps Acronym for cells per second.

CPU



Acronym for central processing unit. The CPU is the "brains" of the computer, where most of the calculations and processing take place.

CRC Acronym for cyclic redundancy check. Error-checking technique in which the frame recipient calculates a remainder by dividing frame contents by a prime binary divisor and compares the calculated remainder to a value stored in the frame by the sending node.

CSA Acronym for Canadian Standards Association. Agency within Canada that certifies products that conform to Canadian national safety standards.

CSMA/CD Acronym for Carrier sense multiple access collision detect. Contention based Media-access mechanism wherein devices ready to transmit data first check the channel for a carrier. If no carrier is sensed for a specific period of time, a device can transmit. If two devices transmit at once, a collision occurs and is detected by all colliding devices. This collision subsequently delays retransmissions from those devices for some random length of time. CSMA/CD access is used by Ethernet and IEEE 802.3.

CSU Acronym for channel service unit. Digital interface device that connects end-user equipment to the local digital telephone loop. Often referred to together with DSU, as CSU/DSU.

cyclic redundancy check See CRC.

data circuit-terminating equipment See DCE.

data communications equipment See DCE

Data Encryption Standard See DES.

data service unit See DSU.

data terminal equipment See DTE.

data-link layer Layer 2 of the OSI reference model. This layer provides reliable transit of data across a physical link. The data-link layer is concerned with physical addressing, network topology, line discipline, error notification, ordered delivery of frames, and flow control. The IEEE has divided this layer into two sublayers: the MAC sublayer and the LLC sublayer. Sometimes simply called link layer. Roughly corresponds to the data-link control layer of the SNA model.

DCE Data communications equipment (EIA expansion) or data circuit-terminating equipment (ITU-T expansion). The devices and connections of a communications network that comprise the network end of the user-to-network interface. The DCE provides a physical connection to the network, forwards traffic, and provides a clocking signal used to synchronize data transmission between DCE and DTE devices. Switches, modems and interface cards are examples of DCE.

D-channel (data channel) Full-duplex, 16-kbps (BRI), or 64-kbps (PRI) ISDN channel used for call setup (BRI), control, and protocol negotiations.

DDR Acronym for Dial-on-demand routing. Technique whereby a Cisco router can automatically initiate and close a circuit-switched session as transmitting stations demand. The router spoofs keepalives so that end stations treat the session as active. DDR permits routing over ISDN or telephone lines using an external ISDN terminal adaptor or modem.



DECnet Group of communications products (including a protocol suite) developed and supported by Digital Equipment Corporation. DECnet/OSI (also called DECnet Phase V) is the most recent iteration and supports both OSI protocols and proprietary digital protocols. Phase IV Prime supports inherent MAC addresses that allow DECnet nodes to coexist with systems running other protocols that have MAC address restrictions.

decryption The reverse application of an encryption algorithm to encrypted data, thereby restoring that data to its original, unencrypted state.

default route Routing table entry that is used to direct frames for which a next hop is not explicitly listed in the routing table.

demarc Demarcation point between carrier equipment and CPE. The point at which the service provider's local loop ends and the customer's network begins.

demodulation Process of returning a modulated signal to its original form. Modems perform demodulation by taking an analog signal and returning it to its original (digital) form.

demultiplexing The separating of multiple input streams that have been multiplexed into a common physical signal back into multiple output streams.

DES Acronym for Data Encryption Standard. Standard cryptographic algorithm developed by the U.S. NBS.

dial-on-demand routing See DDR.

DNS Acronym for Domain Naming System. System used in the Internet for translating names of network nodes into IP addresses.

domain In the Internet, a portion of the naming hierarchy tree that refers to general groupings of networks based on organization-type or geography. Also can be generally used to describe a logical grouping of networked devices that exhibit the same characteristics or use the same protocols.

dot address Refers to the common notation for IP addresses in the form <a.b.c.d> where each number represents, in decimal, 1 byte of the 4-byte IP address. Also called dotted notation or four-part dotted notation.

dotted decimal notation Syntactic representation for a 32-bit integer that consists of four 8-bit numbers written in base 10 with periods (dots) separating them. Used to represent IP addresses.

DRAM Acronym for dynamic random-access memory. RAM that stores information in capacitors that must be periodically refreshed. DRAMs are less complex and have greater capacity than SRAMs.

DS0 Digital signal level 0. Framing specification used in transmitting digital signals over a single channel at 64 kbps on an ISDN facility.

DS1 Digital signal level 1. Framing specification used in transmitting digital signals at 1.544 Mbps on a T1 facility (in the U.S.) or at 2.048-Mbps on an E1 facility (in Europe).

DS3



Digital signal level 3. Framing specification used for transmitting digital signals at 44.736 Mbps on a T3 facility and 34.368 on an E3 facility.

DSU Acronym for data service unit. Device used in digital transmission that adapts the physical interface on a DTE device to a transmission facility such as T1 or E1. The DSU is also responsible for such functions as signal timing. Often referred to together with CSU, as CSU/DSU.

DTE Acronym for data terminal equipment. Device at the user end of a user-network interface that serves as a data source, destination, or both. DTE connects to a data network through a DCE device (for example, a modem) and typically uses clocking signals generated by the DCE. DTE includes such devices as computers, routers, protocol translators, and multiplexers.

dynamic random-access memory See DRAM.

dynamic routing Routing that adjusts automatically to network topology or traffic changes. Also called adaptive routing. Requires that a routing protocol be run between routers.

E1 Wide-area digital transmission scheme used predominantly in Europe that carries data at a rate of 2.048 Mbps. E1 lines can be leased for private use from common carriers.

E3 Wide-area digital transmission scheme used predominantly in Europe that carries data at a rate of 34.368 Mbps. E3 lines can be leased for private use from common carriers.

EBCDIC Acronym for extended binary coded decimal interchange code. Any of a number of coded character sets developed by IBM consisting of 8-bit coded characters. This character code is used by older IBM systems and telex machines.

EEPROM Acronym for Electrically Erasable Programmable Read-Only Memory. EPROM that can be erased using electrical signals applied to specific pins.

EGP Acronym for Exterior Gateway Protocol. Internet protocol for exchanging routing information between autonomous systems. Documented in RFC 904. Not to be confused with the general term exterior gateway protocol. EGP is an obsolete protocol that has been replaced by BGP.

EIA/TIA-232 Common physical-layer interface standard, developed by EIA and TIA, that supports unbalanced circuits at signal speeds of up to 64 kbps. Closely resembles the V.24 specification. Formerly known as RS-232.

EIA/TIA-449 Popular physical-layer interface developed by EIA and TIA. Essentially, a faster (up to 2 Mbps) version of EIA/TIA-232 capable of longer cable runs. Formerly called RS-449.

EIA/TIA-568 Standard that describes the characteristics and applications for various grades of UTP cabling.

EIA/TIA-606 Administration standard for the telecommunications infrastructure of commercial buildings. It includes the following administration areas: terminations, media, pathways, spaces, bounding, and grounding.

EIA-530 Refers to two electrical implementations of EIA/TIA-449: RS-422 (for balanced transmission) and RS-423 (for unbalanced transmission).

EIGRP



Acronym for Enhanced Interior Gateway Routing Protocol. Advanced version of IGRP developed by Cisco. Provides superior convergence properties and operating efficiency, and combines the advantages of link state protocols with those of distance vector protocols.

EISA Acronym for Extended Industry-Standard Architecture. 32-bit bus interface used in PCs, PC-based servers, and some UNIX workstations and servers.

Electrically Erasable Programmable Read-Only Memory See EEPROM

electromagnetic interference See EMI.

electromagnetic pulse See EMP.

electrostatic discharge See ESD.

EMI Acronym for electromagnetic interference. Interference by electromagnetic signals that can cause reduced data integrity and increased error rates on transmission channels.

EMP Acronym for electromagnetic pulse. Caused by lightning and other high-energy phenomena. Capable of coupling enough energy into unshielded conductors to destroy electronic devices.

encapsulation Device or software that modifies information into the required transmission format.

encoding Process by which bits are represented by voltages.

encryption The application of a specific algorithm to data so as to alter the appearance of the data making it incomprehensible to those who are not authorized to see the information.

end of transmission See EOT.

Enhanced Interior Gateway Routing Protocol See EIGRP.

enterprise network Large and diverse network connecting most major points in a company or other organization. Differs from a WAN in that it is privately owned and maintained.

EOT Acronym for end of transmission. Generally, a character that signifies the end of a logical group of characters or bits.

EPROM Acronym for erasable programmable read-only memory. Nonvolatile memory chips that are programmed after they are manufactured, and, if necessary, can be erased by some means and reprogrammed. Compare with EEPROM and PROM.

erasable programmable read-only memory See EPROM.

ESD Acronym for electrostatic discharge. A flow or spark of electricity that originates from a static source such as a carpet and arcs across a gap to another object.

Ethernet Baseband LAN specification invented by Xerox Corporation and developed jointly by Xerox, Intel, and Digital Equipment Corporation. Ethernet networks use CSMA/CD and run over a variety of cable types at 10 Mbps. Ethernet is similar to the IEEE 802.3 series of standards.

expansion card



The expansion card is a printed circuit board that can be inserted into a computer to give the computer added capabilities.

expansion slot The expansion slot is an opening in a computer where a circuit board can be inserted to add new capabilities to the computer.

extended binary coded decimal interchange code See EBCDIC.

Extended Industry- Standard Architecture See EISA.

Exterior Gateway Protocol See EGP.

Fast Ethernet Any of a number of 100-Mbps Ethernet specifications. Fast Ethernet offers a speed increase ten times that of the 10BASE-T Ethernet specification while preserving such qualities as frame format, MAC mechanisms, and MTU. Such similarities allow the use of existing 10BASE-T applications and network management tools on Fast Ethernet networks. Based on an extension to the IEEE 802.3 specification.

fast switching Cisco feature whereby a route cache is used to expedite packet switching through a router. Contrast with slow switching.

FCS Acronym for frame check sequence. Refers to the extra characters added to a frame for error control purposes. Used in HDLC, Frame Relay, and other data-link layer protocols.

FDDI Acronym for Fiber Distributed Data Interface. LAN standard, defined by ANSI X3T9.5, specifying a 100-Mbps token-passing network using fiber-optic cable, with transmission distances of up to 2 km. FDDI uses a dual-ring architecture to provide redundancy. Compare with CDDI and FDDI II.

FDDI II ANSI standard that enhances FDDI. FDDI II provides isochronous transmission for connectionless data circuits and connection-oriented voice and video circuits. Compare with FDDI.

FDM Acronym for frequency-division multiplexing. Technique whereby information from multiple channels can be allocated bandwidth on a single wire based on frequency. Compare with ATDM, statistical multiplexing, and TDM.

FECN Acronym for forward explicit congestion notification. Bit set by a Frame Relay network to inform DTE receiving the frame that congestion was experienced in the path from source to destination. DTE receiving frames with the FECN bit set can request that higher-level protocols take flow-control action as appropriate. Compare with BECN.

Fiber Distributed Data Interface See FDDI.

fiber-optic cable Physical medium capable of conducting modulated light transmission. Compared with other transmission media, fiber-optic cable is more expensive, but is not susceptible to electromagnetic interference, and is capable of higher data rates. Sometimes called optical fiber.

field-replaceable unit See FRU.

File Transfer Protocol See FTP.

firewall



Router or access server, or several routers or access servers, designated as a buffer between any connected public networks and a private network. A firewall router uses access lists and other methods to ensure the security of the private network.

firmware Software instructions set permanently or semi permanently in ROM.

flash memory Technology developed by Intel and licensed to other semiconductor companies. Flash memory is nonvolatile storage that can be electrically erased and reprogrammed. Allows software images to be stored, booted, and rewritten as necessary.

flash update Routing update sent asynchronously in response to a change in the network topology. Compare with routing update.

flat addressing Scheme of addressing that does not use a logical hierarchy to determine location.

flooding Traffic passing technique used by networking devices such as routers and switches in which traffic received on an interface is sent out all of the interfaces of that device except the interface on which the information was originally received.

flow Stream of data traveling between two endpoints across a network (for example, from one LAN station to another). Multiple flows can be transmitted on a single circuit.

flow control Technique for ensuring that a transmitting entity, such as a modem, does not overwhelm a receiving entity with data. When the buffers on the receiving device are full, a message is sent to the sending device to suspend the transmission until the data in the buffers has been processed. In IBM networks, this technique is called pacing.

forward explicit congestion notification See FECN.

fractional T1 Access link operating at 1.544 Mbps that is subdivided into 24 channels (23 B-channels and one D-channel) of 64 Kbps each. The individual channels or groups of channels connect to different destinations. Supports DDR, Frame Relay, and X.25. Also referred to as channelized T1.

fragment Piece of a larger packet that has been broken down to smaller units.

frame Logical grouping of information sent as a data-link layer unit over a transmission medium. Often refers to the header and trailer, used for synchronization and error control, that surround the user data contained in the unit. The terms datagram, message, packet, and segment are also used to describe logical information groupings at various layers of the OSI reference model and in various technology circles.

frame check sequence See FCS.

Frame Relay Industry-standard, switched data-link layer protocol that handles multiple virtual circuits using HDLC encapsulation between connected devices. Frame Relay is more efficient than X.25, the protocol for which it is generally considered a replacement.

frequency Number of cycles, measured in hertz, of an alternating current signal per unit time.

frequency-division multiplexing See FDM.

front end



Node or software program that requests services of a back end. Usually is the user interface. FRU

Acronym for field-replaceable unit. Hardware component that can be removed and replaced by Ciscocertified service providers. Typical FRUs include cards, power supplies, and chassis components.

FTP Acronym for File Transfer Protocol. Popular network application that allows files to be moved from one network device to another. Part of the TCP/IP protocol stack, used for transferring files between network nodes. FTP is defined in RFC 959.

full duplex Capability for simultaneous data transmission between a sending station and a receiving station.

full mesh Term describing a network in which devices are organized in a mesh topology, with each network node having either a physical circuit or a virtual circuit connecting it to every other network node. A full mesh provides a great deal of redundancy, but because it can be prohibitively expensive to implement, it is usually reserved for network backbones.

gateway In the IP community, an older term referring to a routing device. Today, the term router is used to describe nodes that perform this function, and gateway refers to a specialpurpose device that performs an application layer conversion of information from one protocol stack to another. Compare with router.

GB Acronym for gigabyte.

Gb Acronym for gigabit.

GBps Acronym for gigabytes per second.

Gbps Acronym for gigabits per second.

GHz Acronym for gigahertz

gigabit Abbreviated to Gb.

Gigabit Ethernet An extension of the IEEE 802.3 Ethernet standard, Gigabit Ethernet increases speed tenfold over Fast Ethernet, to 1000 Mbps, or 1 gigabit per second (Gbps). Two IEEE 802.3 standards, IEEE 802.3z and IEEE 802.3ab, define Gigabit Ethernet operations over fiber-optic and twisted-pair cable.

gigabits per second Abbreviated to Gbps.

gigabyte Abbreviated to GB.

gigabytes per second Abbreviated to GBps.

gigahertz Abbreviated to GHz.

gigahertz (GHz) A gigahertz is one thousand million, or 1 billion (1,000,000,000), cycles per second.

graphical user interface See GUI.

GUI( Acronym for graphical user interface. User environment that uses pictorial as well as textual representations of the input and output of applications and the hierarchical or other data structure



in which information is stored. Conventions such as buttons, icons, and windows are typical, and many actions are performed using a pointing device (such as a mouse). Microsoft Windows and the Apple Macintosh are prominent examples of platforms utilizing a GUI.

half duplex Capability for data transmission in only one direction at a time between a sending station and a receiving station. Compare with full duplex and simplex.

handshake Sequence of messages exchanged between two or more network devices to ensure transmission synchronization.

hard disk drive A drive device that reads and writes data on a hard disk, and is completely and internally self-contained. A hard drive allows for larger data storage capacity than floppy drives, and is non-removable.

hardware address MAC address.

HDLC Acronym for high-level data link control. Bit-oriented synchronous data-link layer protocol developed by ISO. Derived from SDLC, HDLC specifies a data encapsulation method on synchronous serial links using frame characters and checksums.

hertz (Hz) A hertz is a unit of frequency. It is the rate of change in the state or cycle in a sound wave, alternating current, or other cyclical waveform. It represents one cycle per second and is used to describe the speed of a computer microprocessor.

hexadecimal Base 16. A number representation using the digits 0 through 9, with their usual meaning, plus the letters A through F to represent hexadecimal digits with values of 10 to 15. The right-most digit counts ones, the next counts multiples of 16, then 16^2=256, etc.

hierarchical routing Routing based on a hierarchical addressing system. For example, IP routing algorithms use IP addresses, which contain network numbers, subnet numbers, and host numbers.

hierarchical star topology Extended star topology where a central hub is connected by vertical cabling to other hubs that are dependent on it.

high-level data link control See HDLC.

holddown State into which a route is placed so that routers will neither advertise the route nor accept advertisements about the route for a specific length of time (the holddown period). Holddown is used to flush bad information about a route from all routers in the network. A route is typically placed in holddown when a link in that route fails.

hop Term describing the passage of a data packet between two network nodes (for example, between two routers).

hop count Routing metric used to measure the distance between a source and a destination. RIP uses hop count as its sole metric.

host Computer system on a network. Similar to the term node except that host usually implies a computer system, whereas node generally applies to any networked system, including access servers and routers.

HTTP

https://elms.faa.gov/skillsoft/cbtlib/219381/eng/references/glossary.html#fullnduplex



Acronym for Hypertext Transfer Protocol. The protocol used by Web browsers and Web servers to transfer files, such as text and graphics files.

hub Generally, a term used to describe a device that serves as the center of a startopology network. 2. Hardware or software device that contains multiple independent but connected modules of network and internetwork equipment. Hubs can be active (where they repeat signals sent through them) or passive (where they do not repeat, but merely split, signals sent through them). 3. In Ethernet and IEEE 802.3, an Ethernet multiport repeater, sometimes referred to as a concentrator.

hypertext Electronically-stored text that allows direct access to other texts by way of encoded links. Hypertext documents can be created using HTML, and often integrate images, sound, and other media that are commonly viewed using a WWW browser.

Hypertext Transfer Protocol See HTTP.

Hz See hertz.

ICMP Acronym for Internet Control Message Protocol. Network layer Internet protocol that reports errors and provides other information relevant to IP packet processing. Documented in RFC 792.

IDF Acronym for Intermediate distribution facility. Secondary communications room for a building using a star networking topology. The IDF is dependent on the MDF.

IEEE 802.2 An IEEE LAN protocol that specifies an implementation of the LLC sublayer of the datalink layer. IEEE 802.2 handles errors, framing, flow control, and the network-layer (Layer 3) service interface. Used in IEEE 802.3 and IEEE 802.5 LANs.

IEEE 802.3 An IEEE LAN protocol that specifies an implementation of the physical layer and the MAC sublayer of the data-link layer. IEEE 802.3 uses CSMA/CD access at a variety of speeds over a variety of physical media. Extensions to the IEEE 802.3 standard specify implementations for Fast Ethernet. Physical variations of the original IEEE 802.3 specification include 10BASE2, 10BASE5, 10BASE-F, 10BASE-T, and 10Broad36. Physical variations for Fast Ethernet include 100BASE-TX and 100BASE-FX.

IGP Acronym for Interior Gateway Protocol. Internet protocol used to exchange routing information within an autonomous system. Examples of common Internet IGPs include IGRP, OSPF, and RIP.

IGRP Acronym for Interior Gateway Routing Protocol. IGP developed by Cisco to address the problems associated with routing in large, heterogeneous networks. Compare with Enhanced IGRP.

in-band signaling Transmission within a frequency range normally used for information transmission. Compare with out-of-band signaling.

Industry Standard Architecture See ISA.

infrared Electromagnetic waves whose frequency range is above that of microwaves, but below that of the visible spectrum. LAN systems based on this technology represent an emerging technology.

insulator Any material with a high resistance to electrical current.

Integrated Services Digital Network See ISDN.

Interface



1.Connection between two systems or devices. <br /> 2. In routing terminology, a network connection. <br /> 4. The boundary between adjacent layers of the <a href="#"><span class="crossref">OSI</span></a>model.

Interior Gateway Protocol See IGP.

Interior Gateway Routing Protocol See IGRP.

Intermediate distribution facility See IDF.

Intermediate System-to-Intermediate System See IS-IS.

internet Short for internetwork. Not to be confused with the Internet.

Internet Term used to refer to the largest global internetwork, connecting tens of thousands of networks worldwide and having a "culture" that focuses on research and standardization based on real-life use. Many leading-edge network technologies come from the Internet community. The Internet evolved in part from ARPANET. At one time, called the DARPA Internet. Not to be confused with the general term internet.

Internet Control Message Protocol See ICMP.

internetwork Collection of networks interconnected by routers and other devices that functions (generally) as a single network. Sometimes called an internet, which is not to be confused with the Internet.

Internetwork Packet Exchange See IPX.

internetworking General term used to refer to the industry that has arisen around the problem of connecting networks together. The term can refer to products, procedures, and technologies.

IPX Acronym for Internetwork Packet Exchange. NetWare network layer (Layer 3) protocol used for transferring data from servers to workstations. IPX is similar to IP and XNS.

ISA Acronym for Industry Standard Architecture. An older standard for connecting peripherals to a personal computer. Used primarily in AT-style IBM compatibles.

ISDN Acronym for Integrated Services Digital Network. Communication protocol, offered by telephone companies, that permits telephone networks to carry data, voice, and other source traffic.

IS-IS Acronym for Intermediate System-to-Intermediate System. OSI link-state hierarchical routing protocol based on DECnet Phase V routing whereby ISs (routers) exchange routing information based on a single metric to determine network topology. Compare with Integrated IS-IS.

jabber Error condition in which a network device continually transmits random, meaningless data onto the network. 2. In IEEE 802.3, a data packet whose length exceeds that prescribed in the standard.

jitter Analog communication line distortion caused by the variation of a signal from its reference timing positions. Jitter can cause data loss, particularly at high speeds.

jumper



Term used for patchcords found in a wiring closet. 2.)Electrical switch consisting of a number of pins and a connector that can be attached to the pins in a variety of different ways. Different circuits are created by attaching the connector to different pins.

KB Acronym for kilobyte. Approximately 1000 bytes.

Kb Acronym for kilobit. Approximately 1000 bits.

kBps Acronym for kilobytes per second.

kbps Acronym for kilobits per second.

keepalive interval Period of time between each keepalive message sent by a network device.

keepalive message Message sent by one network device to inform another network device that the virtual circuit between the two is still active.

kilobit Abbreviated to kb.

kilobits per second Abbreviated to kbps. This is a standard measurement of the amount of data transferred over a network connection.

kilobyte Abbreviated to KB.

kilobytes per second Abbreviated to kBps. This is a standard measurement of the amount of data transferred over a network connection.

LAN Acronym for local-area network. High-speed, low-error data network covering a relatively small geographic area (up to a few thousand meters). LANs connect workstations, peripherals, terminals, and other devices in a single building or other geographically limited area. LAN standards specify cabling and signaling at the physical and data-link layers of the OSI model. Ethernet, FDDI, and Token Ring are widely used LAN technologies.

LAN switch High-speed switch that forwards packets between data-link segments. Most LAN switches forward traffic based on MAC addresses. This variety of LAN switch is sometimes called a frame switch. LAN switches are often categorized according to the method they use to forward traffic: cut-through packet switching or store-and-forward packet switching. Multilayer switches are an intelligent subset of LAN switches. An example of a LAN switch is the Cisco Catalyst 5000. Compare with multilayer switch.

LAPB Acronym for Link Access Procedure, Balanced. Data-link layer protocol in the X.25 protocol stack. LAPB is a bit-oriented protocol derived from HDLC.

LAPD Acronym for Link Access Procedure on the D channel. ISDN data-link layer protocol for the D channel. LAPD was derived from the LAPB protocol and is designed primarily to satisfy the signaling requirements of ISDN basic access. Defined by ITU-T Recommendations Q.920 and Q.921.

laser Light amplification by stimulated emission of radiation. Analog transmission device in which a suitable active material is excited by an external stimulus to produce a narrow beam of coherent light that can be modulated into pulses to carry data. Networks based on laser technology are sometimes run over SONET.



latency Delay between the time a device requests access to a network and the time it is granted permission to transmit. 2. Delay between the time when a device receives a frame and the time that frame is forwarded out the destination port.

leased line Transmission line reserved by a communications carrier for the private use of a customer. A leased line is a type of dedicated line.

LED Acronym for light emitting diode. Semiconductor device that emits light produced by converting electrical energy. Status lights on hardware devices are typically LEDs.

light emitting diode See LED.

line of sight Characteristic of certain transmission systems such as laser, microwave, and infrared systems in which no obstructions in a direct path between transmitter and receiver can exist.

link Network communications channel consisting of a circuit or transmission path and all related equipment between a sender and a receiver. Most often used to refer to a WAN connection. Sometimes referred to as a line or a transmission link.

Link Access Procedure on the D channel See LAPD.

Link Access Procedure, Balanced See LAPB.

link-state routing algorithm Routing algorithm in which each router broadcasts or multicasts information regarding the cost of reaching each of its neighbors to all nodes in the internetwork. Link-state algorithms create a consistent view of the network and are therefore not prone to routing loops, but they achieve this at the cost of relatively greater computational difficulty and more widespread traffic (compared with distance vector routing algorithms). Compare with distance vector routing algorithm.

LLC Acronym for Logical Link Control. Higher of the two data-link layer sublayers defined by the IEEE. The LLC sublayer handles error control, flow control, framing, and MAC-sublayer addressing. The most prevalent LLC protocol is IEEE 802.2, which includes both connectionless and connection-oriented variants.

local loop loop Line from the premises of a telephone subscriber to the telephone company CO. Route where packets never reach their destination, but simply cycle repeatedly through a constant series of network nodes.

loopback test Test in which signals are sent and then directed back toward their source from some point along the communications path. Loopback tests are often used to test network interface usability.

MAC Acronym for Media Access Control. Lower of the two sublayers of the data-link layer defined by the IEEE. The MAC sublayer handles access to shared media, such as whether token passing or contention will be used.

MAC address Standardized data-link layer address that is required for every port or device that connects to a LAN. MAC addresses are six bytes long and are controlled by the IEEE. Also known as a hardware address, MAC layer address, and physical address.

main distribution facility See MDF.



MAN Acronym for metropolitan-area network. Network that spans a metropolitan area. Generally, a MAN spans a larger geographic area than a LAN, but a smaller geographic area than a WAN.

MDF Acronym for main distribution facility. Primary communications room for a building. Central point of a star networking topology where patch panels, hub, and router are located.

Media Access Control See MAC.

megabit (Mb) A megabit is approximately 1 million bits.

megabits per second (Mbps) A standard measurement of the amount of data transferred over a network connection during a time period of one second.

megabyte (MB) A megabyte is approximately 1 million bytes (1,048,576 bytes exactly). A megabyte is sometimes referred to as a "meg."

megabytes per second(MBps) A standard measurement of the amount of data transferred over a network connection during a time period of one second.

megahertz (MHz) A megahertz is one million cycles per second. This is a common measurement of the speed of a processing chip, such as a computer microprocessor.

metropolitan-area network See MAN.

microprocessor A microprocessor is a silicon chip that contains a CPU.

modulation Process by which the characteristics of electrical signals are transformed to represent information. Modems perform modulation by taking a digital signal and altering it to an analog signal.

mouse port This port is designed for connecting a mouse to a PC.

multicast Single packets copied by the network and sent to a specific subset of network addresses. These addresses are specified in the destination address field. See broadcast.

multicast address Single address that refers to multiple network devices in a group. Synonymous with group address.

multiplexing Scheme that allows multiple logical signals to be transmitted simultaneously across a single physical channel.

NAK Acronym for negative acknowledgment. Response sent from a receiving device to a sending device indicating that the information received contained errors.

narrowband See baseband.

negative acknowledgment See NAK.

network Collection of computers, printers, routers, switches, and other devices that are able to communicate with each other over some transmission medium. 2. Command that assigns a NIC-based address to which the router is directly connected. 3. Command that specifies any directly connected networks to be included.

https://elms.faa.gov/skillsoft/cbtlib/219381/eng/references/glossary.html#NAK



network card The network card is an expansion board inserted into a computer so that the computer can be connected to a network.

network interface card See NIC.

network layer Layer 3 of the OSI reference model. This layer provides connectivity and path selection between two end systems. The network layer is the layer at which routing occurs. Corresponds roughly with the path control layer of the SNA model.

NIC Acronym for network interface card. Board that provides network communication capabilities to and from a computer system. Also called an adapter.

nonvolatile RAM See NVRAM.

NVRAM Acronym for nonvolatile RAM. RAM that retains its contents when a unit is powered off.

OIR Acronym for online insertion and removal. Feature that permits the addition, the replacement, or the removal of cards without interrupting the system power, entering console commands, or causing other software or interfaces to shut down. Sometimes called hot swapping or power-on servicing.

online insertion and removal See OIR.

Open System Interconnection See OSI.

OSI Acronym for Open System Interconnection. International standardization program created by ISO and ITU-T to develop standards for data networking that facilitate multivendor equipment interoperability.

out-of-band signaling Transmission using frequencies or channels outside the frequencies or channels normally used for information transfer. Out-of-band signaling is often used for error reporting in situations in which in-band signaling can be affected by whatever problems the network might be experiencing. Contrast with in-band signaling.

packet Logical grouping of information at Layer 3 that includes a header containing control information and a PDU from the same or upper layer. Packets are used to refer to network layer units of data. The terms datagram, frame, message, and segment are also used to describe logical information groupings at various layers of the OSI reference model and in various technology circles.

PAP Acronym for Password Authentication Protocol. Authentication protocol that allows PPP peers to authenticate one another. The remote router attempting to connect to the local router is required to send an authentication request. Unlike CHAP, PAP passes the password and host name or username in the clear (unencrypted). PAP does not itself prevent unauthorized access, but merely identifies the remote end. The router or access server then determines if that user is allowed access. PAP is supported only on PPP lines.

parallel port The parallel port is an interface capable of transferring more than one bit simultaneously through a single cable containing multiple conductors. It is used to connect external devices, such as printers and internal devices to hard drives.

Password Authentication Protocol See PAP.



patch panel An assembly of pin locations and ports that can be mounted on a rack or wall bracket in the wiring closet. Patch panels act like switchboards that connect workstation cables to each other and to the outside.

path cost See cost.

PCB Acronym for printed circuit board. The PCB is a thin plate on which chips (integrated circuits) and other electronic components are placed.

PCI Acronym for peripheral component interconnect. A standard for connecting peripherals to a personal computer. Used primarily in Pentium- and AMD-based systems, it is processor independent, therefore can work with other processor architectures.

PCMCIA Acronym for Personal Computer Memory Card International Association. PCMCIA is an organization that has developed a standard for small, credit-card sized devices, called PC cards. Originally designed for adding memory to portable computers, the PCMCIA standard has been expanded several times and is now suitable for many types of devices.

PDU Acronym for protocol data unit. OSI term for a layer-specific grouping of data.

peripheral component interconnect See PCI.

Personal Computer Memory Card International Association See PCMCIA.

physical layer Layer 1 of the OSI reference model. The physical layer defines the electrical, mechanical, procedural, and functional specifications for activating, maintaining, and deactivating the physical link between end systems. Corresponds with the physical control layer in the SNA model.

ping Acronym for packet internet groper. ICMP echo message and its reply. Often used in IP networks to test the reachability of a network device.

power cord The power cord is used to connect an electrical device to an electrical outlet in order to provide power to the device.

presentation layer Layer 6 of the OSI reference model. This layer ensures that information sent by the application layer of one system will be readable by the application layer of another. The presentation layer is also concerned with the data structures used by programs and therefore negotiates data transfer syntax for the application layer.

PRI Acronym for Primary Rate Interface. ISDN interface to primary rate access. Primary rate access consists of a single 64-Kbps D channel plus 23 (T1) or 30 (E1) B channels for voice or data.

Primary Rate Interface See PRI.

printed circuit board See PCB.

process A single thread of computation to achieve a specific goal performed within a microprocessor or software.

PROM



Acronym for programmable read-only memory. ROM that can be programmed using special equipment. PROMs can be programmed only once. Compare with EPROM.

propagation delay Time required for data to travel over a network, from its source to its ultimate destination.

protocol Formal description of a set of rules and conventions that govern how devices on a network exchange information.

protocol data unit See PDU.

QoS Acronym for quality of service. Measure of performance for a transmission system that reflects its transmission quality and service availability.

QoS parameters Acronym for quality of service parameters. Parameters that control the amount, performance, and reliability of traffic on a transmission device on a network.

query Message used to inquire about the value of some variable or set of variables.

queue Generally, an ordered list of elements waiting to be processed. 2. In routing, a backlog of packets waiting to be forwarded over a router interface.

queuing delay Amount of time that data must wait before it can be transmitted onto a statistically multiplexed physical circuit.

RAM Acronym for random-access memory. Also known as read-write memory, RAM can have new data written into it as well as stored data read from it. If the computer is turned off or loses power, all data stored in RAM is lost unless the data was previously saved to disk.

random-access memory See RAM.

RARP Acronym for Reverse Address Resolution Protocol. Protocol in the TCP/IP stack that provides a method for acquiring an IP address based on MAC addresses.

Reverse Address Resolution Protocol See RARP.

ring topology Network topology that consists of a series of repeaters connected to one another by unidirectional transmission links to form a single closed loop. Each station on the network connects to the network at a repeater. While logically a ring, ring topologies are most often organized in a closed-loop star.

RIP Acronym for Routing Information Protocol. IGP supplied on many UNIX systems. The most common IGP in the Internet. RIP uses hop count as a routing metric.

RJ connector Acronym for registered jack connector. Standard connectors originally used to connect telephone lines. RJ connectors are now used for telephone connections and for 10BASE-T and other types of network connections. RJ-11, RJ-12, and RJ-45 are popular types of RJ connectors.

ROM Acronym for read-only memory. ROM is computer memory on which data has been prerecorded.

ROM Acronym for read-only memory. Nonvolatile memory that can be read, but not written, by the microprocessor.

route



Path through an internetwork. routed protocol

Protocol that can be routed by a router. A router must be able to interpret the logical internetwork as specified by that routed protocol. Examples of routed protocols include AppleTalk, DECnet, and IP.

router Network layer device that uses one or more metrics to determine the optimal path along which network traffic should be forwarded. Routers forward packets from one network to another based on network layer information. Generally called a gateway when used by a device to forward traffic off a local network and that does not participate in routing or multiple networks.

routing Process of finding a path to a destination host. Routing is very complex in large networks because of the many potential intermediate destinations a packet might traverse before reaching its destination host.

Routing Information Protocol See RIP.

routing metric Method by which a routing algorithm determines that one route is better than another. This information is stored in routing tables. Metrics include bandwidth, communication cost, delay, hop count, load, MTU, path cost, and reliability. Sometimes referred to simply as a metric.

routing protocol Protocol that accomplishes routing through the implementation of a specific routing algorithm. Examples of routing protocols include IGRP, OSPF, and RIP.

routing table Table stored in a router or some other internetworking device that keeps track of routes to particular network destinations and, in some cases, metrics associated with those routes.

RS-232 Popular physical-layer interface. Now known as EIA/TIA-232.

RS-422 Balanced electrical implementation of EIA/TIA-449 for high-speed data transmission. Now referred to collectively with RS-423 as EIA-530.

RS-423 Unbalanced electrical implementation of EIA/TIA-449 for EIA/TIA-232 compatibility. Now referred to collectively with RS-422 as EIA-530.

RS-449 Popular physical-layer interface. Now known as EIA/TIA-449.

SAN Acronym for storage area network. An emerging data communications platform that interconnects servers and storage at gigabaud speeds. By combining LAN networking models with the core building blocks off server performance and mass storage capacity, SAN eliminates the bandwidth bottlenecks and scalability limitations imposed by previous SCSI busbased architectures.

SDLC Acronym for Synchronous Data Link Control. SNA data-link layer communications protocol. SDLC is a bit-oriented, full-duplex serial protocol that has spawned numerous similar protocols, including HDLC and LAPB.

serial port This interface can be used for serial communication in which only one bit is transmitted at a time.

server Node or software program that provides services to clients.

session layer



Layer 5 of the OSI reference model. This layer establishes, manages, and terminates sessions between applications and manages data exchange between presentation layer entities. Corresponds to the data-flow control layer of the SNA model.

Simple Network Management Protocol See SNMP.

slow switching Packet processing performed at process level speeds, without the use of a route cache. Contrast with fast switching.

SNMP Acronym for Simple Network Management Protocol. Network management protocol used almost exclusively in TCP/IP networks. SNMP provides a means to monitor and control network devices, and to manage configurations, statistics collection, performance, and security.

sound card A sound card is an expansion board that handles all sound functions.

SRAM Type of RAM that retains its contents for as long as power is supplied. SRAM does not require constant refreshing, like DRAM. Compare with DRAM.

star topology LAN topology in which end points on a network are connected to a common central switch by point-to-point links. A ring topology that is organized as a star implements a unidirectional closed-loop star, instead of point-to-point links.

statistical multiplexing Technique whereby information from multiple logical channels can be transmitted across a single physical channel. Statistical multiplexing dynamically allocates bandwidth only to active input channels, making better use of available bandwidth and allowing more devices to be connected than with other multiplexing techniques. Also referred to as statistical time-division multiplexing or stat mux.

storage area network See SAN.

STP Acronym for shielded twisted-pair. See UTP.

Synchronous Data Link Control See SDLC.

synchronous transmission Term describing digital signals that are transmitted with precise clocking. Such signals have the same frequency, with individual characters encapsulated in control bits (called start bits and stop bits) that designate the beginning and end of each character.

T1 Digital WAN carrier facility. T1 transmits DS-1-formatted data at 1.544 Mbps through the telephone-switching network, using AMI or B8ZS coding.

TDM Acronym for time-division multiplexing. Technique in which information from multiple channels can be allocated bandwidth on a single wire based on preassigned time slots. Bandwidth is allocated to each channel regardless of whether the station has data to transmit. See FDM.

terminal Simple device at which data can be entered or retrieved from a network or device. Generally, terminals have a monitor and a keyboard, but no processor or local disk drive.

TFTP Acronym for Trivial File Transfer Protocol. Simplified version of FTP that allows files to be transferred from one computer to another over a network, usually without the use of client authentication (for example, username and password).



time-division multiplexing See TDM.

token passing Network media access method by which network devices access the physical medium in an orderly fashion based on possession of a small frame called a token. Contrast with circuit switching and contention.

Token Ring An IEEE 802 LAN that makes use of token passing on a physical or logical ring topology.

transport layer Layer 4 of the OSI reference model. This layer is responsible for reliable network communication between end nodes. The transport layer provides mechanisms for the establishment, maintenance, and termination of virtual circuits, transport fault detection and recovery, and information flow control. Corresponds to the transmission control layer of the SNA model.

Trivial File Transfer Protocol See TFTP.

UART Universal Asynchronous Receiver/Transmitter. Integrated circuit, attached to the parallel bus of a computer, used for serial communications. The UART translates between serial and parallel signals, provides transmission clocking, and buffers data sent to or from the computer.

UBR Acronym for unspecified bit rate. QoS class defined by the ATM Forum for ATM networks. UBR allows any amount of data up to a specified maximum to be sent across the network, but there are no guarantees in terms of cell loss rate and delay. Compare with ABR (available bit rate), CBR, and VBR.

UDP Acronym for User Datagram Protocol. Connectionless transport layer protocol in the TCP/IP protocol stack. UDP is a simple protocol that exchanges datagrams without acknowledgments or guaranteed delivery, requiring that error processing and retransmission be handled by other protocols. UDP is defined in RFC 768.

UL Acronym for Underwriters Laboratories. Independent agency within the United States that tests product safety.

unicast Message sent to a single network destination. Compare with broadcast and multicast.

unicast address Address specifying a single network device.

uninterruptible power supply See UPS.

Universal Asynchronous Receiver/Transmitter See UART.

unshielded twisted-pair See UTP.

unspecified bit rate See UBR.

UPS Acronym for uninterruptible power supply. Backup device designed to provide an uninterrupted power source in the event of a power failure. They are commonly installed on all file servers and wiring hubs.

User Datagram Protocol See UDP.

UTP



Acronym for unshielded twisted-pair. Four-pair wire medium used in a variety of networks. UTP does not require the fixed spacing between connections that is necessary with coaxial-type connections. There are five types of UTP cabling commonly used: Category 1 cabling, Category 2 cabling, Category 3 cabling, Category 4 cabling, and Category 5 cabling. Compare with STP.

V.32 ITU-T standard serial-line protocol for bidirectional data transmissions at speeds of 4.8 or 9.6 kbps.

V.34 ITU-T standard that specifies a serial line protocol. V.34 offers improvements to the V.32 standard, including higher transmission rates (28.8 kbps) and enhanced data compression. Compare with V.32.

V.35 ITU-T standard describing a synchronous, physical-layer protocol used for communications between a network access device and a packet network. V.35 is most commonly used in the United States and in Europe, and is recommended for speeds up to 48 kbps.

VBR Acronym for variable bit rate. QoS class defined by the ATM Forum for ATM networks. VBR is subdivided into a real time (RT) class and non-real time (NRT) class. VBR (RT) is used for connections in which there is a fixed timing relationship between samples. VBR (NRT) is used for connections in which there is no fixed timing relationship between samples, but that still need a guaranteed QoS. See UBR.

vertical cabling Backbone cabling.

virtual circuit Logical circuit created to ensure reliable communication between two network devices. A virtual circuit is defined by a VPI/VCI pair, and can be either permanent (a PVC) or switched (an SVC). Virtual circuits are used in Frame Relay and X.25. In ATM, a virtual circuit is called a virtual channel. Sometimes abbreviated VC.

Virtual LAN See VLAN.

Virtual Private Network See VPN.

virtual terminal Software driven terminal emulation to provide the same functionality of a local terminal or console to a remote location or device.

VLAN Acronym for virtual LAN. Group of devices on a LAN that are configured so that they can communicate as if they were attached to the same wire, when in fact they are located on a number of different LAN segments. Because VLANs are based on logical instead of physical connections, they are extremely flexible.

VPN Acronym for Virtual Private Network. A logical network created through the use of encapsulation or tagging techniques.

WAN Acronym for wide-area network. Data communications network that serves users across a broad geographic area and often uses transmission devices provided by common carriers. Frame Relay, SMDS, and X.25 are examples of WANs.

wideband See broadband.

wildcard mask 32-bit quantity used in conjunction with an IP address to determine which bits in an IP address should be ignored when comparing that address with another IP address. A wildcard mask is specified when setting up access lists.

https://elms.faa.gov/skillsoft/cbtlib/219381/eng/references/glossary.html#Vn46n32



window Number of octets that the receiver is willing to accept.

window size Refers to the number of messages that can be transmitted while awaiting an acknowledgment.

wire map Feature provided by most cable testers. Used to test twisted-pair cable installations, it shows which wire pairs connect to which pins on the plugs and sockets.

wiring closet Specially designed room used for wiring a data or voice network. Wiring closets serve as a central junction point for the wiring and wiring equipment that is used for interconnecting devices.

workgroup Collection of workstations and servers on a LAN that are designed to communicate and exchange data with one another.

workgroup switching Method of switching that provides high-speed (100-Mbps) transparent bridging between Ethernet networks and high-speed translational bridging between Ethernet and CDDI or FDDI.

X terminal Terminal that allows a user simultaneous access to several different applications and resources in a multivendor environment through implementation of X Windows.

X Windows Distributed, network-transparent, device-independent, multitasking windowing and graphics system originally developed by MIT for communication between X terminals and UNIX workstations.

X.25 ITU-T standard that defines how connections between DTE and DCE are maintained for remote terminal access and computer communications in PDNs. X.25 specifies LAPB, a data-link layer protocol, and PLP, a network-layer protocol. Frame Relay has to some degree superseded X.25.

10 Mbps Approximately 10 million bits per second, an information transfer rate.

100BASE-FX 100-Mbps baseband Fast Ethernet specification using two strands of multimode fiberoptic cable per link. To guarantee proper signal timing, a 100BASE-FX link cannot exceed 1312 feet (400 meters) in length. Based on the IEEE 802.3 standard.

100BASE-T 100-Mbps baseband Fast Ethernet specification using UTP wiring. Like the 10BASE-T technology on which it is based, 100BASE-T sends link pulses over the network segment when no traffic is present. However, these link pulses contain more information than those used in 10BASE-T. Based on the IEEE 802.3 standard.

100BASE-T4 100-Mbps baseband Fast Ethernet specification using four pairs of Category 3, 4, or 5 UTP wiring. To guarantee proper signal timing, a 100BASE-T4 segment cannot exceed 328 feet (100 meters) in length. Based on the IEEE 802.3 standard.

100BASE-TX 100-Mbps baseband Fast Ethernet specification using two pairs of either UTP or STP wiring. The first pair of wires is used to receive data; the second is used to transmit. To guarantee proper signal timing, a 100BASE-TX segment cannot exceed 328 feet (100 meters) in length. Based on the IEEE 802.3 standard.

100BASE-X 100-Mbps baseband Fast Ethernet specification that refers to the 100BASE-FX and 100BASE-TX standards for Fast Ethernet. Based on the IEEE 802.3 standard.

10BASE2



10-Mbps baseband Ethernet specification using 50-ohm thin coaxial cable. 10BASE2, which is part of the IEEE 802.3 specification, has a distance limit of 185 meters per segment.

10BASE5 10-Mbps baseband Ethernet specification using standard (thick) 50-ohm baseband coaxial cable. 10BASE5, which is part of the IEEE 802.3 baseband physical layer specification, has a distance limit of 500 meters per segment.

10BASE-F 10-Mbps baseband Ethernet specification that refers to the 10BASE-FB, 10BASE-FL, and 10BASE-FP standards for Ethernet over fiber-optic cabling.

10BASE-FB 10-Mbps baseband Ethernet specification using fiber-optic cabling. 10BASE-FB is part of the IEEE 10BASE-F specification. It is not used to connect user stations, but instead provides a synchronous signaling backbone that allows additional segments and repeaters to be connected to the network. 10BASE-FB segments can be up to 2000 meters long.

10BASE-FL 10-Mbps baseband Ethernet specification using fiber-optic cabling. 10BASE-FL is part of the IEEE 10BASE-F specification and, while able to interoperate with FOIRL, is designed to replace the FOIRL specification. 10BASE-FL segments can be up to 1000 meters long if used with FOIRL, and up to 2000 meters if 10BASE-FL is used exclusively.

10BASE-FP 10-Mbps fiber-passive baseband Ethernet specification using fiber-optic cabling. 10BASE-FP is part of the IEEE 10BASE-F specification. It organizes a number of computers into a star topology without the use of repeaters. 10BASE-FP segments can be up to 500 meters long.

10BASE-T 10-Mbps baseband Ethernet specification using two pairs of twisted-pair cabling (Category 3, 4, or 5): one pair for transmitting data and the other for receiving data. 10BASE-T, which is part of the IEEE 802.3 specification, has a distance limit of approximately 328 feet (100 meters) per segment.



H. Quizzes’ Answers

i Answer

The backplane is a part of the computer that allows external devices to be connected, the bus connects all the internal computer components to the CPU, the CPU is where most of the calculations take place, expansion slots are openings in a computer into which you can insert a circuit board, and the floppy drive is a disk drive that can read and write to floppy disks.

The backplane is a part of the computer that allows external devices to be connected. It contains components such as a power cord, a serial port, a mouse port, and a parallel port.

The bus connects internal components to the CPU. Data is transmitted through the computer via its collection of wires.

The CPU is the computer's "brain". It uses a silicion-based microprocessor that performs calculations and is contained inside the CPU.

You can insert a circuit board or NIC into expansion slots.

A floppy drive can read and write to floppy disks, whereas CD-ROMs and hard disks require a different type of drive (rarely used nowadays).

ii Answer

Laptops generally use less power than PCs, the components are smaller, and the slots you connect devices to are called PCMCIA slots instead of expansion slots.

Option 1 is incorrect. It is more difficult to remove the components from a laptop than those from a PC because laptop components are designed to fit together in a smaller physical space.

Option 2 is correct. Laptops generally use less power than PCs as they are designed to operate using a battery.

Option 3 is correct. Laptop components are smaller than those in a PC because they need to fit into a smaller physical space.

Option 4 is correct. The slots you connect devices to are called expansion slots in a PC and PCMCIA slots in a laptop. For example, you can connect NICs, modems, and hard drives.

iii Answer

When selecting a NIC for a network, you should take into account the type of media, network, and expansion slot.

Option 1 is incorrect. The type of CPU is not relevant when selecting a NIC for a network. A NIC is designed to work with a specific type of expansion slot, regardless of the CPU type.

Option 2 is correct. The type of media is important when selecting a NIC because it determines the type of port or connector needed.

Option 3 is correct. The type of network is important when selecting a NIC. For example, if the network is an Ethernet LAN, then you need an Ethernet NIC. For a Token Ring LAN, you need a Token Ring NIC.

Option 4 is correct. The type of expansion slot is important when selecting a NIC. For example, PCI slots are faster than ISA slots. Using a faster slot means the data from the network is received and processed faster by the computer.

iv Answer

Before you install a NIC, you must know how to configure the network card, how to use the network card diagnostics, and be able to resolve hardware resource conflicts.



Option 1 is correct. You must be able to resolve hardware resource conflicts such as IRQ, I/O base address, and DMA.

Option 2 is incorrect. You don't need to be familiar with all types of network cards because some have specialized functions in networks and are not commonly used, or require specific technical expertise.

Option 3 is correct. You need to know how the network card is configured. You should use the vendor-supplied diagnostics and loopback test.

Option 4 is correct. You need to know how to use the network card diagnostics by using jumpers, "plug-and-play" software, and EPROM.

v Answer

A bit equals 1 or 0 in binary format, a byte is equal to 8 bits, a GB is equal to approximately one billion bytes, a KB is equal to approximately 1000 bytes, an Mb is equal to approximately one million bits, and an MB is equal to approximately one million bytes.

A bit is the smallest unit of data in a computer.

A byte is equal to eight bits and represents one character of alphanumeric data.

A gigabyte is also equal to one thousand megabytes.

A kilobyte is 1024 bytes exactly.

A megabit is equal to 1,048,576 bits exactly.

A megabyte is equal to 1,048,576 bytes exactly.

vi Answer

The binary equivalent of 197 is 11000101.

Option 1 is incorrect. 10000101 is actually the binary equivalent of 133.


Option 3 is correct. 11000101 is the binary equivalent of 197. From right to left, the values are as follows: the first 1 is represented by the place value "1", the second 1 is "4", the third 1 is ""64", and the fourth 1 is "128". Therefore, you add 1+4+64+128 to give a result of 197.


vii Answer

The decimal equivalent of 11011000 is 216.

viii Answer

5689F1EC and 0x5689F1EC are both hexadecimal equivalents of 1010110100010011111000111101100.

Option 1 is incorrect. 1451880940 is the decimal equivalent of 1010110100010011111000111101100.

Option 2 is correct. 5689F1EC is the hexadecimal equivalent of 1010110100010011111000111101100. Add a 0 to the left to make groups of 4. (0)101 is 5, 0110 is 6, 1000 is 8, 1001 is 9, 1111 is F, 0001 is 1, 1110 is E, and 1100 is C.

Option 3 is incorrect. AD13E3D4 is not the hexadecimal equivalent of 1010110100010011111000111101100. You should be careful not to divide the groups up into bits of four from right to left. They should be divided left to right.

Option 4 is correct. 0x5689F1EC is the hexadecimal equivalent of 1010110100010011111000111101100. 0x is commonly used in front of the hexadecimal number by computers and software.



ix Answer

The binary equivalent of 52AC45123 is 10100101010110001000101000100100011, 589FE is 1011000100111111110, 56ED45 is 10101101110110101000101, and 63AC2 is 1100011101011000010.

10100101010110001000101000100100011 is the binary equivalent of 52AC45123. 0101 is the binary equivalent of 5, 0010 is 2, 1010 is A, 1100 is C, 0100 is 4, 0101 is 5, 0001 is 1, 0010 is 2, and 0011 is 3.

10101101110110101000101 is the binary equivalent of 56ED45. 0101 is the binary equivalent of 5, 0110 is 6, 1110 is E, 1101 is D, 0100 is 4, and 0101 is 5.

1011000100111111110 is the binary equivalent of 589FE. 0101 is the binary equivalent of 5, 1000 is 8, 1001 is 9, 1111 is F, and 1110 is E.

110 0011 1010 1100 0010 is the binary equivalent of 63AC2. 0110 is the binary equivalent of 6, 0011 is 3, 1010 is A, 1100 is C, and 0010 is 2.

x Result

xi Result

xii Result

xiii 4. Answer



The OSI reference model defines the network functions that occur at each layer and describes how data makes its way from one application program to another throughout a network. It also specifies how information travels through networks.

Option 1 is correct. The OSI reference model is divided into seven layers, and each layer carries out a clearly defined function.

Option 2 is correct. In order to standardize the way data travels over a network, the OSI reference model specifies the process by which data should be transmitted.

Option 3 is correct. The OSI reference model makes it easier for vendors to educate customers on how data is transmitted throughout a network.

Option 4 is incorrect. The OSI reference model was developed in order to help companies move away from proprietary networking systems toward open systems that would ensure greater compatibility.

xiv Answer

The session layer manages the communication processes and data exchange between hosts.

Option 1 is incorrect. The network layer is concerned with connectivity and the routes selected for packets.

Option 2 is incorrect. The transport layer ensures data transport reliability.

Option 3 is incorrect. The presentation layer ensures that the data format is acceptable to the receiving application.

Option 4 is correct. The session layer establishes and manages sessions between hosts.

xv Answer

Correct ranking

Option Description

D Presentation The presentation layer adds the Layer 6 header to the data and passes it to the session layer.

E Session The session layer adds the Layer 5 header to the data and passes it to the transport layer.

F Transport The transport layer adds the Layer 4 header to the data and passes it to the network layer.

B Network The network layer adds the Layer 3 header to the data and passes it to the data-link layer.

A Data Link The data-link layer adds the Layer 2 header and the frame check sequence trailer to the data and passes it to the physical layer.

C Physical The physical layer transmits the data onto the physical connection.

xvi Answer



Encapsulation is the process that wraps data with the necessary protocol information before network transit. When this information is received it is checked for errors and stripped of its header and trailer in a process known as de-encapsulation. Peer-to-peer communication is the process that facilitates the communication between OSI peer layers during data transfer.

The process of encapsulation begins when data leaves the sender's pc. This data then travels through the seven layers of the OSI reference model, where each layer adds a header to the data. These headers ensure that the data is properly transmitted, and dealt with at the appropriate layer by the receiver.

The process of de-encapsulation begins when data is received. Firstly the information is passed to the data-link layer to see if there is an error in the data. Once no errors are detected, it is stripped of its header and sent on up into the network layer, and the headers are then stripped off by each subsequent layer.

Peer-to-peer communication is necessary so that packets can travel from the source to the destination. During this process, each layer communicates to its peer layer and exchanges information called PDUs.

xvii Answer

The transport layer deals with reliability, flow control, and error correction.

Option 1 is incorrect. The application layer handles high-level protocols and ensures that all data is properly packaged for the next layer.

Option 2 is incorrect. The Internet layer is responsible for the delivery of source packets from any network on the internetwork.

Option 3 is incorrect. Sometimes known as the host-to-network layer, the network access layer handles the details in the OSI physical and data-link layers.

Option 4 is correct. The transport layer provides for reliable network communications, ensuring the reliability of transmitted data.

Building a Network - Study Notes

Technology

Transcript of Building a Network - Study Notes