Networking

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INFOTECH Computer Education, Kishangarh (Raj) 9829171122

Chapter 1 - Network

Q1. What is a Computer Network ?

Computer Network : A computer network is a set of two or more interconnected computers and a set of

hardware devices.

Q2. What are the Goals / Advantages of a Network ?

1. Resource Sharing (Hardware and Software)

2. Reliability

3. Cost Factor

4. Communication Medium (Improves Communication)

Q3. Disadvantages of Networks ?

1. More Complex and Sophisticated

2. Network Management is also very complex

3. Implementation of Security is also complex

4. If central computer fails then whole network fails

Q4. What is a Node ?

A node refers to the computer that are attached to a network and are seeking to share resources of the

network.

Q4. What is a Server ?

A computer that facilitates the sharing of data, software and hardware resources on the network is

termed as a server.

Q5. Types of Servers ?

1. Non-dedicated Server : It is not completely dedicated for serving process. It is slower and requires

more memory. The network using such a server is known as master slave network.

2. Dedicated Server : it is used on bigger networks. it is completely dedicated for serving process. the

network using such a server is known as master slave network. Various types of dedicated servers are

File server, modem server, print server etc.



Q6. What is a Network Interface Unit ?

A Network Interface Unit is an interpreter that helps establilsh cmmunication between the server and

workstation.

Q7. What is a MAC Address ?

A MAC address refers to the physical address assigned by NIC Manufacturer.

Q8. What is IP Address ?

Every machine on a TCP/IP network has a unique identifying number is called an IP Address. IP addresses

are written in dotted decimal form like

192.168.2.1

Q9. What is a Domain Name ?

A domain name is a unique name assigned to a website situated at a web server.

Q10. Parts of a Domain Name ?

1. www : world wide web

2. name describing the website : selected by the website owner

3. TLD (top level domain) : describes the type or location of website like .edu, .com, .net, .in, .fr etc

Q11. What is Domain Name Resolution ?

Domain Name Resolution refers to the process of obtaining corresponding IP address from a domain

name.

Q12. What is a Network Topology ?

The pattern of interconnection of nodes in a network is called the topology of a network .

Q13. What are the factors that affect the selection of network topology ?

1. Cost

2. Flexibility

3. Reliability

Q14. Types of Topology ?

1. Point to Point Link : A point to point network is normally a link created between two machines for

the function of transmission and reception of data.



2. Star Topology : in this topology a central node is connected to each individual machine throught a

seperate path.

Advantages

1. Easy to Implement and service

2. One Device per connection

3. Centralized control and diagnosis

4. Simple protocols

Disadvantages

1. Long Cable Required

2. Difficult to Expand

3. Central Node Dependency

3. Bus or Linear Topology : It consists of a single cable(normally coxial) onto which various nodes are

attached.

Advantages.

1.Short Cable Length and Simple Wiring Layout

2. Easy to Implement and Easy to Extend

3. Faster Data Transmission Speed



Disadvantages

1. Fault Detection and diagnosis is difficult

2. Needs repeater

3. Nodes must be Intelligent

4. If Central Cable (Bus) Fails, whole network goes down

4. Ring Topology : In this topology each node is connected to two and only two neighbouring nodes in a

circular ring architecture.

Advantages

1. Short Cable Lenght

2. No Wiring Closet Space required

3. Very Suitable for Optical Fibers

Disadvantages

1. Node Failure Causes the Network Failure

2. Difficult to Diagnose Faults

3. Network reconfiguration is Difficult

5. Tree Topology : It is a variation of tree topology. It is in the form of Tree Shape.

6. Graph Topology : In this topology nodes are connected together in an arbitrary fashion. A link may or

may not connect two or more nodes.



7. Mesh Topology : In this topology each node is connected to more than one node to provide an

alternative route in the case of failure.

8. Fully Connected : In this topology each node is connected to every other node of the network.

Types of Network :

On the Basis of Geographical Spread, types of network can be

1. LAN (Local Area Network) : Between an office, a building or a factory

2. MAN (Metropolitian Area Network) : Between two cities

3. WAN (Wide Area Network) : Between two or more countries

4. PAN (Personal Area Network) : Between the range of reachability of an individual person



Difference Between LAN and WAN

LAN WAN

1. Diameter of not more than a few kms span entire countries

2. data rate of at least several mbps data rate less than 1 mbps

3. ownership by a single organization owned by multiple organization

4. very low error rates higher error rates

Internet Services

1. WWW : World wide web.

2. E-mail

3. Online Messaging

4. Newsgroup : it is also known as bulletin board where various person shares latest news

5. Real time streaming : it provides realtime audio or video

6. RSS : Really Simple Syndication -> it lets you browse through headlines which you cilck on to open in

your web browser.

7. Telephony : This allows speech to be conveyed as digital data. it is telephone over internet

8. Internet Backup

9. FTP : file transfer protocol -> allows to transfer files over the web

10. Telnet : this lets you log onto a remote machine.

Transmission Media

Transmission media or communication channel of network means connecting cables or media.

Types of Transmission Media

(a) Guided Media (Wired Media)

(i) Twisted Pair

(1) STP (Shielded Twisted Pair)

(2) UTP (Unshielded Twisted Pair)

(ii) Coxial Cable

(1) Category 1 (BaseBand)

(2) Category 2 (Broadband)

(iii) Fibre Optic Cable

(1) Single Mode Fibre

(2) Multimode Fibre

(*) Step Index Fibre

(*) Graded Index Fibre

(b) Unguided Media (Wireless Media)

(i) Microwave

(1) Terristeral



(2) Satellite

(ii) Radiowave

(iii) Bluetooth

(iv) Lazer

(v) Infrared

Twisted Pair : It is the most common from of wiring with least transmission speed . The twisting of wires

reduces crosstalk.

Q15. What is crosstalk

The bleeding of a signal from one wire to antoher and which can corrupt signal and cause network

errors is called crosstalk.

Advantages of Twisted Pair

1. It is simple

2. It is physically flexible

3. It can be easily connected

4. It is easy to install and maintain

5. It has a low weight

5. It is very inexpensive

Communication Media

Wired/Guided

Twisted Pair Coxial Cable

Fibre Optic Cable

Wireless/Unguided

Microwave Radiowave

Bluetooth Lazer

Infrared



Disadvantages of Twisted Pair

1. High attenuation and can't carray signal over long distances without repeaters

2. Low bandwidth

3. it supports maximum data rates of 1 mbps

Coxial Cable : This type of wire consists of a solid wire core surrouned by one or more foil or wire shields

and each seperated by some kind of plastic insulator

Advantages :

1. Data transfer Speed is considerably better

2. Can be used as the basis for a shared cable network

3. can be used for broadband transmission.

4. Offer higher bandwidth upto 400 MBPS

Disadvantages

1. Expensive compared to twisted pair

2. Not compatible with twisted pair

Optical Fibers : This wire consist of thin strands of glass fibers that carray light from source at one end of

the fiber and detector at the other end. This cable consists of three peices

1. The core

2. The cladding

3. Protective Coating

Advantages :



1. immune to electrical and magnetic interference and noise bcoz informatin travels in the form of light

beam

2. highly suitable for harsh industrial environments

3. guarantees secure transmission and has a very hight transmission capacity

4. can be used for braodband transmission bcoz of high capacity

Disadvantages

1. Installation is very difficult

2. Connecting two fibers together is a very difficult task

3. Because of noise immunity optical fibers are virtualy impossible to tap

4. Light can reach the reciever out of the phase

5. Connection losses are common problems

6. Fiber optic cables are more difficult to solder

7. They are the most expensive of all the cables.

Microwave : Microwave signals are similar to radio and television signals and are used for long distance

communication. It is a wireless transmission medium

Advantages

1. it proves cheaper than digging trenches for laying cables

2. it offers freedom from land acquisition rights

3. it offers ease of communication over difficult terrain

4. Microwave have the ability to communicate over oceans

Disadvantages

1. it is an insecure medium

2. Signals from a single antenna may split up and propogate by different paths to reciever

3. it is suspectable to weather effects like rain , stroms etc

4. Bandwidth allocation is extrememely limited

5. Cost of design, implementation and maintainance is very high

Radio Wave : it makes use of radio frequencies to transmit information



Advantages :

1. Radio wave transmission offers mobility

2. Proves cheaper than digging trenches for laying cables

3. Offers freedom from land acquision rights

4. it offers ease of communication over difficult terrain.

Disadvantages

1. it is insecure medium

2. it is supectible to weather effects like rains, stroms etc

Satellite : When the geographical distance is too much or across the oceans than we use satellite

communication media. in this the earth station consists of a satellite dish that functions as an antenna

and communication equipment to transmit and recieve data from satellite from space.

Advantages :

1. Area of coverage is quite large

2. Satellite is best alternative to laying cable etc

3. Heavy usage of intercontinental traffic makes it more attractive

4. It can cover large area of earth

Disadvantages

1. Technological limitations

2. Over crowding of available bandwidth due to low antenna gains

3. High investment cost

4. High atmospheric losses above 30 Ghz limit frequencies

Other Unguided Media

1. Infrared : line of sight communication mainly used for tv remotes etc

2. Lazer : line of sight communication mainly used for building to building communicatin



3. Bluetooth : spread spectrum communication mainly used for mobile communication etc

Network Devices

1. Modem : A modem is a computer peripheral that allows you to cnnect and communicate with other

computers via telephone lines. It is called MO(Modulator) DEM (Demodulator). it convers digital signals

to analog at the transmitter end and analog to digital at the receiver end.

Three Types of Modulation

1. AM - Amplitude Modulation

2. FM - Frequency Modulation

3. PM - Phase Modulation

Types of Modem

1. Internal Modem : it is fixed within the CPU

2. External Modem : it is connected outside the CPU as a seperate device.

HUB : It is a hardware that is used to connect several computers toghether. It is also called as

concentrator. Hub is of two types :

1. Active HUB : it amplify the signal as it mves from one connected device to antoher. These are like

repeaters.

2. Passive HUB : it allows the signal to pass data from one computer to another without any change.

Switch : it is a device that is used to segment networks into different subnetworks called subnets or lan

segments



Repeater : It is a device that amplifies and restores signals for long distance transmission

Gateway : A gateway is a network device that connects dissimilar networks. It establishes an intelligent

connection between a local network and external networks with completely different structures.

Bridge : It is a device which is used to connect two local area networks or two segments of the same

LAN.

Router : It is a network device that connects multiple networks irrespective of thier protocol. The main

function of a router is to find the best route for a network packet to reach the destination.



Q16. What is snooping

It refers to unauthorized access of someone else's data email, computer activity or data communication.

Q17. What is Eavesdropping

It is the act of secretly listening or intercepting someone else's private communication/data/information

Q18. What is DOS (Denial of Service)

DOS attacks are those attacks that prevent the legitimate users of the system from accessing or using

the resources information, or capabilities of the system.

Networking

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