Chapter 9

p. 6

WWW.PALINFONET.COMWWW.PALINFONET.COM

Communications

What are computer communications?

Nextp. 460 Fig. 9-1

set-top boxes

mainframecomputers

smartphones

notebookcomputers servers

Web-enabledPDAs

desktopcomputers

Tablet PCs

GPS receivers

Process in which two or more computers or devices transfer data, instructions, and information

Uses of Computer CommunicationsWhat are some uses of communications technology?

Nextp. 463

WebWebWebWebInternetInternetInternetInternet E-MailE-MailE-MailE-Mail

InstantInstantMessagingMessaging

InstantInstantMessagingMessaging FTPFTPFTPFTPNewsgroupsNewsgroupsNewsgroupsNewsgroupsChat RoomsChat RoomsChat RoomsChat Rooms

WebWebFoldersFolders

WebWebFoldersFolders

Fax Machine Fax Machine or Computer or Computer Fax/ModemFax/Modem

Fax Machine Fax Machine or Computer or Computer Fax/ModemFax/Modem

VideoVideoConferencingConferencing

VideoVideoConferencingConferencing

Uses of Computer CommunicationsWhat are Internet telephony and Internet printing?

p. 464 Next

Internet printing allows you to print to network printer from

anywhere in the world

Internet telephony enables you to talk to other people over the

InternetSometimes called

Voice over IP

Uses of Computer CommunicationsWhat are Web services?

Nextp. 464 Fig. 9-4

Software that enables programmers to create applications that communicate with other remote computers

Uses of Computer CommunicationsWhat is a global positioning system (GPS)?

Nextp. 464 Fig. 9-7

Click to view Web Link,click Chapter 9, Click Web Linkfrom left navigation, then click GPSbelow Chapter 9

Step 1.GPS satellites orbit Earth. Every thousandth of a second, each satellite sends a signal that indicates its current position to the GPS server.

Step 2.A GPS receiver (such as in a car, a PDA, a watch, a handheld device, or a collar) determines its location on Earth by analyzing at least 3 separate satellite signals from the 24 satellites in orbit.

Click to view video

Uses of Computer CommunicationsWhat are voice mail and wireless messaging services?

Nextp. 468 Fig. 9-8

Voice mail is voice message converted to digital form Wireless messaging services include:

Text Messaging Instant Messaging Picture Messaging

Networks

What is a network?

Nextp. 469 Fig. 9-9

Collection of computers and devices connected via communications devices and transmissionmedia

Networks

What is a local area network (LAN)?

Nextp. 471 Fig. 9-10

Click to view Web Link,click Chapter 9, Click Web Linkfrom left navigation, then click LANbelow Chapter 9

Network in limited geographical area such as home or office building Metropolitan area

network (MAN) connects LANs in city or town

Networks

What is a wide area network (WAN)?

Nextp. 472 Fig. 9-11

Network that covers large geographic area using many types of media

Internet is world’s largest WAN

Networks

What is a client/server network?

Nextp. 472 Fig. 9-12

One or more computers act as server and other computers, or clients, access server

Networks

What is a peer-to-peer network?

Nextp. 473 Fig. 9-13

Simple network that connects fewer than 10 computers

Each computer, or peer, has equal capabilities

Networks

What is Internet peer-to-peer (P2P)?

Nextp. 473 Fig. 9-14

Click to view Web Link,click Chapter 9, Click Web Linkfrom left navigation, then click P2Pbelow Chapter 9

Enables users to connect to each other’s hard disks and exchange files directly

Networks

What is a bus network?

Nextp. 474 Fig. 9-15

All computers and devices connect to central cable,or bus

Example of network topology (layout of devices in network) Popular topologies are

bus, ring, and star

Networks

What is a ring network?

Nextp. 474 Fig. 9-16

Cable forms closed ring, or loop, with all computers and devices arranged along ring

Data travels from device to device around entire ring, in one direction

Networks

What is a star network?

Nextp. 475 Fig. 9-17

All devices connect to a central device, called hub

All data transferred from one computer to another passes through hub

Networks

What are Ethernet and token ring?

Nextp. 475

Click to view Web Link,click Chapter 9, Click Web Link from left navigation, then click Ethernetbelow Chapter 9

Ethernet technology allows computers to contend for access to network

If two computers send data at same time, a collision occurs and computers must send again

Token ring technology controls access to network by requiring devices to pass a special signal, called token

Networks

What are TCP/IP and 802.11?

Nextp. 476 Fig. 9-18

TCP/IP (Transmission Control Protocol/Internet Protocol) technology transmits data by breaking it up into small pieces, or packets Commonly used for Internet transmissions

802.11 is family of standards for wireless LANs

Networks

What is Bluetooth?

Nextp. 476 Fig. 9-19

Short-range radio waves transmitdatabetweenBluetoothdevices

Networks

What are IrDA, RFID, and Wireless Applications Protocol (WAP)?

Nextp. 476

Click to view Web Link,click Chapter 9, Click Web Linkfrom left navigation, then click WAPbelow Chapter 9

IrDAIrDAspecification allows data to be transferred wirelessly via infrared light waves

IrDAIrDAspecification allows data to be transferred wirelessly via infrared light waves

Wireless Applications Wireless Applications Protocol (WAP)Protocol (WAP) allow wireless mobile devices to access Internet

Wireless Applications Wireless Applications Protocol (WAP)Protocol (WAP) allow wireless mobile devices to access Internet

Click to view video

Radio Frequency Radio Frequency Identification (RFID)Identification (RFID) uses radio signals to communicatewith a tag placed in an object

Radio Frequency Radio Frequency Identification (RFID)Identification (RFID) uses radio signals to communicatewith a tag placed in an object

Communications Over the Telephone Network

What is the public switched telephone network (PSTN)?

Nextp. 480 Fig. 9-22

Worldwide telephone system that handles voice-oriented telephone calls

Communications Over the Telephone Network

What is a dial-up line?

Nextp. 480 Fig. 9-23

Temporary connection using telephone line for communications Costs no more than

making regular call Computers at any two

locations can establish a connection using modems and telephone network

Communications Over the Telephone Network

What is an ADSL (asymmetric digital subscriber line)?

Nextp. 482 Fig. 9-25

Click to view Web Link,click Chapter 9, Click Web Linkfrom left navigation, then click DSLbelow Chapter 9

Popular type of DSL (Digital Subscriber Line)

Faster when receiving data than when sending data Ideal for Internet

access

Communications Devices

What is a dial-up modem?

Next

Click to view Web Link,click Chapter 9, Click Web Linkfrom left navigation, then click Dial-Up Modems below Chapter 9

p. 483 Figs. 9-26–9-27

Converts digital signals to analog signals and vice versa Notebook computers often use PC Card modem

Communications Devices

What are ISDN and DSL modems?

Nextp. 484

Communications devices that send and receive digital ISDN and DSL signals

Communications devices that send and receive digital ISDN and DSL signals

Usually external devices in which one end connects to a telephone line and the other

end connects to a port on the system unit

Usually external devices in which one end connects to a telephone line and the other

end connects to a port on the system unit

Communications Devices

What is a network card?

Nextp. 485 Fig. 9-29

Adapter card, PC Card, or compact flash card that enables computer or device to access network

Sometimes called network interface card (NIC)

Communications Devices

What is a wireless access point?

Nextp. 485 Fig. 9-30

Central communications device that allows computers and devices to transfer data wirelessly among themselves or to wired network

Communications Devices

What is a router?

Nextp. 486 Fig. 9-31

Click to view Web Link,click Chapter 9, Click Web Linkfrom left navigation, then click Routersbelow Chapter 9

Connects computers and transmits data to correct destination on network

Routers forward data on Internet using fastest available path

Communications Devices

What is a hub?

Nextp. 486 Fig. 9-32

Device that provides central point for cables in network

Click to view animation

Home Networks

What is a home network?

Nextp. 487 Fig. 9-33

Click to view Web Link,click Chapter 9, Click Web Linkfrom left navigation, then click Home Networks below Chapter 9

Multiple computers connected in home

Several types of home networks Ethernet — connect

computers via cable Powerline cable —

use electrical lines in house Phoneline — use telephone lines HomeRF (radio frequency) — wireless

Communications Channel

How is a request sent over the Internet using a communications channel?

Nextp. 489 Fig. 9-34

Step 1. The sending device requests information using either a physical transmission media or a wireless transmission media.

Step 2. When the request leaves the ISP, it travels over T1 lines, microwave stations, earth-based stations, and communications satellites until it reaches the Internet backbone.

Step 3. The request travels over T3 lines along the Internet backbone.

Step 4. The Request travels over T1 lines until it reaches the destination network server.

Physical Transmission Media

What are twisted-pair cable and coaxial cable?

Nextp. 490 Fig. 9-36—9-37

Twisted-pair cable is used for telephone systems and network cabling Coaxial cable is often used for cable television wiring

Physical Transmission Media

What is fiber-optic cable?

Nextp. 491 Fig. 9-38

Capable of carrying significantly more data at faster speeds than wire cables

Less susceptible to interference (noise) and, therefore, more secure

Smaller size (thinner and lighter)

Wireless Transmission Media

What is a microwave station?

Nextp. 493 Fig. 9-41

Earth-based reflective dish used for microwave communications

Must transmit in straight line with no obstructions

Wireless Transmission Media

What is a communications satellite?

Nextp. 494 Fig. 9-42

Space station that receives microwave signals from earth-based station, amplifies signals, and broadcasts signals back to any number of earth-based stations