Chapter 9

Chapter 9 Communications and Networks

Chapter 9 Objectives Discuss the components required for successful communications Identify various sending and receiving devices

Explain the purpose of communications software Describe various types of lines for communications over the telephone network

Describe uses of computer communications

Describe commonly used communications devices List advantages of using a network Discuss different ways to set up a home network Differentiate among client/server, peer-to-peer, and P2P networks

Identify various physical and wireless transmission media

Describe the various network communications standards

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Communications What are computer communications? 

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

p. 460 Fig. 9-1

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Communications What is needed for successful communications? Sending device — initiates instruction to transmit data, instructions, or information

Communications device — connects the sending device to the communications channel

Communications device — connects the communications channel to the receiving device

p. 460 - 461

Communications channel — media on which data, instructions, or information travel

Receiving device — accepts transmission of data, instructions, or information

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Uses of Computer Communications What are some uses of communications technology?

Internet

Chat Rooms

FTP

p. 462

Web

Instant Messaging

E-Mail

Newsgroups Web Folders

Internet Telephony

Video Conferencing

Fax Machine or Computer Fax/Modem

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Uses of Computer Communications What are wireless messaging services? Text messaging Wireless instant allows users to send messaging allows and receive short wireless mobile text messages on a devices to exchange smart phone or messages Picture messaging PDA allows users to send graphics, pictures, video clips, sound files, and short text messages p. 463 - 464

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Uses of Computer Communications What are public Internet access points and cybercafés? 



Public Internet access point allows wireless connection to Internet in public location Cybercafé is coffee house that provides computers with Internet access

Click to view Web Link, click Chapter 9, Click Web Link from left navigation, then click Hot Spots below Chapter 9 p. 464 Fig. 9-5

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Uses of Computer Communications What is a global positioning system (GPS)? 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 Web Link, click Chapter 9, Click Web Link from left navigation, then click GPS below Chapter 9 p. 466 Fig. 9-6

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Uses of Computer Communications What are collaboration and groupware? 

Collaboration is working with other users connected to a server 



Microsoft’s NetMeeting allows collaboration

Groupware is software that allows people to share information

p. 467 - 468 Fig. 9-7

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Uses of Computer Communications What are voice mail and web services?  

Voice mail is voice message converted to digital form Web services describe standardized software that enables programmers to create applications that communicate with other remote computers over the Internet

p. 468 Fig. 9-8

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Networks What is a network? 

Collection of computers and devices connected via communications devices and transmission media

p. 469 Fig. 9-9

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Networks What is a local area network (LAN)? 

Network in limited geographical area such as home or office building  Wireless LAN (WLAN)  Metropolitan area network (MAN) connects LANs in city or town

Click to view Web Link, click Chapter 9, Click Web Link from left navigation, then click Local Area Networks below Chapter 9 p. 471 Fig. 9-10

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Networks What is a wide area network (WAN)? 



Network that covers large geographic area using many types of media Internet is world’s largest WAN

p. 472 Fig. 9-12

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Networks What is a client/server network? 

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

p. 472 Fig. 9-13

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Networks What is a peer-to-peer network? 



Simple network that connects fewer than 10 computers Each computer, or peer, has equal capabilities

p. 473 Fig. 9-14

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Networks What is Internet peer-to-peer (P2P)?  Enables users to connect to each other’s hard disks and exchange files directly

Click to view Web Link, click Chapter 9, Click Web Link from left navigation, then click P2P below Chapter 9 p. 473 Fig. 9-15

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Networks What is a bus network? 



All computers and devices connect to central cable, or bus Example of network topology (layout of devices in network) 

p. 474 Fig. 9-16

Popular topologies are bus, ring, and star

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Networks What is a ring network? 



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

p. 474 Fig. 9-17

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Networks What is a star network? 



All devices connect to a central device, called hub All data transferred from one computer to another passes through hub

p. 475 Fig. 9-18

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Networks What is an intranet? Internal network that uses Internet technologies

Makes information accessible to employees

Typically includes connection to Internet Extranet allows customers or suppliers to access part of company’s intranet

p. 475

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Network Communications Standards What are Ethernet and token ring? 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

Click to view Web Link, click Chapter 9, Click Web Link from left navigation, then click Ethernet below Chapter 9 p. 476

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

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Network Communications Standards What are TCP/IP and 802.11? 

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

p. 477 - 478 Fig. 9-20

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Network Communications Standards What is Bluetooth? 

p. 478

Short-range radio waves transmit data between Bluetooth devices

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Network Communications Standards What are IrDA, RFID, and Wireless Applications Protocol (WAP)? Radio Frequency Identification (RFID) IrDA specification allows data to be transferred wirelessly via infrared light waves

uses radio signals to communicate with a tag placed in an object

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

Click to view Web Link, click Chapter 9, Click Web Link from left navigation, then click WAP below Chapter 9 p. 478 - 480

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Communications Software What is communications software? Programs that help users establish connection to Internet, other network, or another computer

Programs that help users manage transmission of data, instructions, and information Programs that provide an interface for users to communicate with one another

p. 480

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Communications Over the Telephone Network What is the public switched telephone network (PSTN)? 

Worldwide telephone system that handles voice-oriented telephone calls

p. 481 Fig. 9-23

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Communications Over the Telephone Network What is a dial-up line? 

Temporary connection using telephone line for communications  

p. 481

Costs no more than making regular call Computers at any two locations can establish a connection using modems and telephone network Next

Communications Over the Telephone Network What is a dedicated line? Always-on connection between two communications devices





Four types are ISDN line, DSL, T-carrier line, and ATM

Click to view Web Link, click Chapter 9, Click Web Link from left navigation, then click DSL below Chapter 9 p. 482 Fig. 9-24

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Communications Devices What are examples of communications devices? Common types are dial-up modems, ISDN and DSL modems, cable modems, network cards, wireless access points, routers, and hubs ISDN and DSL modems send and receive data from ISDN and DSL lines

p. 484

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Communications Devices What is a dial-up modem?  

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

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

p. 485 Figs. 9-27

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Communications Devices What are ISDN and DSL modems? 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

p. 485

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Communications Devices What is a cable modem? 





Sends and receives data over cable television network Much faster than dial-up modem or ISDN Sometimes called a broadband modem

p. 485 - 486 Fig. 9-28

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Communications Devices What is a wireless modem? 



Allows access to the Web wirelessly from a notebook computer, a PDA, a smart phone, or other mobile device Typically use the same waves used by cellular telephones

p. 486 Fig. 9-29

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Communications Devices What is a network card? 



Adapter card, PC Card, or compact flash card that enables computer or device to access network Sometimes called network interface card (NIC)

p. 486 Fig. 9-30

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Communications Devices What is a wireless access point? 

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

p. 487 Fig. 9-31

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Communications Devices What is a router? 



Connects computers and transmits data to correct destination on network Routers forward data on Internet using fastest available path

Click to view Web Link, click Chapter 9, Click Web Link from left navigation, then click Hardware Firewalls below Chapter 9 p. 488 Fig. 9-32

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Communications Devices What is a hub? 

Device that provides central point for cables in network

p. 488 Fig. 9-33

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Home Networks What is a home network?  

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

Click to view Web Link, click Chapter 9, Click Web Link from left navigation, then click Home Networks below Chapter 9 p. 489 Fig. 9-34

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Communications Channel What is a communications channel? 

Transmission media on which data travels in communications system Transmission media are materials capable of carrying one or more signals

p. 491

Bandwidth is amount of data that can travel over channel

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

p. 491 Fig. 9-35

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Physical Transmission Media What is physical transmission media? 

Wire, cable, and other tangible materials used to send communications signals

p. 492 Fig. 9-36

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Physical Transmission Media What are twisted-pair cable and coaxial cable?  

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

p. 493 Fig. 9-37—9-38

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Physical Transmission Media What is fiber-optic cable? 





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)

p. 493 Fig. 9-39

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Wireless Transmission Media What is wireless transmission media?  

Used when inconvenient, impractical, or impossible to install cables Includes Bluetooth and IrDA

p. 494 Fig. 9-40

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Wireless Transmission Media What are broadcast radio and cellular radio? 



Broadcast radio distributes radio signals over long and short distances Cellular radio is form of broadcast radio used for mobile communications

Click to view Web Link, click Chapter 9, Click Web Link from left navigation, then click Cellular Communications below Chapter 9 p. 494 Fig. 9-41

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Wireless Transmission Media What is a microwave station? 



Earth-based reflective dish used for microwave communications Must transmit in straight line with no obstructions

p. 495 Fig. 9-42

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Wireless Transmission Media What is a communications satellite? 

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

p. 496 Fig. 9-43

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Summary of Communications and Networks

Communications terminology and applications Various communications devices, media, and procedures How to join computers into a network

Chapter 9 Complete