Chapter 8 Communications and Networks

Communications

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

Sending device — initiates

instruction to transmit data, instructions, or

information

Successful Communications—5 components

Communications device — connects the communications

channel to the receiving device

Receiving device — accepts

transmission of data, instructions, or

information

Communications device — connects

the sending device to the communications

channel

Communications channel — media

on which data, instructions, or

information travel

Types of Networks Collection of computers and devices connected via communications devices and transmission

media

Local Area Network (LAN) Network in limited geographical area—office building

Metropolitan area network (MAN)—covers city Wide area network (WAN)

Potentially world-wide coverage Internet is the largest WAN

Types of Networks

Client/Server Peer to PeerSimple network that connects fewer than 10 computersEach computer has equal capabilities

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

Types of Networks

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

Restricted network usually within an organizationAllows sharing of organizational-related info without putting it out for public reading

Nextp. 292 Fig. 8-11

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

Networks Topology

Layout of devices in a networkBus network

All computers and devices connect to a central cable, or bus

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

Networks Topology

Star network

Nextp. 293 Fig. 8-14

All devices connect to a central device, called hub

All data transferred from one computer to another passes through hub

Ethernet and Token Ring Technology

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

TCP/IP and 802.11 BlueToothShort-range radio waves transmitdata between Bluetooth devices

Nextp. 294

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

p. 294

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

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 Devices

What are examples of communications devices?

Nextp. 298

Common types are dial-up modems, ISDN and DSL modems, cable modems, network cards,

wireless access points, and routers

ISDN and DSL modems send and receive data from ISDN

and DSL lines

Using the Telephone System to Communicate

Public switched telephone network (PSTN)?

Dial-up lineTemporary connection using telephone line for communications

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

Communications Devices

What is a cable modem?

Nextp. 300 Fig. 8-19

Sends and receives data over cable television network

Much faster than dial-up modem or ISDN

Sometimes called a broadband modem

Communications Devices

What is a network card?

Nextp. 300 Fig. 8-20

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

Communications Devices

What are ISDN and DSL modems?

Nextp. 300

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 wireless access point?

Nextp. 301 Fig. 8-21

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

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

Allow messages to flow between networks

Firewalls

Program or hardware device that filters information coming from Internet connection

If packet of info is flagged, not allowed through

Communications Channel

What is a channel?

Nextp. 303

Transmission media on which data travels in communications system Wire, cable, and other tangible materials used

to send communications signals

Bandwidth is amount of data that can travel over channel

Transmission media are materials capable of carrying one or more signals

Communications Channel

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

Nextp. 304 Fig. 8-24

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. 305 Fig. 8-25—8-26

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. 306 Fig. 8-27

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 wireless transmission media?

Nextp. 306

Used when inconvenient, impractical, or impossible to install cables

Includes infrared, broadcast radio, cellular radio, microwaves, and communications satellites

Internet Telephony

p. 285 Next

Internet telephonyInternet telephony transmission of phone calls over

data networkSometimes called

Voice over IPVoice over IP

Uses of Computer Communications

What are voice mail and wireless messaging services?

Nextp. 289 Fig. 8-7

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

Text Messaging Instant Messaging Picture Messaging

Collaboration and Groupware

What are collaboration and groupware?

Next

Microsoft Office 2003allows collaboration

Groupware is softwarethat allows peopleto shareinformation

Collaboration is working with other users connected to a server

Public Access Points

Next

Public Internet access point allows wireless connection to Internet in public location

Hot spot

Global Positioning System

Next

Verichip (December, 2001)

Implantable Personal Verification SystemUses RFIDSize of a TicTacImplanted under the skinImmediate ID and retrieval of subscriber supplied registry info