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Chapter 9
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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