Chapter 08 Notes

CommunicationsComputer communications describes a process in which two or more computers or devices transfer data, instructions, and information*Page 460

CommunicationsA sending device that initiates an instruction to transmit data, instructions or information.A communication channel or transmission media on which the data , instructions or information travel.A receiving device that accepts the transmission of data, instruction or information.*

Uses of Computer CommunicationsBlogsChat roomsE-mailFaxFTPInstant MessagingInternet

NewsgroupsRSSVideo ConferencingVoIPWebWeb 2.0Wikis

Discovering Computers 2012: Chapter 9*

Discovering Computers 2012: Chapter 9

Uses of Computer CommunicationsChat rooms : Real-time type conversation among two or more people that takes place on computer connected to networkE-mail : Transmission of messages and file via computer networkFax : Transmits and receives documents over telephone linesInternet : Worldwide collection of networks that links million of business, government agencies ,educational institutes and individualsWikis : Collaborative websites that allow users to create , add , modify or delete website content.Web :Web 2.0 :

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Difference between :WEBWEB 2.0*

Uses of Computer CommunicationsWireless Internet access points allow people to connect wirelessly to the Internet from home, work, school, and in many public locationsTwo Types:Hotspots : It is a wireless network that provides Internet connections to mobile computers and devicesWi-Fi Wi-MAX Bluetooth Mobile wireless networks *Pages 464 465 Figure 9-4

Uses of Computer CommunicationsA global positioning system (GPS) is a navigation system that consists of one or more earth-based receivers that accept and analyze signals sent by satellites in order to determine the GPS receivers geographic locationGPS receivers are:*Page 466

Uses of Computer CommunicationsDiscovering Computers 2012: Chapter 9*Page 467


Uses of Computer CommunicationsMany programs provide a means to collaborate, or work online, with other users connected to a serverCollaboration software includes tools that enable users to share documents via online meetings and communicate with other connected usersOnline meetings : allows users to share documents with other in real timeWeb conferences: when online meetings takes place on the webDocument management systems : Provides for storage and management of a companys documents such as presentations etc.

*Page 468

Uses of Computer CommunicationsWeb services enable programmers to create applications that communicate with other remote computers over the Internet or on an internal business networkA mashup is a Web application that combines services from two or more sources*Page 469 Figure 9-8

Outlines for NETWORKNetwork - definitionAdvantages of Network facilitating communication Sharing hardware Sharing data and information sharing software transferring funds Different types of networkLANWLAN MAN WANNetwork Architecture Client/server Peer-to-PeerInternet Peer to Peer

*Network topologyStar Network Bus Network Ring Network

Communication Standard Ethernet Token RingTCP/IPWi-FiBluetoothWAPUWBIrDARFIDWi-MAX

NetworksA network is a collection of computers and devices connected together via communications devices and transmission mediaAdvantages of a network include:*Pages 470 - 471

Advantages of a networkFacilitating communications : Using a network people communicates efficiently and easily via email , instant messaging , chat rooms, blogs , online social networks etc.Sharing hardware : In a networked environment, each computer on the network can have access to hardware on the network.Sharing Data & Info : In a networked environment , any authorized computer user can access data and information stored on other computers on the network.Sharing Software : Users connected to a network have access to software on the network.Transferring funds :Called Electronic Funds Transfer (EFT) , it allows users connected to a network to transfer money from one bank account to another via transmission media.*

NetworksA local area network (LAN) is a network that connects computers and devices in a limited geographical area such as a home , school computer lab or office building.A wireless LAN (WLAN) is a LAN that uses no physical wires. Computers and devices that access a wireless LAN must have built in wireless capabilities .

*Page 472 Figures 9-10 9-11

NetworksA metropolitan area network (MAN) is a high speed network that connects local area networks in a metropolitan area such as a city or a town and handles bulk of communication across region.A wide area network (WAN) is a network that covers a large geographical area such as city or country using a communications channel that combines many types of media such as telephone lines and cables.*Page 473 Figure 9-12

Networks- NETWORK ARCHITECTURES :

The design of computers, devices, and media on a network is sometimes called the network architecture and is categorized as :Client /Server: one or more computers act as a server and the other computers on the network request services from the server Clients are other computers and mobile devices on the network that rely on the server for its resources.Peer to Peer : One type of peer to peer network is a simple network that typically connects less than 10 computers. Each computer , called a Peer, has equal responsibilities and capabilities, sharing hardware with other computers on peer to peer.*

NetworksInternet Peer to Peer : also called P2P , describes an Internet network on which users access each others hard disks and exchange files directly over the Internet*Page 475 Figure 9-15

Networks - Network Topology A network topology refers to the layout of the computers and devices in a communications networkStar Network : On a star network, all computers and devices on the network connect to a central device, thus forming a starBus Network : it consists of single central cable to which all computers and other devices connect.Ring Network : a cable forms a closed loop with all computers and devices arranged along the ring.*

NetworksDiscovering Computers 2012: Chapter 9*Page 477


Network Communications StandardsIEEE propose, develop and approve network standardsNetwork standard define guidelines that specify the way computers access the medium to which they are attached, the type of medium used, speeds used, physical cable and wireless technology used.*

Network Communications StandardsDiscovering Computers 2012: Chapter 9*Page 477


Network Communications StandardsEthernet is a network standard that specifies no central computer should control when data can be transmittedThe token ring standard specifies that computers and devices on the network share a special signal (token)TCP/IP is a network standard that defines how messages are routed from one end of a network to another

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Network Communications StandardsWi-Fi identifies any network based on the 802.11 standard that facilitates wireless communication*Page 479 Figure 9-20

Network Communications StandardsBluetooth defines how two Bluetooth devices use short-range radio waves to transmit dataUWB (ultra-wideband) specifies how two UWB devices use short-range radio waves to communicate at high speedsIrDA transmits data wirelessly via infrared light wavesRFID uses radio signals to communicate with a tag placed in or attached to an object, animal, or person*Pages 480 - 481

Network Communications Standards*Page 482

Communications SoftwareCommunications software consists of programs that:Help users to establish a connection to another computer or networkManage the transmission of data, instructions, and informationProvide an interface for users to communicate with one another

*Page 482

Communications DevicesA communications device is any type of hardware capable of transmitting data, instructions, and information between a sending device and a receiving deviceA Dial-up modem converts signals between analog and digitalDigital modem sends and receives data and information to and from a digital lineISDN DSL Cable

*Page 485

Communications Devices3. A wireless modem uses the cell phone network to connect to the Internet wirelessly from a notebook computer, a smart phone, or other mobile device*Page 487 Figure 9-28

Communications Devices4. A network card which is also known as Network Interface Card enables a computer or device to access a network. Network cards are available in a variety of styles. Wireless network cards often have an antenna that provides wireless data transmission*

Communications Devices5. A wireless access point is a central communications device that allows computers and devices to transfer data wirelessly among themselves or to a wired network*Page 487 Figure 9-30

Communications Devices6. A router connects multiple computers or other routers together and transmits data to its correct destination on a networkMany are protected by a hardware firewall*Page 488 Figure 9-31

Communications Devices7. A hub or switch connects several devices in a network together and receives data from many directions and then forwards it to one or more directions.*

Home Networks*Page 489Home networks provide computers with the following capabilities:Connect to the Internet at the same timeConnect game consoles to the InternetPlay multiplayer gamesShare a single high-speed Internet connectionShare peripheralsAccess files and programs on other computersSubscribe to and use VoIP

Home NetworksTypes of wired home networks:Ethernet requires that each computer have built-in network capabilities which connects to a central network hub.Power line cable uses the same line that brings electricity into the house; One end in the USB port and other end in the wall outletPhone line cable easy to install and inexpensive.; one end to an adapter or PC card and other end plugs in a wall telephone jack.

*Page 489

Communications ChannelThe amount of data that can travel over a communications channel sometimes is called the BandwidthLatency is the time it takes a signal to travel from one location to another on a networkTransmission media consists of material capable of carrying one or more signals.Broadband media transmit multiple signals simultaneously.

*Page 491 Figure 9-34

Physical and Wireless Transmission Media*Page 492 Figure 9-35

Physical and Wireless Transmission Media

Physical Transmission MediaTwisted Pair Cable consists of one or more twisted pair wires bundled togetherCoaxial Cable consists of single copper wire surrounded by at least three layers : an insulating material,a woven metal , and a plastic outer coating Fiber Optic Cable consists of thin strands of glass or plastic that use light to transmit signals.*

Physical Transmission Media*

Wireless Transmission MediaCellular radio is a form of broadcast radio that is used widely for mobile communicationsBroadcast radio distributes radio signals through air over long and short distances.Microwaves are radio waves that provide a high-speed signal transmissionA communications satellite is a space station that receives microwave signals from an earth-based station, amplifies it, and broadcasts the signal over a wide area

*Pages 494 - 495 Figure 9-40

Wireless Transmission Media*Page 494 Figure 9-39

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Chapter 08 Notes