1	Chapter 9
2	Topics Linking Up: Network Basics Electronic Mail, Teleconferences, and Instant Messages: Interpersonal Computing Converging Communication Technologies: From Messages to Money
3	Linking Up: Network Basics A computer network is any system of two or more computers that are linked together. How do networks impact systems? People share computer hardware, thus reducing costs People share data and software programs, thus increasing efficiency and production People work together in ways that are otherwise difficult or impossible
4	Basic Network Anatomy The three basic components of a network: Hardware Software People Direct Connection--one of many computers linked in an office Remote Access--computer linked to a network through a phone line, television cable system or satellite link
5	The Network Interface A network interface card (NIC) permits direct network connection It adds an additional serial port to the computer The network interface card controls the flow of data between the computer’s RAM and the network cable.
6	Communication á la Modem A modem is a hardware device that connects a computer’s serial port to a telephone line (for remote access). May be internal on the system board or external modem sitting in a box linked to a serial port. Modem transmission speed is measured in bits per second (bps) and generally transmit at 28,000 bps to 56.6K bps
7	Conversion of Signals
8	Conversion of Signals
9	Networks Near and Far Local-area network (LAN) Computers are linked within a building or cluster of buildings. Each computer and peripheral is an individual node on the network. Nodes are connected by cables which may be either twisted pair (copper wires) or coaxial cable.
10	Networks Near and Far Wide-area network (WAN) A network that extends over a long distance. Each network site is a node on the network. Data transmitted over common pathways called a backbone.
11	Wide-Area Networks Made up of LANs linked by phone lines, microwave towers, and communication satellites. Bridges, routers, and gateways are hardware devices that pass messages between networks.
12	Communication Software Protocol - set of rules for the exchange of data between a terminal and a computer or between two computers Communication software establishes a protocol that is followed by the computer’s hardware
13	Communication Software Many forms: Network operating system (NOS) - handles communications between many workstations Client/server model - one or more computers act as dedicated serves and all the remaining computers act as clients Peer-to-peer model - every computer on the network is both client and server Many networks are hybrids, using features of the client/server and peer-to-peer models
14	Client/Server Model
15	The Network Advantage Why do people use networks? To share computer resources (hardware and software) To support working together in new and different ways
16	E-mail Mail, Teleconferences, and IM: Interpersonal Computing Electronic mail, teleconferencing and instant messaging allow communications between two or more people. Meetings can be held in real-time (synchronous) or delayed (asynchronous) Chat rooms are examples of synchronous communications; bulletin boards are examples of asynchronous communications.
17	The Postal Alternative E-mail is fast. E-mail doesn’t depend on location. E-mail facilitates group communication. E-mail messages are digital data that can be edited and combined with other computer-generated documents.
18	Advantages of E-mail and Teleconferencing On-line communication is less intrusive. On-line communication allows time shifting. Teleconferences and e-mail promotes teleworking. Teleconferences and e-mail emphasize the message over the messenger.
19	On-line Issues for E-mail and Teleconferencing Vulnerable to machine failures, network glitches, human errors and security Threat to privacy E-mail forgery Information overload Missing “human” elements of communication
20	Rules of Thumb: On-line Survival Tips If you don’t have to be on line, go off line. Avoid peak hours Let your system do as much of the work as possible. Store names and addresses in an on-line address book Protect your privacy Cross-check on-line information sources Be aware and awake Avoid information overload.
21	Converging Communication Technologies: From Messages to Money On-line Information Services Fax Machines and Fax Modem Voice Mail and Computer Telephony Global Positioning System Video Teleconferencing E-Money
22	Physical Media for Networks Networks are built on physical media. Twisted pair (Category 5) Twisted pair (Traditional) Coaxial Cable Fiber optic Wireless/infrared Wireless/radio What affects network performance? Bandwidth and maximum operating distance
23	Bandwidth The amount of information that can be transmitted in a given amount of time Impacted by: Physical media that make up the network Amount of network traffic Software protocols of the network Type of network connection
24	Fiber Optic Cables Fiber optic cables are replacing aging cooper lines with high-capacity fiber optic cables. They use light waves to carry information at blinding speeds. A single fiber optic cable can transmit half a gigabit (500 million bits) per second, replacing 10,000 standard telephone cables. Data is transmitted more accurately and reliably.
25	Digital Communication Comes Home Digital communication lines will radically change services to our homes. Multi-person video phone conversations, universal e-mail, customized digital newspapers, automatic utility metering and unlimited entertainment options
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