Approaches To Network Communications

Approaches to Network Communications • Circuit-Switched – Connection Oriented – Form dedicated connection between 2 points – U.S. Telephone System

• Packet_Switched – – – – –

Connectionless Data to be transferred broken into small packets Multiplexed onto high capacity systems Carries a few hundred(s) data usually Advantage: Multiple communications occur concurrently – Disadvantage: Network overload causes throughput decrease

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WAN/LAN • Fundamental difference between large and small spanning geographical distance networks • 2 Categories, no formal split • Wide Area Networks, long haul networks – Slower speeds, greater delays – Typical speeds 56Kbps to 155 Mbps

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WAN/LAN • Local Area Network – Highest speed, sacrifice long distance – Single building, small campus – Typical speeds 10 Mbps to 2 Gbps

• LAN - Each computer connects directly to physical transport medium via network interface device © MMII JW Ryder

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WAN/LAN • WAN - Network usually consists of a series of interconnected intermediate node routers interconnected by communication lines and modems • Extending network means adding another packet switch • Connect a new computer to WAN means connecting it to a packet switch

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WAN/LAN • Adding a new switch adds delay along route • Software hides details of hardware on different packet switches – Hardware independent transport

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Network Hardware Addresses • Each hardware technology has an addressing mechanism • Specifies destination of packet • Every computer on a network is assigned a unique address – Usually an integer

• Destination address field contained in each packet – Same location in all packets

• Sender must know destination address © MMII JW Ryder

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Ethernet Technology • Packet-switched LAN technology – Xerox Palo Alto Research Center (PARC) in early ‘70s

• See Figure 2.1 on page 20 • Connection between computer and co-axial (coax) called a transceiver • See Figure 2.2 on page 21 • Pin hole in ether = tap • Connections to Ethernet have 2 major components © MMII JW Ryder

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Transceiver/Host Interface • Host Adapter • Transceiver – Connects to center wire and braided shield – Sensing and sending signals on the ether

• Host Interface – Plugs into the computer’s bus on motherboard – Connected to transceiver by cable called Attachment Unit Interface (AUI)

• Oldest form of Ethernet technology (Thick-Wire Ethernet) • See Figure 2.4 on page 23 © MMII JW Ryder

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Thin-Wire Ethernet • First improvement, better access, lower cost • Thinnet • Thinner coax cable, less expensive, more flexible • Thinner cable more susceptible to electronic interference (noise), shorter distances, fewer computers © MMII JW Ryder

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Thinnet • Replace high cost transceivers with digital circuitry inside of host interfaces • Direct connection from computer to ether • Connects direction from one computer to another • See Figure 2.5 on page 24 • BNC Connectors, T’s in the back plugged into host adapter – Show on board

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Twisted Pair Ethernet • No longer need for shield of coax • Ethernet access with pair of unshielded copper wires similar to telephone wires • Further reduces cost, protects other users on network when someone disconnects • 10Base-T wiring connects computers via an Ethernet Hub • See Figure 2.6 on page 25

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Hub • Electronic device that simulates signals of Ethernet • Computers must be < 100m away • Requires power • Intelligent vs. Dumb Hub • Connection to hub acts same as host adapter to transceiver

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