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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 © MMII JW Ryder CS 428 Computer Networks
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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 © MMII JW Ryder CS 428 Computer Networks
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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 CS 428 Computer Networks
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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 © MMII JW Ryder CS 428 Computer Networks
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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 © MMII JW Ryder CS 428 Computer Networks
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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 CS 428 Computer Networks
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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 CS 428 Computer Networks
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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 CS 428 Computer Networks
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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 CS 428 Computer Networks
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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 © MMII JW Ryder CS 428 Computer Networks
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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 © MMII JW Ryder CS 428 Computer Networks
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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 © MMII JW Ryder CS 428 Computer Networks
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