cs/is 465: data communication and networks 1 cs/is 465 data communications and networks lecture 28...

CS/IS 465: Data Communication and Networks

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CS/IS 465Data Communications and Networks

Lecture 28

Martin van Bommel


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High-Speed & Wireless LANs• Why?

– Extraordinary growth in speed, power, and storage capacity of PCs

– Increasing use of LANs as computing platforms

– Low speed not capable of supporting requirements

• Examples– Server farms - multiple centralized servers

– Power work groups - e.g. CAD company

– High-speed backbones


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LAN Generations

• First - CSMA/CD and Token Ring– terminal-to-host connnectivity– client-server at moderate data rates

• Second - FDDI and others– backbone LANs and high-performance stations

• Third - ATM LANs– multiple guaranteed high-speed classes of service– multimedia applications


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Fast Ethernet

• CSMA/CD operating at 100 Mbps

• Easy to integrate with existing systems

• 100BASE-X - two simplex links b/w nodes

• Can use UTP (100BASE-TX) but requires two lines between stations

• Can use Fiber (100BASE-FX)


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Fast Ethernet Configuration

• 100BASE-T uses star-wire topology

• All stations connected to central point using multiport repeater (broadcast method)

• Repeater, not stations, detects collisions and sends jam signal on all ports

• Repeaters connected with bridges


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Fast Ethernet Full-duplex Mode

• Traditional Ethernet is half-duplex

• Two links b/w stations allows full-duplex

• NICs must support full-duplex mode

• Switched hub must be used - determines path for frame

• No collisions ever occur


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Mixed Ethernet

• Can mix 10-Mbps and 100-Mbps LANs

• Slow stations attach to 10-Mbps hubs

• Hubs connected to 100-Mbps hubs

• High-speed servers connected to 100-Mbps

• See Figure 15.4


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Gigabit Ethernet

• Still under development (started late 1995)

• Retains CSMA/CD protocol and Ethernet format, ensuring smooth upgrade path

• Uses optical fiber over short distances

• 1-Gbps switching hub provides backbone connectivity for central servers and high-speed workgroup hubs - Figure 10-5


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FDDI

• Fiber Distributed Data Interface

• Oldest high-speed LAN standard

• Token ring MAC protocol with early token release (frame occupies only small part of ring with high-speed)

• Piggy-back frames by claiming early-release token


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FDDI (2)

• 100 Mbps optical fiber

• 100 Mbps category 5 UTP or STP

• Respectable market share

• ATM LANs better suited to multimedia traffic and to integrate with ATM WANs


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ATM LANs• Several types

– Gateway to ATM WAN • ATM switch acts as router to ATM WAN

– Backbone ATM switch• ATM switch(es) interconnect other LANs

– Workgroup ATM• high-performance stations connect directly to ATM

switch

– Mixture of types on internet


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Backbone ATM LAN• Local ATM network consists of switches

interconneted with high-speed point-to-point links running ATM rates of 155 & 622 Mbps

• LANs directly connect to ATM switches

• ATM switch performs buffering, speed and protocol conversion

• Figure

• End systems still limited by shared mediums


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ATM Hub

• Each ATM hub includes number of ports

• Ports operate at different rates and protocols

• Each end system has dedicated point-to-point link with hub - Figure

• Existing LAN hardware can be used on LAN systems while introducing ATM LAN

• Hub requires complex protocol conversions


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Pure ATM LAN

• End systems attach directly to ATM network

• ATM protocols implemented

• No conversions required


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ATM Compatibility Issues

• Interaction between ATM-based station and legacy-based station

• Interaction between two stations using same legacy protocol but communicating via ATM

• Interaction between two stations using different legacy protocols via ATM

• Solution - bridge or router type ATM switch

cs/is 465: data communication and networks 1 cs/is 465 data communications and networks lecture 28...

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