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UNIT I (Contd..)UNIT I (Contd..)

High-Speed LANsHigh-Speed LANs

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Introduction Introduction

Fast Ethernet and Gigabit EthernetFast Ethernet and Gigabit Ethernet Fibre ChannelFibre Channel High-speed Wireless LANsHigh-speed Wireless LANs

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Table 6.1Table 6.1

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Emergence of High-Speed Emergence of High-Speed LANsLANs

2 Significant trends2 Significant trends Computing power of PCs continues to Computing power of PCs continues to

grow rapidlygrow rapidly Network computingNetwork computing

Examples of requirementsExamples of requirements Centralized server farmsCentralized server farms Power workgroupsPower workgroups High-speed local backboneHigh-speed local backbone

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Classical EthernetClassical Ethernet

Bus topology LANBus topology LAN 10 Mbps10 Mbps CSMA/CD medium access control CSMA/CD medium access control

protocolprotocol 2 problems:2 problems:

A transmission from any station can be A transmission from any station can be received by all stationsreceived by all stations

How to regulate transmissionHow to regulate transmission

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Solution to First ProblemSolution to First Problem

Data transmitted in blocks called Data transmitted in blocks called frames:frames: User dataUser data Frame header containing unique Frame header containing unique

address of destination stationaddress of destination station

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Figure 6.1Figure 6.1

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CSMA/CDCSMA/CD

Carrier Sense Multiple Access/ Carrier DetectionCarrier Sense Multiple Access/ Carrier Detection

1.1. If the medium is idle, transmit.If the medium is idle, transmit.2.2. If the medium is busy, continue to listen If the medium is busy, continue to listen

until the channel is idle, then transmit until the channel is idle, then transmit immediately.immediately.

3.3. If a collision is detected during If a collision is detected during transmission, immediately cease transmission, immediately cease transmitting.transmitting.

4.4. After a collision, wait a random amount After a collision, wait a random amount of time, then attempt to transmit again of time, then attempt to transmit again (repeat from step 1).(repeat from step 1).

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Figure 6.2Figure 6.2

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Figure 6.3Figure 6.3

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Medium Options at Medium Options at 10Mbps10Mbps

<data rate> <signaling method> <max <data rate> <signaling method> <max length>length>

10Base510Base5 10 Mbps10 Mbps 50-ohm coaxial cable bus50-ohm coaxial cable bus Maximum segment length 500 metersMaximum segment length 500 meters

10Base-T10Base-T Twisted pair, maximum length 100 metersTwisted pair, maximum length 100 meters Star topology (hub or multipoint repeater at Star topology (hub or multipoint repeater at

central point)central point)

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Figure 6.4Figure 6.4

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Hubs and SwitchesHubs and Switches

HubHub Transmission from a station received by Transmission from a station received by

central hub and retransmitted on all central hub and retransmitted on all outgoing linesoutgoing lines

Only one transmission at a timeOnly one transmission at a time

Layer 2 SwitchLayer 2 Switch Incoming frame switched to one outgoing Incoming frame switched to one outgoing

lineline Many transmissions at same timeMany transmissions at same time

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Figure 6.5Figure 6.5

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BridgeBridge Frame handling Frame handling

done in softwaredone in software Analyze and Analyze and

forward one forward one frame at a timeframe at a time

Store-and-Store-and-forwardforward

Layer 2 SwitchLayer 2 Switch Frame handling Frame handling

done in hardwaredone in hardware Multiple data Multiple data

paths and can paths and can handle multiple handle multiple frames at a timeframes at a time

Can do cut-Can do cut-throughthrough

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Layer 2 SwitchesLayer 2 Switches

Flat address spaceFlat address space Broadcast stormBroadcast storm Only one path between any 2 devicesOnly one path between any 2 devices

Solution 1: subnetworks connected Solution 1: subnetworks connected by routersby routers

Solution 2: layer 3 switching, packet-Solution 2: layer 3 switching, packet-forwarding logic in hardwareforwarding logic in hardware

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Figure 6.6Figure 6.6

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Figure 6.7Figure 6.7

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Figure 6.8Figure 6.8

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Figure 6.9Figure 6.9

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Figure 6.10Figure 6.10

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Figure 6.11Figure 6.11

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Benefits of 10 Gbps Benefits of 10 Gbps Ethernet over ATMEthernet over ATM

No expensive, bandwidth consuming No expensive, bandwidth consuming conversion between Ethernet packets conversion between Ethernet packets and ATM cellsand ATM cells

Network is Ethernet, end to endNetwork is Ethernet, end to end IP plus Ethernet offers QoS and traffic IP plus Ethernet offers QoS and traffic

policing capabilities approach that of policing capabilities approach that of ATMATM

Wide variety of standard optical Wide variety of standard optical interfaces for 10 Gbps Ethernetinterfaces for 10 Gbps Ethernet

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Fibre ChannelFibre Channel 2 methods of communication with 2 methods of communication with

processor:processor: I/O channelI/O channel Network communicationsNetwork communications

Fibre channel combines bothFibre channel combines both Simplicity and speed of channel Simplicity and speed of channel

communicationscommunications Flexibility and interconnectivity of Flexibility and interconnectivity of

network communicationsnetwork communications

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Figure 6.12Figure 6.12

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I/O channelI/O channel

Hardware based, high-speed, Hardware based, high-speed, short distanceshort distance

Direct point-to-point or multipoint Direct point-to-point or multipoint communications linkcommunications link

Data type qualifiers for routing Data type qualifiers for routing payloadpayload

Link-level constructs for individual Link-level constructs for individual I/O operationsI/O operations

Protocol specific specifications to Protocol specific specifications to support e.g. SCSIsupport e.g. SCSI

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Fibre Channel Network-Fibre Channel Network-Oriented FacilitiesOriented Facilities

Full multiplexing between multiple Full multiplexing between multiple destinationsdestinations

Peer-to-peer connectivity between Peer-to-peer connectivity between any pair of portsany pair of ports

Internetworking with other Internetworking with other connection technologiesconnection technologies

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Fibre Channel Fibre Channel RequirementsRequirements

Full duplex links with 2 fibres/linkFull duplex links with 2 fibres/link 100 Mbps – 800 Mbps100 Mbps – 800 Mbps Distances up to 10 kmDistances up to 10 km Small connectorsSmall connectors high-capacityhigh-capacity Greater connectivity than existing Greater connectivity than existing

multidrop channelsmultidrop channels Broad availabilityBroad availability Support for multiple cost/performance Support for multiple cost/performance

levelslevels Support for multiple existing interface Support for multiple existing interface

command setscommand sets

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Figure 6.13Figure 6.13

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Fibre Channel Protocol Fibre Channel Protocol ArchitectureArchitecture

FC-0 Physical MediaFC-0 Physical Media FC-1 Transmission ProtocolFC-1 Transmission Protocol FC-2 Framing ProtocolFC-2 Framing Protocol FC-3 Common ServicesFC-3 Common Services FC-4 MappingFC-4 Mapping

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Wireless LAN Wireless LAN RequirementsRequirements

ThroughputThroughput Number of nodesNumber of nodes Connection to backboneConnection to backbone Service areaService area Battery power consumptionBattery power consumption Transmission robustness and securityTransmission robustness and security Collocated network operationCollocated network operation License-free operationLicense-free operation Handoff/roamingHandoff/roaming Dynamic configurationDynamic configuration

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Figure 6.14Figure 6.14

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IEEE 802.11 ServicesIEEE 802.11 Services

Association Association ReassociationReassociation DisassociationDisassociation AuthenticationAuthentication PrivacyPrivacy

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Figure 6.15Figure 6.15

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Figure 6.16Figure 6.16