Chapter 18

Virtual-Circuit Networks:Frame Relay and ATM

18.1 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

1818--1 1 FRAME RELAYFRAME RELAY

FrameFrame RelayRelay isis aa virtualvirtual circuitcircuit widewide areaarea networknetworkFrameFrame RelayRelay isis aa virtualvirtual--circuitcircuit widewide--areaarea networknetworkthatthat waswas designeddesigned inin responseresponse toto demandsdemands forfor aa newnewtypetype ofof WANWAN inin thethe latelate 19801980ss andand earlyearly 19901990sstypetype ofof WANWAN inin thethe latelate 19801980ss andand earlyearly 19901990ss..

ArchitectureTopics discussed in this section:Topics discussed in this section:

Frame Relay LayersExtended AddressFRADFRADsVOFRLMI

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LMI

Figure 18.1 Frame Relay network

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Note

VCIs in Frame Relay are called DLCIs.

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Figure 18.2 Frame Relay layers

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Note

Frame Relay operates only at the h i l d d t li k lphysical and data link layers.

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Figure 18.3 Frame Relay frame

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Note

Frame Relay does not provide flow or t l th t b id derror control; they must be provided

by the upper-layer protocols.

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Figure 18.4 Three address formats

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Figure 18.5 FRAD

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1818--2 2 ATMATM

A hA h T fT f M dM d (ATM)(ATM) ii thth llll llAsynchronousAsynchronous TransferTransfer ModeMode (ATM)(ATM) isis thethe cellcell relayrelayprotocolprotocol designeddesigned byby thethe ATMATM ForumForum andand adoptedadopted bybythth ITUITU TTthethe ITUITU--TT..

Topics discussed in this section:Topics discussed in this section:Design GoalsProblems

pp

ArchitectureSwitchingATM Layers

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ATM Layers

Figure 18.6 Multiplexing using different frame sizes

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A ll t k th ll th b i

Note

A cell network uses the cell as the basic unit of data exchange.

A cell is defined as a small, fixed-size block of information.b oc o o at o

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Figure 18.7 Multiplexing using cells

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Figure 18.8 ATM multiplexing

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Figure 18.9 Architecture of an ATM network

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Figure 18.10 TP, VPs, and VCs

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Figure 18.11 Example of VPs and VCs

18.18

Note

Note that a virtual connection is defined b i f bby a pair of numbers: the VPI and the VCI.

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Figure 18.12 Connection identifiers

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Figure 18.13 Virtual connection identifiers in UNIs and NNIs

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Figure 18.14 An ATM cell

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Figure 18.15 Routing with a switch

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Figure 18.16 ATM layers

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Figure 18.17 ATM layers in endpoint devices and switches

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Figure 18.18 ATM layer

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Figure 18.19 ATM headers

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Figure 18.20 AAL1

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Figure 18.21 AAL2

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Figure 18.22 AAL3/4

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Figure 18.23 AAL5

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1818--3 3 ATM LANsATM LANs

ATMATM isis mainlymainly aa widewide--areaarea networknetwork (WAN(WAN ATM)ATM);;however,however, thethe technologytechnology cancan bebe adaptedadapted toto locallocal--areaarea

kk (A(A A )A ) hh hi hhi h dd ff hhnetworksnetworks (ATM(ATM LANs)LANs).. TheThe highhigh datadata raterate ofof thethetechnologytechnology hashas attractedattracted thethe attentionattention ofof designersdesigners

hh l kil ki ff dd dd iiwhowho areare lookinglooking forfor greatergreater andand greatergreater speedsspeeds ininLANsLANs..

ATM LAN ArchitectureTopics discussed in this section:Topics discussed in this section:

LAN Emulation (LANE)Client/Server Model

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Mixed Architecture with Client/Server

Figure 18.24 ATM LANs

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Figure 18.25 Pure ATM LAN

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Figure 18.26 Legacy ATM LAN

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Figure 18.27 Mixed architecture ATM LAN

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Figure 18.28 Client and servers in a LANE

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Figure 18.29 Client and servers in a LANE

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