Computer networks : a systems approach

825 Pages·2003·2.773 MB·English

by  Larry L Peterson, Bruce S Davie

T H I R D E D I T I O N
Larry L. Peterson & Bruce S. Davie
C O M P U T E R
N E T W O R K S
A Systems Approach
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To Lee Peterson and Robert Davie
F O R E W O R D
David Clark
MassachusettsInstituteofTechnology
This third edition represents another major upgrade to this classic networking
book.Thefieldcontinuestochangefast,andnewconceptsemergewithamaz-
ing speed. This version expands its discussion of a lot of important new top-
ics,includingpeer-to-peernetworks,Ipv6,overlayandcontentdistributionnetworks,
MPLS and switching, wireless and mobile technology, and more. It also contains an
earlierandstrongerfocusonapplications,whichreflectsthestudentandprofessional’s
increasedfamiliaritywithawiderangeofnetworkedapplications.Thebookcontinues
itstraditionofgivingyouthefactsyouneedtounderstandtoday’sworld.
But it has not lost track of its larger goal, to tell you not only the facts but the
whybehindthefacts.Thephilosophyofthebookremainsthesame:tobetimelybut
timeless.Whatthisbookwillteachyouintoday’snetworkedworldwillgiveyouthe
insight needed to work in tomorrow’s landscape. And that is important, since there
isnoreasontobelievethattheevolutionofnetworksisgoingtoslowdownanytime
soon.
Itishardtorememberwhattheworldlookedlikeonlytenyearsago.Backthen
the Internet was not really a commercial reality. Ten megabits per second was really
fast.Wedidn’tworryaboutspamandvirusattacks—weleftourcomputersunguarded
andhardlyworried.Thosetimesweresimpler,buttodaymaybemoreexciting.And
youbetterbelievethattomorrowwillbedifferentfromtoday:atleastasexciting,with
lucknolesstrustworthy,andcertainlybigger,fasterandfilledwithfreshinnovation.
SoIhopeLarryandBrucecanrelaxforalittlebeforetheyhavetostartthenext
revision.Meanwhile,usethisbooktolearnabouttodayandgetreadyfortomorrow.
Havefun.
F O R E W O R D T O T H E F I R S T E D I T I O N
David Clark
MassachusettsInstituteofTechnology
Thetermspaghetticodeisuniversallyunderstoodasaninsult.Allgoodcomputer
scientistsworshipthegodofmodularity,sincemodularitybringsmanybenefits,
including the all-powerful benefit of not having to understand all parts of a
problematthesametimeinordertosolveit.Modularitythusplaysaroleinpresenting
ideasinabook,aswellasinwritingcode.Ifabook’smaterialisorganizedeffectively—
modularly—thereadercanstartatthebeginningandactuallymakeittotheend.
Thefieldofnetworkprotocolsisperhapsuniqueinthatthe“proper”modularity
hasbeenhandeddowntousintheformofaninternationalstandard:theseven-layer
reference model of network protocols from the ISO. This model, which reflects a
layered approach to modularity, is almost universally used as a starting point for
discussionsofprotocolorganization,whetherthedesigninquestionconformstothe
modelordeviatesfromit.
It seems obvious to organize a networking book around this layered model.
However, there is a peril to doing so, because the OSI model is not really successful
atorganizingthecoreconceptsofnetworking.Suchbasicrequirementsasreliability,
flow control, or security can be addressed at most, if not all, of the OSI layers. This
facthasledtogreatconfusionintryingtounderstandthereferencemodel.Attimesit
evenrequiresasuspensionofdisbelief.Indeed,abookorganizedstrictlyaccordingto
alayeredmodelhassomeoftheattributesofspaghetticode.
Whichbringsustothisbook.PetersonandDaviefollowthetraditionallayered
model,buttheydonotpretendthatthismodelactuallyhelpsintheunderstandingof
thebigissuesinnetworking.Instead,theauthorsorganizediscussionoffundamental
conceptsinawaythatisindependentoflayering.Thus,afterreadingthebook,readers
will understand flow control, congestion control, reliability enhancement, data rep-
resentation, and synchronization, and will separately understand the implications of
addressingtheseissuesinoneoranotherofthetraditionallayers.
Thisisatimelybook.Itlooksattheimportantprotocolsinusetoday—especially
the Internet protocols. Peterson and Davie have a long involvement in and much
experiencewiththeInternet.Thustheirbookreflectsnotjustthetheoreticalissuesin
x ForewordtotheFirstEdition
protocoldesign,buttherealfactorsthatmatterinpractice.Thebooklooksatsomeof
theprotocolsthatarejustemergingnow,sothereadercanbeassuredofanup-to-date
perspective.Butmostimportantly,thediscussionofbasicissuesispresentedinaway
that derives from the fundamental nature of the problem, not the constraints of the
layered reference model or the details of today’s protocols. In this regard, what this
book presents is both timely and timeless. Thecombination of real-world relevance,
currentexamples,andcarefulexplanationoffundamentalsmakesthisbookunique.
C O N T E N T S
Foreword vii
ForewordtotheFirstEdition ix
Preface xix
1 Foundation
Problem:BuildingaNetwork 2
1.1 Applications 4
1.2 Requirements 6
1.2.1 Connectivity 7
1.2.2 Cost-EffectiveResourceSharing 10
1.2.3 SupportforCommonServices 15
1.3 NetworkArchitecture 19
1.3.1 LayeringandProtocols 20
1.3.2 OSIArchitecture 26
1.3.3 InternetArchitecture 27
1.4 ImplementingNetworkSoftware 30
1.4.1 ApplicationProgrammingInterface(Sockets) 31
1.4.2 ExampleApplication 33
1.4.3 ProtocolImplementationIssues 36
1.5 Performance 40
1.5.1 BandwidthandLatency 40
1.5.2 Delay×BandwidthProduct 44
1.5.3 High-SpeedNetworks 46
1.5.4 ApplicationPerformanceNeeds 48
1.6 Summary 50
OpenIssue:UbiquitousNetworking 51
FurtherReading 52
Exercises 55
xii Contents
2 DirectLinkNetworks
Problem:PhysicallyConnectingHosts 64
2.1 HardwareBuildingBlocks 66
2.1.1 Nodes 66
2.1.2 Links 67
2.2 Encoding(NRZ,NRZI,Manchester,4B/5B) 75
2.3 Framing 79
2.3.1 Byte-OrientedProtocols(BISYNC,PPP,DDCMP) 80
2.3.2 Bit-OrientedProtocols(HDLC) 83
2.3.3 Clock-BasedFraming(SONET) 84
2.4 ErrorDetection 88
2.4.1 Two-DimensionalParity 89
2.4.2 InternetChecksumAlgorithm 90
2.4.3 CyclicRedundancyCheck 92
2.5 ReliableTransmission 97
2.5.1 Stop-and-Wait 98
2.5.2 SlidingWindow 101
2.5.3 ConcurrentLogicalChannels 110
2.6 Ethernet(802.3) 111
2.6.1 PhysicalProperties 112
2.6.2 AccessProtocol 114
2.6.3 ExperiencewithEthernet 119
2.7 TokenRings(802.5,FDDI) 120
2.7.1 PhysicalProperties 121
2.7.2 TokenRingMediaAccessControl 122
2.7.3 TokenRingMaintenance 125
2.7.4 FrameFormat 126
2.7.5 FDDI 127
2.8 Wireless(802.11) 131
2.8.1 PhysicalProperties 132
2.8.2 CollisionAvoidance 133
2.8.3 DistributionSystem 134
2.8.4 FrameFormat 136
2.9 NetworkAdaptors 137
2.9.1 Components 138
2.9.2 ViewfromtheHost 139
2.9.3 MemoryBottleneck 144
2.10 Summary 146
Contents xiii
OpenIssue:DoesItBelonginHardware? 147
FurtherReading 148
Exercises 150
3 PacketSwitching
Problem:NotAllNetworksAreDirectlyConnected 164
3.1 SwitchingandForwarding 166
3.1.1 Datagrams 168
3.1.2 VirtualCircuitSwitching 170
3.1.3 SourceRouting 177
3.2 BridgesandLANSwitches 180
3.2.1 LearningBridges 181
3.2.2 SpanningTreeAlgorithm 185
3.2.3 BroadcastandMulticast 189
3.2.4 LimitationsofBridges 190
3.3 CellSwitching(ATM) 192
3.3.1 Cells 193
3.3.2 SegmentationandReassembly 198
3.3.3 VirtualPaths 203
3.3.4 PhysicalLayersforATM 204
3.3.5 ATMintheLAN 205
3.4 ImplementationandPerformance 210
3.4.1 Ports 212
3.4.2 Fabrics 216
3.5 Summary 220
OpenIssue:TheFutureofATM 221
FurtherReading 221
Exercises 223
4 Internetworking
Problem:ThereIsMoreThanOneNetwork 234
4.1 SimpleInternetworking(IP) 236
4.1.1 WhatIsanInternetwork? 236
4.1.2 ServiceModel 238
4.1.3 GlobalAddresses 250
4.1.4 DatagramForwardinginIP 252
4.1.5 AddressTranslation(ARP) 258
4.1.6 HostConfiguration (DHCP) 263
xiv Contents
4.1.7 ErrorReporting(ICMP) 266
4.1.8 VirtualNetworksandTunnels 267
4.2 Routing 271
4.2.1 NetworkasaGraph 272
4.2.2 DistanceVector(RIP) 274
4.2.3 LinkState(OSPF) 282
4.2.4 Metrics 291
4.2.5 RoutingforMobileHosts 295
4.3 GlobalInternet 299
4.3.1 Subnetting 301
4.3.2 ClasslessRouting(CIDR) 306
4.3.3 InterdomainRouting(BGP) 308
4.3.4 RoutingAreas 316
4.3.5 IPVersion6(IPv6) 318
4.4 Multicast 331
4.4.1 Link-StateMulticast 332
4.4.2 Distance-VectorMulticast 332
4.4.3 ProtocolIndependentMulticast(PIM) 336
4.5 MultiprotocolLabelSwitching(MPLS) 340
4.5.1 Destination-BasedForwarding 340
4.5.2 ExplicitRouting 346
4.5.3 VirtualPrivateNetworksandTunnels 348
4.6 Summary 352
OpenIssue:DeploymentofIPV6 353
FurtherReading 354
Exercises 355
5 End-to-EndProtocols
Problem:GettingProcessesstoCommunicate 374
5.1 SimpleDemultiplexer(UDP) 376
5.2 ReliableByteStream(TCP) 378
5.2.1 End-to-EndIssues 379
5.2.2 SegmentFormat 382
5.2.3 ConnectionEstablishmentandTermination 384
5.2.4 SlidingWindowRevisited 389
5.2.5 TriggeringTransmission 395
5.2.6 AdaptiveRetransmission 397
5.2.7 RecordBoundaries 401