计算机网络-自顶向下方法与Internet特色

ComputerNetworking

ATop-DownApproachFeaturingtheInternet

计算机网络.自顶向下方法与Internet特色

Chapter4TheNetworkLayer

Introduction

□Chaptergoals

□understandprinciplesbehindnetworklayerservices:

□routing(pathselection)

□dealingwithscale

□howarouterworks

□advancedtopics:IPv6,mobility

□instantiationandimplementationintheInternet

2

SchoolofComputerScience&Technology

roadmap

□4.1Introduction

口4.2Virtualcircuitanddatagramnetworks

□4.3What'sinsidearouter

□4.4IP:InternetProtocol

口4.5Routingalgorithms

□Linkstate、DistanceVector、Hierarchicalrouting

□4.6RoutingintheInternet

□RIP、OSPF、BGP

□4.7Broadcastandmulticastrouting

□Summary

3

SchoolofComputerScience&Technology

4.1Networklayerintroduction

□Servicesdescription

□KeyNetwork-LayerFunctions

□Routing

□Forwarding

□Connectionsetup

□Networkservicemodel

4

SchoolofComputerScience&Technology

1、KeyNetwork-LayerFunctions

4

』①Forwarding

i

n

fmovepacketsfromrouter*sinputto

r

oappropriaterouteroutput

d

u

d

i②Routing

o

n

determinetheroute(path)takenby

packetsfromsourcetodest

口routingalgorithms

5

SchoolofComputerScience&Technology

1、KeyNetwork-LayerFunctions

4

』@Connectionsetup

i

nrd

f□3importantfunctioninsomenetwork

r

oarchitectures:

d

u□ATM,framerelay,X.25

d

i

o□Beforedatagramsflow,twohostsand

ninterveningroutersestablishvirtual

connection

□Routersgetinvolved

6

SchoolofComputerScience&Technology

7

:y

eog

ol

n

ch

iec

vT

&

rce

een

lci

sS

r

erte

dpu

eom

C

oyf

lo

ao

lo

msch

rteS

eos

icps:e

vsstrc

rnr:oero

eaeh.yp

stryontao

awoiLw.

kdLtpttnd

rnknorne

oaretoeo

koetpet

wrwinswd

twetonetn

eotbpabe

we□□r□□

NetNT

、N□□

2□

4』infrodudion

2、Networkservicemodel

4

』Q:Whatstheservicemodelofthechannel

i

nconnectingthetransportinglayerinthe

f

rsendingandreceivinghosts?

o

d□Exampleservicesforindividualdatagrams:

u

d□guaranteeddelivery

i

o□Guaranteeddeliverywithlessthan40msecdelay

n□Exampleservicesforaflowofdatagrams:

□In-orderdatagramdelivery

□Guaranteedminimumbandwidthtoflow

□Restrictionsonchangesininter-packetspacing

(delayjitter)

8

SchoolofComputerScience&Technology

2、Networkservicemodel

4

』

i

nNetworkServiceuarantees.Congestion

fArchitectureModelBandwidthLossOrderTimingfeedback

r

o

dbesteffortnonenonono

uInternetno(inferred

cvialoss)

f

iATMCBRconstantyesyesyesno

oratecongestion

nATMVBRguaranteedyesyesyesno

ratecongestion

ATMABRguaranteednoyesnoyes

minimum

ATMUBRnonenoyesnono

9

SchoolofComputerScience&Technology

roadmap

口4.1Introduction

□4.2Virtualcircuitanddatagramnetworks

口4.3What'sinsidearouter

□4.4IP:InternetProtocol

口4.5Routingalgorithms

□Linkstate、DistanceVector、Hierarchicalrouting

□4.6RoutingintheInternet

□RIP、OSPF、BGP

口4.7Broadcastandmulticastrouting

口Summary

10

SchoolofComputerScience&Technology

4.2Virtualcircuitanddatagramnetworks

□Networklayerconnectionandconnection-less

service

□Virtual-CircuitNetworks

□DatagramNetworks

□DatagramorVCnetwork:why?

11

SchoolofComputerScience&Technology

Introduction

4

.

2

v□Datagramnetworkprovidesnetwork­

-

r

t

u

alayerconnectionlessservice

-

c

i

r

c□VCnetworkprovidesnetwork-layer

u

-

f

aconnectionservice

n

d

d

a□Analogoustothetransport-layerservices,

s

g

rbut:

a

m

n

e□Service:host-to-host(aka.EndtoEnd)

t

w

o

r□Nochoice:networkprovidesoneortheother

k

s

□Implementation:inthenetworkcore

12

SchoolofComputerScience&Technology

1、Virtual-CircuitNetworks

4

.

2

v

i

r

t

u

a

-

c"source-to-destpathbehavesmuchliketelephone

i

r

c

u，

icircuit\buttherearecrucialdifferencesso

f

a

ncalledvirtualcircuitratherthancircuit.

d

d•sharedordedicatedresource

a

s

g•actionsalongsource-to-destpath

r

a

m•Routerdeterminesthepackefspathaccordingto

n

etheinformationinthepacketitself

t

w

o

r

k

s

13

SchoolofComputerScience&Technology

4

y1

y

aog

ol

n

mh

)ec

wssT

snr&

loiece

kffen

aci

tfS

rr

ntnute

aoiu

ocabp

n,om

(nC

wamhf

oto

ttril

o

aehtdo

itih

edfcc

iaewS

Netpnd

orntn

tfesoan

ieid)ec

bs-dg(b

ulnCeens

caioVrcie

rctsdrsc

ieceduarC

hniaopuV

Ccnrtsoa

-acoasnhs

lecoocreo

rhethat

afoteererd

unkontrtete

tpwciufoua

rtuoaatooc

ierdpre“rlo

sahinyt,l

ltecstraka

Vaaevestine

、c□ede“lb

1□□n□

4.2v-rtua-circu-fanddasgramnetworks

VCimplementation

4

.

2

vAVCconsistsof:

-

r

t

u

a

-1.Apathfromsourcetodestination

c

i

r

c2.VCnumbers,onenumberforeachlinkalongpath

u

-

f

a3.Entriesinforwardingtablesinroutersalongpath

n

d

d

a□PacketsbelongingtoaVCcarriestheVC

s

g

rnumber.

a

m

n

e□VCnumbermustbechangedoneachlink.

t

w

o

r□VCswitching

k

s

□NewVCnumbercomesfromforwardingtable

15

SchoolofComputerScience&Technology

Virtualcircuits:signalingprotocols

4

.

2

v

-

r

t

u□usedtosetup,maintainteardownVC

a

-

c

i

r

c□usedinATM,frame-relay,X.25

u

-

f

a

n□notusedintoday'sInternet(packet

d

d

aswitchingnetworks)

s

g

r

a

m

n

e

t

w

o

r

k

s

SchoolofComputerScience&Technology

17

ty

og

sol

n

oh

hyec

aT

”&

nnmce

en

oorci

iiiS

dttr

cate

nau

epp

etm

s-nno

isC

rontef

koslo

etdo

-co

rye-h

d“ec

olanfdcS

eogur

wrktptno

toesis

eoucue

twbnm

Neacodas

nlesth

tteerdna

maaevaep

ast-lt

rpskwtwen

gtuonrreer

enoofobf

as:titwtsif

tlscetssed

alreneeke

atenokrck

Dcnncdata

ouoadp

、nroc□pa□

2□□□

4.2v-rtua-circu-fanddasgramnetworks

ForwardingtableofDatagramNet

4

.

2

v

-DestinationAddressRangeoutputLinkInterface

r

t

u

a

-

c11001000000101110001000000000000

i

r

cthrough0

u

-11001000000101110001011111111111

f

a

n

d11001000000101110001100000000000

d

athrough1

s

g11001000000101110001100011111111

r

a

m

11001000000101110001100100000000

n

ethrough2

t

w11001000000101110001111111111111

o

r

k

s323

otherwiseAtmOStz2

possibleentries

18

SchoolofComputerScience&Technology

Longestprefixmatching

4

.

2

vPrefixMatchLinkInterface

-

r

t

u1100100000010111000100

a

-

c

i1100100000010111000110001

r

c

u

-1100100000010111000112

f

a

notherwise3

d

d

a

s

gExamples

r

a

mDA：11001000000101110001011010100001

n

e

t

wWhichinterface?

o

r

k

sDA:11001000000101110001100010101010

Whichinterface?

19

SchoolofComputerScience&Technology

0

2

y

?"og

ol

en

ygh

ec

hdT

ye&

re

w"c

een

tci

:vaS

or

.te

kqcyu

reetp

rriom

C

orxf

sgelo

)olo

wrnsro

eirph

ttrc

meeS

eutit,m

nptuolco

micptr,lt

Cotrmnkcsu

csoorttiic

Vgo(cconsf

nnsweriif

ro,rmetmted

omemonuce

aicterfrgaic

vseeasarv

mgerypiddehr

anses,snpce

r1dtnyts

a1npiEtn

ghiceaed2kem

actz，dlnrr

ttxstapnliefo

aeelarnEfi

na'eaaim□yin

Drat'mcsandu

ted□'s□□□□

、nm

3I□□□

4.2v-rtua-circu-fanddasgramnetworks

?ny

og

yool

in

th

haec

sT

wr&

ece

en

:vci

S

knr

ste

otu

rcnp

oom

eC

nf

amlo

wo

tmeo

rch

euiS

nhue

reqicrk

orvo

Cfyr

yitsetw

Vnile

obdsn

rhaee

oplitmid

lereantes

mte,rysin

aguas

rmingsty

ordei

grimoennex

aftfol

tdtd"hp

aeicebep

vremlm

Dlstnueo

Modtc

ev□□"□□

、T

3A口口

4.2v-rtua-circu-fanddasgramnetworks

roadmap

□4.1Introduction

口4.2Virtualcircuitanddatagramnetworks

口4.3What*sinsidearouter

□4.4IP:InternetProtocol

口4.5Routingalgorithms

□Linkstate、DistanceVector.Hierarchicalrouting

□4.6RoutingintheInternet

口RIP、OSPF、BGP

口4.7Broadcastandmulticastrouting

口Summary

22

SchoolofComputerScience&Technology

4.3What'sinsidearouter

□RouterArchitectureOverview

□RouterFunctions:

□RouterArchitecture

□InputPortFunctions

□switchingfabric

□OutputPortsFunctions

23

SchoolofComputerScience&Technology

4

2

y

og

ol

on

th

ec

,gT

&

Pnce

Iien

ci

S

Rmr

(te

ou

lcp

oom

nC

cif

lo

oo

:to

smch

nooS

oprr

i/f

ctss

nmm

utha

frir

yoag

nelgat

ka)dk

ioogPn

tngli

cwtiGin

tBdg

usou,rin

dr*rFao

oenPwtg

rtuSru

turOfoo

InroH^

4.3whafwinsidearotifer

Introduction-Architecture

4

.

3

w

h

a

f

w

i

n

s

i

d

e

a

r

o

t

i

f

e

r

25

SchoolofComputerScience&Technology

1、InputPortFunctions

4

.

3

w

hlookup,

adatalinkforwarding

fswitch

wprocessing

i(protocol,llllllll

nqueueingfabric

sdeca%ption)

i

dPhysicallayer：

eDatalinklayer：

bit-level

aeg,Ethernet\

receptionDecentralizedswitching；

r

o口givendatagramdest.,lookupoutputportusing

tforwardingtableininputportmemory

il1

f□goal:completeinputportprocessingatlinespeed

e口queuing:ifdatagramsarrivefasterthan

rforwardingrateintoswitchfabric

26

SchoolofComputerScience&Technology

2、SwitchingFabrics

4A

.X■X

，口口limn।川川

3□o**□□1limnlimn

BY

wBY

-HZJmemory川川।

h，口口limnwniM

azz

।川川limn

f*□□1*□□1limnlimn

wbus

imemory

n

sA

iPEIlimn>

d

B

e

♦口口limn>crossbar

a

limn

r

o

t

i

f□

e

r9

27

Threetvy▲pesofswitchingJfabricsSchoolofComputerScience&Techznolo,gy

(1)SwitchingViaMemory

4

.InputMemoryOutput

3

w

h

a

f

w

i

n

s

i

d

e

a□Firstgenerationrouters:

r□traditionalcomputerswithswitchingunderdirect

o

tcontrolofCPU

i

f

e□packetcopiedtosystem'smemory

r□speedlimitedbymemorybandwidth(2buscrossings

perdatagram)SchoolofComputerScience&Technology

a

A

a

o

l

o

s

q

u

包

》

a

J

^±U

G

ouS

oJ

no~

r

-o

sBst

nT

©i

^s

V4n

MBq

.ASTos

M~n

l_

l

.IS~n

P1T

14

W

S

(

)z

4.3Whafsinsidearouter

0

3

y

og

ol

dn

dh

eeec

otetT

tsipo&

usce

ymnen

b(ci

itS

rlr

odnste

ederpu

mreieom

cC

eaeitf

lo

pfuo

mhfo

ssoh

uc

tagsrS

rne

oai:is

pvih0r)

tc0pe

uyit19rn

prweo

sinoshotb

umtscenk

Bmesidic

omnwCda

ariod,nb

afrttsar

ionanuso

Vmptebsl

ganbsea

nrtospcn

igucubao

htatpsbi

tcuuyGreg

iaob1for

wdb

S□□□

4.3whafwinsidearotifer

oy

tog

eol

mn

dhch

ate

erT

npr&

ooghce

ioagen

lsci

ttS

essur

csealte

envlou

ecderp

nooom

idchC

ntrgtf

alo

otypnho

ciliiso

lttcch

rmltpS

eliiauenib

thitwGk

Intnmmsr

idings,eso

nwsialw

Adetsfre.ht

nrcictce

iaano:rin

bnsnthbwn

Vsoesiggaso

gbuticsnf:ti

ncoeee0c

ieerdlh0e

chmnpddt20n

itontceeh1n

rccocixgo

wrkl:erenfuorc

Soavtenvaoosce

oonondtrit

)tw□icinthCin

(3eGA

N□□□□

4.3whafwinsidearotifer

SwitchingViaAnInterconnectionNetwork

4

.

3

W

h

a

s贷

i

n

s

i

d

e

a

r

o

t

i

f

e

r

SchoolofComputerScience&Technology

4、OutputPorts

4

.

3

w

ata

hqueuing^!^""

aswitch

f

wline

fabric厂(protocol,

imanagementI.vr…、termination

npdecapsulation)L

s

i

d

e口Bufferingrequired^Schedulingdiscipline

awhendatagramsarrivechoosesamongqueued

r

o

tfromfabricfasterthandatagramsfortransmission

i

fthetransmissionrateof

e

rtheoutputlink

33

SchoolofComputerScience&Technology

Outputportqueueing

4

.

3

w

h

a

f

w

i

n

s

i

dOutputPortConteniionOnePocket

eolTimetTimeLater

a□bufferingwhenarrivalrateviaswitch

r

oexceedsoutputlinespeed

t

i

f

e□queueing(delay)andlossduetooutput

r

portbufferoverflow!34

SchoolofComputerScience&Technology

InputPortQueuing

4

.

3

w

h

a--------------1

f句43-

w

iswitchI—I

n-I2F-D-fabrici一

s

i

d

e

outputportcontentiongreenpacket

aattimet-onlyoneredexperiencesHOLblocking

rpacketcanbetransferred

o

t

i

f

e

r

35

SchoolofComputerScience&Technology

6

dr3

eey

fog

dfol

eun

euch

ne

iudbT

sr&

bqte

tac

uen

m:nci

wpS

oger

snvrnte

ceioipu

efm

sukro

eoC

tcpgtf

rulo

oo

qlneo

oeih

tbc

puvuS

tpu)eod

uinLums

ptOqos

inafl

r(Hoomd

ncuetrn

gacnnfa

nthoiroey

iyLfua

uera-tel

emeaue

uwgthqd

Qlon-mng!

tseifainw

rcu-orsio

oiedgrefl

Pruataeeuer

tbqeathuv

ufa□Hdoqo

p□□□

In

4.3whafwinsidearotifer

roadmap

□4.1Introduction

口4.2Virtualcircuitanddatagramnetworks

口4.3What'sinsidearouter

□4.4IP:InternetProtocol

口4.5Routingalgorithms

□Linkstate、DistanceVector.Hierarchicalrouting

□4.6RoutingintheInternet

口RIP、OSPF、BGP

口4.7Broadcastandmulticastrouting

口Summary

37

SchoolofComputerScience&Technology

TheInternetNetworklayer

Host,routernetworklayerfunctions:

Transportlayer：TCP,UbP

RoutingprotocolsIPprotocol

,pathselection,addressingconventions

-R工P,OSPF,BGP,datagramformat

Network,packethandlingconvent