Lecture5-Packet Switching Networks.ppt

Bai giangMang Vin thngTrn Xun NamKhoa V tuyn in tHoc vin Ky thut Qun s *

Trn Xun Nam, Hoc vin KTQS

Bi 5Packet-Switching NetworksNetwork Services and Internal Network OperationPacket Network TopologyDatagrams and Virtual CircuitsRouting in Packet NetworksShortest Path Routing*


Chng 3 Packet-Switching NetworksNetwork Services and Internal Network Operation

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Network LayerNetwork Layer: Lp phc tap nhtYu cu cac iu phi cua cac phn t mang phn tan theo ia ly (switches & routers)Cn phai lam vic vi pham vi rt rngHang ti ngi dung (ngi & thit bi lin lac)Cac thach thc ln nhtAddressing: thng tin cn chuyn ti u?Routing: s dung ng nao a thng tin ti ich?*/96


Packet SwitchingTruyn thng tin dang mt goi n hay nhiu goi nhoTruyn goi n yu cu v chinh xac va tr truynTruyn nhiu goi nho, ngoai yu cu chinh xac, tr truyn con yu cu thm v th t cac goi va am bao quan h thi gian gia cac goi nho*/96


Network ServiceNetwork layer co th cung cp nhiu dich vu cho transport layerConnection-oriented service hay connectionless serviceBest-effort hay delay/loss guarantees*

Connection Oriented ServiceTransport layer khng th yu cu truyn cho n khi a thit lp xong kt niNetwork layer c thng bao trc v lung d liu gi vao mangTrong qua trinh thit lp kt ni co thoa thun v s dung va QoS, va trao i tai nguyn mangYu cu co ngt kt niPhc tap hn connectionless service

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Connectionless Servicen gianChi cn hai thao thac gia network layer v transport layerPhia phat: yu cu gi packetPhia thu: chi thi a co goi ti Giao trach nhim v kim soat li, th t packets, iu khin lung cho E2E transport layer

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Network Internal OperationConnectionless operationPackets truyn qua mang dang datagramMi packet c inh tuyn c lpCac packets co th c truyn qua cac ng khac nhau va co th n khng theo th tConnection-oriented operationPacket i qua cac ng ao (virtual circuits) a c thit lp t ngun ti ichVirtual circuit c thit lp mt ln va cac packet c chuyn tip qua ng thit lp Co th am bao bng thng, tr va tn hao*/96


Network Service vs. OperationNetwork ServiceConnectionlessDatagram TransferConnection-OrientedTin cy va co th truyn ng dung co tc bit khng i (constant bit rate)Internal NetworkConnectionlessIPConnection-OrientedTelephone connectionATMCac kt hp co th coConnection-oriented service over Connectionless operationConnectionless service over Connection-Oriented operationTuy trng hp & yu cu xac inh*

Cac chc nng cua Network Layer

Routing: la c cu xac inh mt tp hp cac ng tt nht inh tuyn cac packet; yu cu hp tac cua cac phn t trong mangForwarding: truyn cac packets t u vao NE ti u ra NEPriority & Scheduling: xac inh th th truyn packet cua mi NETuy chon: congestion control, segmentation & reassembly, security

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Chapter 7Packet-Switching NetworksPacket Network Topology

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c im mang chuyn mach goiPacket networks rt khac bit so vi telephone networksCac dong packet mang tnh cht cm (bursty) S dung Statistical Multiplexing tp trung cac dongNhu cu ngi dung co th thay i rt nhanhCac ng dung peer-to-peer kich thich s phat trin manh v dung lng lu lngCu truc Internet rt phn tan (decentralized)Cac ng packets i qua co th i qua nhiu mang c kim soat bi nhiu t chc khac nhauKhng co mt thc th nao chiu trach nhim cho dich vu end-to-end*/96


Access MultiplexingLu lng packet t cac ngi dung c ghep knh tai im truy nhp vao mang thanh cac dong kt hpLu lng DSL ghep knh tai DSL Access Mux (DSLAM)Lu lng Cable modem ghep knh tai Cable Modem Termination System*/96


Home LANsHome RouterLAN Access using Ethernet or WiFi (IEEE 802.11)Private IP addresses in Home (192.168.0.x) using Network Address Translation (NAT)Single global IP address from ISP issued using Dynamic Host Configuration Protocol (DHCP)HomeRouterTopacketnetworkWiFiEthernet*/96


LAN ConcentrationLAN Hubs and switches in the access network also aggregate packet streams that flows into switches and routersSwitch / Router*/96


RRRRSSSs s s s ssssss R sRBackboneTo Internet or wide area networkOrganization ServersDepartmental ServerGatewayCampus NetworkOnly outgoing packets leave LAN through routerHigh-speed campus backbone net connects dept routersServers have redundant connectivity to backbone*

Interdomain levelIntradomain levelAutonomoussystem ordomainBorder routersBorder routersInternet service providersssLANConnecting to Internet Service ProviderCampusNetworknetwork administeredby single organization*

Internet BackboneNetwork Access Points: set up during original commercialization of Internet to facilitate exchange of trafficPrivate Peering Points: two-party inter-ISP agreements to exchange traffic*/96


Vai tro cua RoutingChuyn packet nh th nao t ni nay n ni khac?Ban cht khng tp trung cua Internet lam cho routing tr thanh mt thach thc chinhCac giao thc Interior gateway protocols (IGPs) c s dung xac inh cac tuyn trong mt domainCac giao thc Exterior gateway protocols (EGPs) c s dung xac inh cac routes qua cac domainsCac routes phai nht quan & tao cac dong n inhKha nng m rng yu cu ap ng s phat trinCu truc phn cp cua ia chi IP co y nghia thit yu gi kich thc bang inh tuyn co th quan ly c*/96


Chapter 7Packet-Switching NetworksDatagrams and Virtual Circuits

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Chc nng chuyn machKt ni ng cac u vao ti u raCho phep chia se ng cac ngun tai nguyn truyn dnHai giai phap c ban:ConnectionlessConnection-Oriented: Call setup control, Connection control*/96


Packet Switching NetworkPacket switching networkChuyn packets gia cac ngi s dungCac ng truyn dn + packet switches (routers)Bt ngun t message switchingHai ch cng tac:ConnectionlessVirtual Circuit

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Message switching phat minh cho in baoToan b cac ban tin c ghep vao cac ng chia se, lu gi & chuyn tipu ban tin s dung anh ia chi source & destinationinh tuyn tai chuyn mach ban tinConnectionless

Message Switching*

Tr trong Message SwitchingCo th co tr xp hang tai mi tuyn

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Messages dai hay PacketsApproach 1: send 1 Mbit messageProbability message arrives correctly

On average it takes about 3 transmissions/hopTotal # bits transmitted 6 Mbits1 Mbit messageHow many bits need to be transmitted to deliver message?Approach 2: send 10 100-kbit packetsProbability packet arrives correctly

On average it takes about 1.1 transmissions/hopTotal # bits transmitted 2.2 Mbits*

Packet Switching - DatagramBan tin c chia nho thanh cac n vi d liu nho hn (packets)ia chi source & destination packet headerConnectionless, cac packet c inh tuyn c lp (datagram)Packet co th n khng theo trinh tPipelining cac packets qua mang co th giam tr, tng thng lngTr thp hn message switching, thich hp cho lu lng tng tac*

Minimum Delay = 3 + 5(T/3) (single path assumed)Co th co tr xp hang tai mi tuynPacket pipelining cho phep message n sm hnTr trong Packet SwitchingGia thit 3 packets trong 1 message i qua cung 1 ng*

Tr cho ban tin k-Packet qua L chng*

Bang inh tuyn trong Datagram NetworksRoute c xac inh bi bang traQuyt inh inh tuyn lin quan n vic tim ra chng tip theo trn tuyn ti ich xac inhBang inh tuyn co mt gia tri cho mi ich xac inh cng ra ti chng tip theoKich thc cua bang tr nn qua ln khi s tram ich rt ln

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Vi du: Internet RoutingGiao thc IP s dung chuyn mach goi datagram qua cac mangCac mang c coi nh cac ng lin kt d liuCac hosts co ia chi IP hai phn:Network address + Host addressCac routers tra bang theo network addressGiam kich thc cua routing table

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Packet Switching Virtual CircuitThit lp mt ng c inh gia ngun va ich trc khi truyn d liuTt ca cac packets trn mt kt ni i theo cung mt ngCo th s dung cho dich vu variable bit ratesTr bin i t, nhng vn con ln hn so vi circuit switchingCo th phn phi tai nguyn trn mi tuyn theo yu cu*

Connection SetupCac ban tin bao hiu lan truyn khi chon c tuynCac ban tin bao hiu xac inh kt ni va thit lp cac bang chuyn tip trong switchesTai u vao mi switch, kt ni c xac inh bi mt nhan goi la Virtual Circuit Identifier (VCI)Mi switch chi cn bit quan h gia nhan (VCI) u vao va nhan (VCI) u ra ti switch tip theoKhi bang chuyn tip thit lp, packets co th i theo doc ng a thit lp*/96


Tr thit lp kt niTr thit lp kt ni xay ra trc khi truyn packetTr co th chp nhn c khi truyn mt s lng ln cac packetsTr khng th bo qua khi truyn s lng packet it*/96


Bang Chuyn tip cua Virtual CircuitMi input port cua switch co mt bang chuyn tipTim VCI cua trong header cua packet tiXac inh output port (next hop) va chen VCI cho tuyn tip theoTc x ly cao do dai VCI ngn (s kt ni max cho 1 input port)Bang co th bao gm ca u tin hay cac thng tin khac*

Cut-Through switchingMt s mang chi thc hin kim soat li header nn packet co th chuyn tip ngay sau khi thu va x ly xong headerCho phep giam tr*/96


Message vs. Packet Minimum DelayMessage:L t + L T = L t + (L 1) T + T

PacketL t + L P + (k 1) P = L t + (L 1) P + T

Cut-Through Packet (Chuyn tip ngay sau khi nhn header)= L t + T

Cha tinh n tr x ly header

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Vi du: ATM NetworksTt ca thng tin anh xa thanh cac packet co dai c inh (53bytes) goi la cellsThit lp kt ni qua mangThit lp virtual circuits qua mangThit lp bang tai cac ATM switchesCac dich vuConstant bit rate connectionsVariable bit rate connections*/96


*****Private Network Addresses are 192.168.x.x, 172.16.x.x through 172.31.x.x, and 10.x.x.x ******7-9The text boxes are callouts or labels.************

Lecture5-Packet Switching Networks.ppt

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