Bi 7ATM NetworksWhy ATM? BISDN Reference ModelATM LayerATM Adaptation Layer

Chapter 9ATM NetworksWhy ATM?

The Integrated Services VisionMang in thoai ban u toan tng tTruyn dn & Chuyn machChuyn dn sang phn loi toan s1960s: truyn dn mang loi chuyn sang s1970s: chuyn mach chuyn thanh sVong thu bao t khach hang n mang vn con la tng tTm nhin cho Dich vu tich hp:Mang cn phai s t u cui n u cuiMang cn h tr tt ca cac dich vu: telephone, data, videoBa giai phap cho Integrated Services NetworkISDN in 1980sATM/BISDN in 1990sInternet in 2000s

Basic rate interface (BRI): 2B+DBRIPRIBRIPRICircuit-switched networkPrivate channel-switched networkSignalingnetworkPacket-switched networksIntegrated Services Digital Network (ISDN)Primary rate interface (PRI): 23B+DISDN: Integrated access to end-to-end digital communication services through a standard set of user-to-network interfacesNetwork consisted of separate networks for voice, data, signalingB=64 kbpsD=16 kbps

Broadband ISDNBISDN: Mt single universal network mm deo co th cung cp tt ca cac dich vu ngi dungISDN khng ap ng c: nhu cu cn 10s to 100s Mbps cho kt ni LAN va digital TVSynchronous Transfer Mode (kt ni nx64 kbps) ban u c ky vong BISDN, nhngAsynchronous Transfer Mode (ATM) c chonMultiplexing & switching frameworkconnection-oriented virtual circuitsfixed-length packets, cells, with short headers

u im cua ATMC s ha tng mang va quan ly c n gian hoa do s dung mt ch duy nht cho mangKy vong s dung LAN, MAN, va WANKha nng quan ly bng thng rng raiSONET-like grooming capabilities, but at arbitrary bandwidth granularitiesATM khng bi gii han bi tc va c ly50-600 Mbps for ATMCac thuc tinh QoS cua ATM cho phep vn chuyn voice, data, va video, vi vy lam cho ATM phu hp cho mang a dich vu

Pham vi ky vong cua ATMTt ca thng tin truyn bi mang x ly cac cell 53bytesCo th m rng v tc Giai phap chuyn mach lam vic LAN, MAN, hoc WAN

ATM Networking

AAL chuyn Thng tin thanh Cells

Thit lp kt ni thit lp knh ao bng cach t pointers trong cac bang trn ng qua mangTt ca cac cells cho mt kt ni i theo mt ngHeader xac inh kt niCells xp hang ch c truyn tai cac ATM switches & multiplexersCo th truyn dich vu CBR va VBR thng qua thoa thun trong qua trinh thit lp kt niPhm cht tr va mt mat co th thoa thun trc khi thit lp kt niCell-Switching Virtual Circuit

Switch thc hin oc bang va inh tuynATM switches co th thc hin nh s dung b nh chia se,Bang kt ni chia se, hoc c cu a tng t inh tuyn

ATM Switching

Lu lng packet ghep cac ng u vao Tach ra tai cac input portChuyn tip ti output port

Multiplexing in ATM Switches

Call Admission Control da trn Traffic Descriptors & QoS ReqtsCell streams c giam sat tai User Network InterfaceCell Enqueueing Policy, Cell Transmission Scheduling, Flow ControlGeneralized Processor Sharing, Weighted Fair Queueing, etc.Multiplexing GainCell Multiplexing implies Delay, Jitter, LossVCswithdifferent TDs&differentQoS reqts

ATM Support for Multiple QoS Levels

Chapter 9ATM NetworksBISDN Reference Model

M hinh tham chiu BISDNUser Plane: truyn tai user information; flow control; error recoveryControl Plane: thit lp, quan ly, va ngt kt niLayer Management Plane: quan ly cac thc th lp & OAMPlane Management: quan ly tt ca cac planes

Y nghia cua PlaneBa loai mang logic tham gia vao vic phn phi cac dich vu truyn thngUser Network: truyn tai thng tin ngi dungControl (Signaling) Network: mang ban tin bao hiu thit lp, duy tri va ngt kt niManagement Network: mang thng tin quan ly: thng tin giam sat, bao canh va s liu thng k s dungMt tp giao thc ring, goi la plane, c inh nghia cho mt trong ba mang nay

ATM Layered Architecture

ATM Layered ArchitectureATM Adaptation LayerGiao din chun ti cac lp cao hnThc hin cac chc nng phi hpLam vic E2E gia cac h thng u cuiPhn oan thanh cells va tai rap ATM LayerTruyn tai CellsTao/Tach Cell-Header Dich (translation) VPI/VCICell multiplexing/demultiplexingiu khin lung va tc nghenPhysical LayerChuyn i Cell stream / bit streamTruyn dn s

Cac giao din ATMXXXXXXXXXPrivate UNIPublic UNINNIPrivate NNIPrivate ATM networkPublic UNIB-ICIPublic UNIPublic ATM network APublic ATM network BUNI: User-Network InterfaceNNI: Network-Network InterfaceB-ICI: Broadband Inter-carrier i/f

ATM Physical LayerTC Sublayer: Cell DelineationKim tra li HeaderCell Rate Decoupling (Insertion of Idle Cells)Ring cho PMDPMD Sublayer: Line codeConnectorsTai s dung cac chun cua lp vt ly hin tai

Private UNI Physical Layers UTP = Unshielded twisted pairSTP = Shielded twisted pair MMF = Multimode fiberSMF = Single-mode pairSTS = Synchronous Transport Signal

Frame formatBit rateMediaCell stream25.6 MbpsUTP-3STS-151.84 MbpsUTP-3FDDI100 MbpsMMFSTS-3c, STM-1155.52 MbpsUTP-3, UTP-5, STP, SMF, MMF coaxial pairCell stream155.52 MbpsMMF, STPSTS-12, STM-4622.08 MbpsSMF, MMF

Public UNI Physical Layers

Frame formatBit rateMediaDS-11.655 MbpsTwisted pairDS-344.736 MbpsCoaxialSTS-3c, STM-1155.52 MbpsSMFE-12.048 MbpsTwisted pairCoaxialE334.368 MbpsCoaxialJ26.312 MbpsCoaxial

Chapter 9ATM NetworksATM Layer

ATM LayerLin quan n truyn theo th t cac cells qua kt ni mangKt ni ATMim-Ni-im: mt chiu hoc hai chiuPoint-to-Multipoint: mt chiuPermanent Virtual Connections (PVC): cac kt ni dai han cung cp bng thng gia cac im u cui trong mt mang ATMSwitched Virtual Connections (SVC): kt ni ngn han thit lp nhm ap ng cho cac yu cu cua khach hang

Virtual Channel Connections: virtual circuitVirtual Path Connections: tp hp cua mt s kt ni ao (VPC) ATM Header cha thng tin v kt ni ao: 8-bit Virtual Path Identifier 16-bit Virtual Channel IdentifierATM Virtual Connections

Tai sao cell co 53 Bytes?Anh hng cua tr vao cac packet thoai co tac ng ti vic la chon kich thc cellTr tao goi ln ln theo kich c cell@64kbps: packetization delay = cell size * 125 secNu tr qua lu, cn s dung thit bi trit ting vong Europe co cac ng truyn ngn va khng cn s dung b trit ting vong, vi vy xut s dung 32 byte payloadU.S. s dung cac ng truyn dai va cn s dung cac b trit, vi vy, xut s dung 64 byte payloadThoa hip: 48 byte payload

The ATM CellGFC-undefinedUNI cells has GFC fieldNNI cells allocate these 4 bits to VPI; 4096 VPsVirtual Path Identifier8-bits: 256 VC bundlesVirtual Channel Identifier16 bits: 65,536 VCs/VPPayload Type IndicatorBit 3: data vs. OAM cellBit 2: Congestion indication in data cellsBit 1: Carried transparently end-to-end; Used in AAL5Cell Loss Priorityif 1, cell can be discarded by network

Header Error CheckThe HEC only covers the 5 bytes of the header to protect against cell misdeliverySince VPI/VCI changes at every switch, HEC must be recomputedHEC used for cell delineationTwo modes: Header Error Detection / CorrectionGenerating Polynomial: g(x)=x8+ x2+ x+ 1The pattern 01010101 is XORed to r(x); keeps idle cells from having HEC=0 and preventing cell delineationThe pattern 01010101 is XORed to r(x) in received header prior to error checking

ATM Permanent Virtual ConnectionsQuan tri mang thit lp bng nhn cng cac bang VPI/VCI tai cac switches va terminalsThi gian thit lp kt ni lu, cac kt ni keo daiATMSwitchOperator atNetwork Control Center

ATM Switched Virtual ConnectionsTerminals va switches s dung VPI/VCI xac inh trc thit lp kt ni ng, theo yu cuGiao thc bao hiu c s dung trao i vi h thng x ly cuc goiATMSwitch

Traffic ContractTrong qua trinh thit lp kt ni, ngi dung va mang thoa thun hai tp tham s cho mi kt niTraffic descriptor: ngi dung xac inh lu lng mong mun mang chuyn giupQoS requirements: ngi dung xac inh loai phm cht mang yu cu bi cac cellTraffic ContractNgi dung cn tun theo traffic descriptorMang cn chuyn cell theo cam kt QoS

Cac tham s QoSSau tham s QoSBa tham s khng c thoa thun trong qua trinh thit lp kt ni:Cell error ratio: ti l cell c chuyn bi liCell mis-insertion ratio: s cells trung binh/second bi chuyn nhmSeverely errored cell block ratio: M hay nhiu hn trong s N cells bi mt, li, hay chuyn nhm

Negotiable QoS ParametersCell Loss Ratio (CLR): ti l cells bi mtXac inh bi u tin bufferCell Transfer Delay (CTD): thoa thun maximum delay Dmax: 1-a of cells co tr it hn DmaxXac inh bi cell schedulingCell Delay Variation (CDV): Peak-to-Peak variation: Dmax-D0

Traffic DescriptorsPeak Cell Rate: tc cells/second mt ngun khng c phep vtSustainable Cell Rate: tc cell trung binh do ngun tao ra trong mt khoang thi gian daiMaximum Burst Size: s cell lin tip cc ai mt ngun co th phat tai tc peak cell rate (PCR)Minimum Cell Rate: tc cell trung binh cells/second, ngun lun c phep truynCell Delay Variation Tolerance: bin ng cell delay cho phep (tolerated) cho mt kt ni cho trc.

CBRVBRreal-timeVBRnon-real-timeABRUBRCell LossRateCell TransferDelayCell DelayVariationTrafficDescriptorsFlow ControlspecifiedspecifiedspecifiedunspecifiedunspecifiedunspecifiedPCR/CDVTPCR/CDVTSCR/BTPCR/CDVT& othersPCR/CDVTnoyesnoCBR = Constant Bit RateVBR = Variable Bit RateABR = Available Bit RateUBR = Unspecified Bit Rate PCR = Peak Cell RateCDVT = Cell Delay Variation Tolerance SCR = Sustainable Cell Rate BT = Burst ToleranceCell transfer services provided by ATM NetworkATM Service Categories

Multiplexing & QoS GuaranteesATM provides per-connection QoS guaranteesMany cell flows are multiplexed onto a common stream, so how are guarantees delivered?CBR: scheduler must ensure transmission opportunities are regularly available for each connectionReal-time VBR: expect some multiplexing gain from combining VBR flows; however need to meet delay and loss requirementsNon-real-time VBR: can attempt higher multiplexing gains, subject only to loss requirementUBR: no guarantees, but excellent performance at light trafficABR: some degree of guarantee: low CLR if source responds to network feedback; MCR can be negotiated

Traffic Contract & Call Admission ControlTraffic contract: bao gm loai dich vu ATM, traffic descriptors, yu cu QoSConnection admission control (CAC) xac inh xem mt yu cu kt ni co th c chp nhn hay khngMi switch trn ng cn xac inh xem no co th chp nhn thm lung mi trong khi vn am bao cam kt vi cac lung hin tai; nu co th, phn b tai nguyn cho lung miCAC khng c tiu chun hoa, tuy thuc vao nha cung cp dich vuCho phep mc overbooking thu c multiplexing gain khac nhauTinh cc khac nhau cho cac dich vu cung cp

Policing, Traffic Shaping, and Congestion Controlam bao v QoS chi co y nghia khi ngi dung tun theo connection contractUsage parameter control (UPC) la qua trinh cng ch thoa thun lu lng tai UNI Generic Cell Rate Algorithm co th s dung cho UPC; lin quan n thut toan leaky-bucket Non-conforming cells co th bi anh du (CLP=1) hoc loai bo Traffic shaping: ngun co th s dung TS am bao lu lng cua no tun theo connection contractCo th s dung Token bucketCongestion controlCac cell co CLP=1 bi loai bo trc khi xay ra tc nghenCac kt ni ABR phai ap ng vi thng tin phan hi tc nghen nhn c t mang

Chapter 9ATM NetworksATM Adaptation Layer

ATM Adaptation LayerAAL: giao thc E2E dung phi hp dich vu truyn tai cell do mang ATM cung cp theo yu cu cua application classes xac inhBao gm chuyn i cells va ngc lai, va cac chc nng phi hp b sung nh khi phuc inh thi, truyn tai tin cyITU inh nghia cac loai dich vu sauClass A = circuit emulationClass B = variable bit-rate videoClass C & D = packet transmission

Cu trc giao thc AALAAL co hai lp con:Segmentation & ReassemblyPhn oan PDUs thanh cell payloads; Tai rap PDUs t cell payloads nhn cConvergenceCommon Part: packet framing va error detection yu cu bi tt ca AAL usersSpecific Part: cac chc nng phu thuc vao yu cu ring cua AAL user classesATMHigher Layers

AAL1Cung cp truyn dn CBR

AAL2Truyn dn co hiu qua bng thng cac dich vu tc thp, lu lng packet ngn vi yu cu tr thpB sung thm lp multiplexing th 3 cho cu truc VP/VC cua ATM, vi vy cac low-bit-rate users co th chia se mt kt ni ATM.

AAL2

AAL3/4Why 3 / 4 ?AAL3: Truyn dn d liu connection-oriented AAL4: Truyn dn d liu connectionlessTt ca packet connectionless s dung cung mt VPI/VCI tai UNIMultiplexing ID (MID) dung phn bit connectionless packetsAAL3 va AAL4 kt hp thanh AAL co th dung cho truyn dn connection-oriented hay connectionlessAAL3/4 cho phep nhiu ngi dung c ghep knh va ghep xen (interleaved) trong cung ATM VCMessage mode: ban tin cua mt ngi s dung phn oan thanh ATM payloadsStream mode: mt hoc nhiu ban tin phn oan thanh ATM payloads va phn phi khng cn chi ra phn inhAssured mode: phn phi ban tin khng liNon-Assured mode: ban tin co th c phn phi co li hoc khng co li

AAL 3/4

Higher layerCommon part convergence sublayerSAR sublayerATM layerPTI = 0Service specific convergence sublayer48 (1)InformationTPADInformation48 (0)48 (0)PTI = 0PTI = 1AAL5n gian hn than AAL3/448 bytes payloadTruyn tng packet cho VCI PTI in ATM header indicates last cell for a given packet

Examples: Voice and VideoVoiceAAL1 for individual PCM voice callsAAL1 with structured transfer for nx64 kbpsAAL2 for low-bit-rate cellular voiceAAL5 for inexpensive voiceCBR MPEG2 VideoTiming recovery at AAL or at MPEG systems layer?Error detection & correction at which layer?Timing recovery at MPEG2 systems level and AAL5 over CBR ATM was selected

Example: ATM & ADSLIP over PPPoE frames segmented by AAL5 into ATM cells at ADSL modemATM cells flow through DSLAM and ATM network to Internet Service Provider ISPDSL Access MuxUser PremiseCentral OfficeTelephoneSwitchTelephoneNetworkATMNetworkIPPPPoEAAL5ATMADSLsplittersplitterSubscriber loop

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