Class Note for EECS 563 with Professor Frost at KU
Class Note for EECS 563 with Professor Frost at KU
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Date Created: 02/06/15
ATM and Frame Relay 14 Victor S Frost Dan F Servey Distinguished Professor Electrical Engineering and Computer Science University of Kansas 2335 Irving Hill Dr Lawrence Kansas 66045 Phone 785 8644833 FAX785 8647789 email frosteecskuedu httpwwwittckuedu Section 7 6 and Chapter 9 ATM ATM I ATM is a high speed low delay switching technology using short fixed size packets called cells I It combines the benefits of both circuit switching low and constant delayL guaranteed capacity and packet switching flexibilitv efficiencv for burstv traffic by using the cell switching technique to support the transmission of multimedia traffic such as voice Video image and data ATM ATM Key Attributes I Fixed length frames I Virtual circuit operation I 208 I Support dynamic bandwidth allocation I Same technology for ATM LANs and WANs Billing ATM ATM cell format 5 octets 48 octets Header Information ltr 53 octets ATM ATM I Bandwidth on Demand I Payload I VC1 I Payload I VC1 I Payload I VC2 I I Scalable Networking gt Add capacity by adding ATM switches A39IM Switch Switch ATM Switch A39IM Switch ATM CutThrough Switching Store and Forward Packet Switching ATM 6 ATM CutThrough Switching ATM ATM CutThrough Switching CutThrough Switching Segmenting large PDU s into ATM cells and using cell switching provides cutthrough like performance Multiplexing at the cell level can guarantee Q08 requirements ATM Why ATM Suitable of multiple types of traffic each with different QoS requirements High speed low delay networks for real tirne computing and command and control environments Consolidate gt networks and minimize the variety of network elements gt network management systems High speed network to interconnect LANs over wide area High speed high capacity LANs and or backbone networks ATM 9 HOW Does ATM Work 1 of 3 I All traffic whether voice video image or data is divided into 53octet cells and routed in sequence across the ATM network I Routing information is carried in the header of each cell I Routing decisions and switching are performed by hardware in the ATM switches 10 ATM How Does ATM Work 2 of 3 I ATM is connectionoriented an endtoend connection must be established and routing tables set up prior to cell transmission l Cells are reassembled into voice Video image or data at the destination ATM 1 1 How Does ATM Work3 of 3 Voice Video Data Voice Video Data BISDN BISDN Services Services g lexing gt Segmentation Reassembly E Multiplexing Demultip n J ATM I Mb m 1 53 m nnnnn BEBE ATM 1 2 ATM Protocol Reference Model User controlled ondernand fast Managxment Plane low Under Control of network provider Control Plane User Plane Higher Layers Higher Layers ATM Adaptation Layer ATM Layer Physical Layer Information flow very fast ATM 13 i Management Plane ontrol glane User Plane Class A Class B Class c Class D Connection Connection signaiing Constant Eiit Oriented less 8 C quotquot39 39 Services for Services for Data Data AAL 34 AAL 1 AAL 2 AAL 34 orAAL 5 AAL 5 ATM Adaptation Layer convergence Subiayer Service Dependent ieg ent io nd eass eml y s iaye ATM Layer Service Independent Cell Formatting Physical Layer lmr m39is39 quot quot rgel SENTquot Physical Medium Subiayer ATM 14 ATM Information Transport Protocol User Network User Error Recovery 8t Flow Control Higher Hi her Layer lt Endtosnd gt Lgyer AAL lt EdgeoEdge gt AAL ATM ATM ATM ATM Layer Layer Layer Layer Physical Physical Physical Physical Layer Layer Layer Layer ATM 1 5 Functions of the ATM Layers Higher layers High layerfunctions ATM Cg gf arafrme Convergence Adaptation Layer Segmentation and Reassembly Segmentation and reassembly Sublayer General flow control Cell Header generationextraction ATM Layer Cell VPlNCl translation Cell multiplexing Cell rate decoupling Transmission HEC sequence generationverification Convergence Cell delineation Physical Sublayer Transmission frame adaptation Layer Transmissionframegenerationreco Physical Medium Sublayer Bit timing Physical medium ATM 1 6 ATM Layer Cell Header Structure 8 7 6 5 4 3 2 1 I I I I I I Generic Flow Control GFC Virtual Path Identifier VPI VPI Virtual Channel Identi er VCI VCI VCI Payload Type PT CLP Header Error Control HEC At the NNI the GFC eld becomes part of the VPI field CLP Cell Loss Priority ATM 1 7 ATM Layer I Virtual Paths Virtural Circuits VC JVHIII Transmission Path VC illD ATM 1 8 VP ampVC s PC Pmmool ummecuon Sdcmi lr W 19 y VP ampVC 5 SWItches Vleillh VCI VCJ VCZVP1 VPI VC VC VC5 vc v1gt2 VP2 vc Wm VC VCl vcs VCl v vcz vc1 quot 1 VcsVF3 VPJ m1 VG VCS VF vcz VC VPZ VCI VCI V vcz vc2quot um 20 ATM Layer Payload Type Indicator Encoding eldei39ng Interpretation 000 User data cell congestion not experienced SDUtype 0 001 User data cell congestion not experienced SDUtype 1 010 User data cell congestion experienced SDUtype 0 011 User data cell congestion experienced SDUtype 1 100 Segment 0AM F5 owrelated cell 101 Endtoend 0AM F5 owrelated cell 110 Reserved for future traf c control and resource man 111 Reserved for future functions OAM Operations Adminstration and Mainteance SDU Service Data Unit SDUtype 01 gt End of AAL 5 PDU ATM Forward Explicit Congestion Notification FECN I Switches de ne a congested state I Cells encountering switches in a congested state set congestion experienced bit I Destination informs the source about congestion I Sources reacts to congestion ATM Layer ATM Switch Architecture Maybe external Control Processor Processor Input Output Controllers commllers 1 gt gt 1 I Input I Output Ports Fons N gtIl ATM 23 AAL Serv1ces i Service Class A Class B Class C Class D Timing ngr 922d Related Not Related Destination Bit Rate Constant Variable Connection 5 t D t d Mode quotquot 39 quot quot9quot e Connectionless Circuit 5 f onnec Ion Examples E39quot 39aquot quot Lz vhzgrfs e oriented Connectionless Ser fces Constant Bit Data Data Rate Video Evolving Transfer Transfer and Audio AAL AAL 34 AAL 34 TYPE AAquot 1 AAquot 2 AAL 5 AAL 5 ATM ATM Adaptation Layer AALl I Supports constant bit rate data with specific requirements for delay delay jitter and timing e g PCM voice CBR video and emulation of T carrier circuits DS l DS 3 I Receives constant bit rate stream with a well defined clock from source and delivers the same to the destination I Provides for timing recovery synchronization and indication of lost information ATM ATM Adaptation Layer AALl I Consists of 1 octet header PCI and 47 octets of payload I Sequence Number SN A 1bit Convergence Sublayer Indication and 3bit sequence count to detect deletion or incorrect insertion of cells ATM ATM Adaptation Layer AALl I Sequence Number Protection SNP 3bit CRC with even parity for detecting and correcting SN error 4 bits 4 bits 47 octets SN SNP SARPDU Payload ATM ATM Adaptation Layer AAL2 I New evolving standards will enable multiplexing within a ATM VC I ATM efficiently carries heterogeneous traffic in high speed networks ATM ATM Adaptation Layer AAL2 Applying ATM in lowbit rate Mobile networks I Problem gt Communications between base station controller BSC and mobile switching center MSC gt Low bit rate links eg 2 Mb s gt Voice applications gt delay constraint gt Wait to fill ATM cell induces undesirable packetization delay ATM ATM Adaptation Layer AAL2 Applying ATM in lowbit rate Mobile networks I Solution gt Layered cell structure gt Makes better use of bandwidth gt Improves control over packetization delay I Layered cell structure permits the multiplexing of multiple channels on one ATM VC ATM 30 ATM Adaptation Layer AAL2 Properties of AAL Channels l Channels have fixed length PDU I 8 bit channel identifier CID I 3 byte packet header PH per channel I 1 byte start field SF per Channel ATM ATM Adaptation Layer AAL2 Applying ATM in lowbit rate Mobile networks I lt 53 ATM gt I T l Cell ATM Hiiler D 5 1 3 Left over form previous cell D 1 Byte Start Field STF D Data D 3 Byte PaCket Header PH Channel continued between cells ATM 32 ATM Adaptation Layer AAL2 Features I Channel can ow across ATM Cell boundaries STF points to beginning of first channel in the ATM Cell I Each channel has a fixed maximum length negotiated at call set up I A fixed timer TimerCU is started per channel I Upon timer interrupt the cell is padded out and transmitted I The timer guarantees predictable delay ATM ATM Adaptation Layer AAL2 PH and STF Formats PH STF 8 bits 6 bits 5 bits 5 bits 6 bits 1 bit 1 bit CID Ll UUl HEC OSF SN P OSF Offset field CID Channel identifier SN Sequence number Ll Length indicator UUl User to user information P Determines cell loss Parity check Reserved for use by upper layers Detects arm is STF HEC Header error control ATM ATM Adaptation Layer AAL2 Common Part Sublayer on Transmit I Constructs the 3 byte header I Adds user data and header into ATM cell I Manages AALZ timer I Updates start field I Manages buffering data for transmission gt Waiting for more user data gt Padding and transmitting if tuner fires ATM ATM Adaptation Layer AAL2 Common Part Sublayer on Receive I Appends offset bytes from previous cell I Processes PH gt Discards if HEC error gt Discards if invalid CIR or L1 I Note tracking user data across multiple cells is a complex function ATM 3 6 ATM Adaptation Layer AALS I AALS is a siInple and efficient AAL SEAL to perform a subset of the functions of AAL 4 I AALS is designed to support only message mode non assured operation I The PTI field of the cell header identifies the beginning or end of the CPCS PDU gt PTT 0X1 EndofMessage EOM gt PTT 0X0 BeginningofMessage BUM or Continuation ofMessage COM 047 1 1 2 4 CPCSPDU Payload PAD Ic s CPI ILength ICRC32l ATM Bearer ClassesService Categories the service you buy Guaranteed Classes I CBR Constant Bit Rate 39 rt39VBR Real Tune Variable Bit Rate 39 nrt39VBR Non Real Tune Variable Bit Rate 39 AER Available Bit Rate 39 GFR Guaranteed Frame Rate Best Effort Classes I UBR Unspecified Bit Rate ATM 38 Some ATM Traffic Descriptors I Peak Cell Rate PCR I Sustainable Cell Rate SCR I Maximum Burst Size MBS I Minimum Cell Rate MCR I Cell Delay Variation Tolerance CDVT ATM ATM QoS Descriptors I PeaktoPeak cell delay variation I Maximum cell transfer delay I Cell Loss ratio I ATM 208 Contract gt Traffic gt Shaping gt Services gt 208 gt Compliance gt Policing gt Generic Cell Rate Algorithm GCRA like a leaky bucket algorithm is used for shaping and policing ATM Bearer Class Attributes ATM Layer Bearer Classes Attribute CBR I tVBR nI tVBR ABR UBR Cell LOSS Ratio Spec Specified Specified lietwl rk Unspecified necI c Delay and Jitter Spec Specified Unspecified Unspecified Unspecified Peak Rate Spec Specified Specified Specified Specified Sustainable Rate NA Specified Specified NA NA Minimum Rate NA NA NA Specified NA Feedback Unsp Unspecified Unspecified Specified Unspecified ATM Attribute ATM Layer Bearer Classes CBR I tVBR nI tVBR ABR UBR Network Network Cell LOSS Rat10 Guarant dGuaranteed Guaranteed Objectives Obiectives Network Network Network Delay and J1tter Guarant dGuaranteed Objectives Objectives Objectives Peak Rate Gum None None None None Sustainable Rate None Guaranteed Guaranteed None None Minimum Rate None None None Guaranteed None ATM Mapping Applications to Service Classes ATM Applications Reliability etc ATM Signaling I Used for dynamically establishing maintaining and clearing ATM connections at the User Network Interface I Based on ITU T CCITT Q2931 protocol I A specific VPCIVCI value VPCI 0 VCI 5 is used for the connection call control signaling out of band signaling I Signaling AAL SAAL is AALS SAAL provides reliable delivery ATM Frame Relay I Key enablers gt High Speeds gt Low Error Rates gt Predates ATM gt Provides access to ATM backbone services gt ISDN Standards Development ATM Frame Relay Provides Data Networking ServiceInterfaceProtocol I Frame Delimiting Alignment Transparency I Variable Length Frames I Frame Multiplexing via Link Level Connection Address IVirtual circuit oriented ATM Frame Relay Provides Data Networking SeniceInterfaceProtocol I Detection of Transmission Format and Operational Errors I Transparent IneOrder Transport of Frames I No Frame Acknowledgment Within the Network I Congestion Control Functions m 47 Private Line Service M48 Network Coud Service Netw ork Servxce Frame Relay Packet Format Fla gtch CR EA gtch IFC BC DE EA USER Data ch Flag W 50 Frame Relay Packet Format I DLCI Data link connection ID I C R Control Response I EA Extended Address I FC Forward Congestion Indicator I BC Backward Congestion Indicator I DE Discard Eligibility Indicator I FCS Frame Check Sequence ATM Frame Relay Layers r Higher Higher Layers Layers 37 37 LZEY E LZ pPPieE PEEL pPPieE Layer 2 Core Layer 2 Core Layer 2 Core Layer 1 Layer 1 Layer 1 l l l l User Frame Relay User Equipment Servrce Equipment ATM Frame Relay Layers I L2 Core Responsibilities gt Routing DLCI Translations gt Error Checking Discard Errored Frames gt Congestion Management Later in Talk I L2 Core Not Responsible For gt Error Correction e g Retransmission gt Flow Control e g Windows ATM Signaling in Frame Relay Networks I Initial Networks Need No Signaling gt Small Number of Logical Connections per Endpoint gt Use Permanent Virtual Circuits PVCs gt Manage PVCs with Local Management Interface LMI On DLCI1023 I Common Channel Signaling For Switched Virtual Circuits SVCs gt DLCI0 on Each Physical Link gt Level 3 Network Control Via Q931 Extended gt Common Signaling Protocol for Integrated Services ATM Frame Relay Switching my REUV i comm mum mus HANDLER 7 PhysmalChannelldenh erTE Termmal Eqmpmem W 55 Traf c and Congestion Control in Frame Relaz Negotiated Txa ic Paxametexs Pex DLCI Committed Infoma on Rate in bs C13 Committed Bum Size in bits 13c Excess BuxstSize in bits Be l Measmement Interval in sec T 13c CIlt W 56 Traffic and Congestion Control in Frame Relay Access Traffic Control I Accept and quotGuaranteequot Delivery of Up To Bc in Any T CIR I High Loss Priority DE0 I Accept Up To Bc Be More In Any T I Low Loss Priority Network May Discard If Congested DE1 I Excess Over Bc Be in T Discarded At Access Point ATM 57 Traf c and Conqeslion Control in Frame Relay msx nsmwm minim m an mesemzn n mummy x ATM 58 Traffic and Congestion Control in Frame Relay I Users can prioritize and shape at their EDGE to keep with CIR pick DLCl s set DE s I Some edge routers can rate limit in the presence of BECN indications I ACCESS Network can police set DE s I CORE will discard in the presence of congestion first DE s then others as necessary ATM Traffic and Congestion Control in Frame Relay I Network Congestion Functions I Notify Users gtFECN BECN CLLM LMI I Discard Frames With DE1 I Discard Frames With DE0 I Clear Connections etc ATM Traffic and Congestion Control in Frame Relay I Congestion Indications To User I Implicit gt Frame Discard Via Upper Protocol Levels I Explicit Congestion Notification From Network gt Forward Toward Destination FECN gt Backward Toward Source BECN CLLM LMI gt FECN functionality is used in ATM ATM Traffic and Congestion Control in Frame Relay User Reaction To Congestion Indications I Optional User Can Ignore I Rate Based Control gt Reduce Rate Upon Indication Implicit Explicit gt Gradually Increase When Cleared gt Implement With Buffered quotShapingquot or quotMeteringquot Function I Window Size Control gt Frame Losses Imply Insufficient Buffers gt Buffer Requirements Depend On VC Window Sizes gt Throughput Rate Also Affected By Window Size ATM Traffic and Congestion Control in Frame Relay User Reaction To Congestion Indications lSo Reduce Window Size During Congestion lSlowly Increase When Congestion Passes lExplicit Notification or N Correct Receptions ATM Traffic and Congestion Control in Frame Relay User Reaction To Congestion Indications Example lOver Time interval 2time to Tx W Frames I Measure gt frames with FECN set Nset gt Frames with FECN cleared N cleared ATM Traffic and Congestion Control in Frame Relay User Reaction To Congestion Indications Example I If Nset Ndeared gt 0 then reduce window to max1 7 SW I If Nset Ndeared lt 0 then increase window to Inin W1 W max ATM