C L Morgan CS 4594 Broadband Communications ATM

C L Morgan ATM ATM = Asynchronous Transfer Mode ATM = Asynchronous Transfer Mode Asynchronous - in contrast to SONET/SDH in which large frames of data are sent on a completely regular basis, completely synchronized. Purpose: Convey voice, video, and data service over the same channel. Each service has different timing requirements. Purpose: Convey voice, video, and data service over the same channel. Each service has different timing requirements. ATM was developed to meet the new telephone network model called Broadband ISDN = Integrated Services Digital Network ATM was developed to meet the new telephone network model called Broadband ISDN = Integrated Services Digital Network

C L Morgan ATM Layers ATM has three major layers: AAL, ATM, Physical. ATM has three major layers: AAL, ATM, Physical. AAL ATM Physical AAL provides network services. Converts user data into fixed length cells (53 bytes) ATM handles switching, traffic management, etc. Physical connects to a variety of different media

C L Morgan ATM Cells ATM transports data in small packets called cells. ATM transports data in small packets called cells. Each cell is 53 bytes long with a 5 byte header and a 48 byte payload. Each cell is 53 bytes long with a 5 byte header and a 48 byte payload.

C L Morgan ATM Cell Header The ATM cell header has two different forms: The ATM cell header has two different forms: UNI = User-Network Interface - as the cell enters the network UNI = User-Network Interface - as the cell enters the network NNI = Network-Network Interface - as it moves through the network. NNI = Network-Network Interface - as it moves through the network.

C L Morgan ATM Cell Header – Fields Labeling – Cell ID Labeling – Cell ID GFC = Generic Flow Control – 4 bits for UNI, not present in NNI, misnamed, now used for multiplexing user channels GFC = Generic Flow Control – 4 bits for UNI, not present in NNI, misnamed, now used for multiplexing user channels VPI = Virtual Path Identifier – 8 bits for UNI, 12 bits for NNI VPI = Virtual Path Identifier – 8 bits for UNI, 12 bits for NNI VCI = Virtual Channel Identifier – 16 bits VCI = Virtual Channel Identifier – 16 bits Cell Management Cell Management PTI = Payload Type – 3 bits PTI = Payload Type – 3 bits CLP = Cell Loss Priority CLP = Cell Loss Priority Error Control and Framing Error Control and Framing HEC = Header Error Control – 8 bits, CRC check on header HEC = Header Error Control – 8 bits, CRC check on header

C L Morgan ATM – Virtual Circuits VPI/VCI form a label for the cell that determines how the cell will be handled in the next switch. VPI/VCI form a label for the cell that determines how the cell will be handled in the next switch. Each switch has a number of inputs and outputs, each with a identifying number. Each switch has a number of inputs and outputs, each with a identifying number. When a cell enters a switch, its VPI/VCI is input into a table look-up that returns the output identifier and a new VPI/VCI. When a cell enters a switch, its VPI/VCI is input into a table look-up that returns the output identifier and a new VPI/VCI.

C L Morgan ATM – Virtual Circuit Types PVC = Permanent Virtual Circuit – set up manually by programming each switch along the route PVC = Permanent Virtual Circuit – set up manually by programming each switch along the route SVC = Switched Virtual Circuit – set up dynamically by signaling procedures. SVC = Switched Virtual Circuit – set up dynamically by signaling procedures.

C L Morgan AAL = ATM Adaptation Layer ALL is the top layer among ATM layers ALL is the top layer among ATM layers AAL ATM Physical

C L Morgan Role of AAL Provides interface between application layers and ATM network itself Provides interface between application layers and ATM network itself Implemented in endpoint devices (at edge of network) Implemented in endpoint devices (at edge of network) Supports a number of different service classes Supports a number of different service classes Shields ATM layer from knowing anything about user data Shields ATM layer from knowing anything about user data

C L Morgan Classical AAL Classes Class Bit rate timing Connection mode Class A constant Timing critical Connection oriented Class B variable Timing critical Connection oriented Class C variable Timing tolerant Connection oriented Class D variable Timing tolerant Connection less

C L Morgan Modern Service Categories CBR = Constant Bit Rate CBR = Constant Bit Rate rt-VBR = Real Time Variable Bit Rate rt-VBR = Real Time Variable Bit Rate nrt-VBR = Non Real Time Variable Bit Rate nrt-VBR = Non Real Time Variable Bit Rate ABR = Available Bit Rate ABR = Available Bit Rate UBR = Unspecified Bit Rate UBR = Unspecified Bit Rate GFR = Guaranteed Frame Rate GFR = Guaranteed Frame Rate

C L Morgan Traffic Contract Agreement between user and network Agreement between user and network Contains Contains Traffic descriptors – specifying ATM cell flowTraffic descriptors – specifying ATM cell flow QoS parameters – specifing timing and error qualitiesQoS parameters – specifing timing and error qualities Conformance checking rulesConformance checking rules

C L Morgan Traffic Parameters PCR = Peak Cell Rate PCR = Peak Cell Rate SCR = Sustainable Cell Rate SCR = Sustainable Cell Rate MBS = Maximum Burst Size MBS = Maximum Burst Size MCR = Minimum Cell Rate MCR = Minimum Cell Rate

C L Morgan QoS Parameters Timing Timing Cell Transfer Delay (CTD)Cell Transfer Delay (CTD) Cell Delay Variation (CDV)Cell Delay Variation (CDV) Errors Errors NonegotiableNonegotiable Cell Error Ratio (CER)Cell Error Ratio (CER) Cell Misinsertion Rate (CMR)Cell Misinsertion Rate (CMR) Severely-Errored Cell Block Ratio (SECBR)Severely-Errored Cell Block Ratio (SECBR) NegotiableNegotiable Cell Loss Ratio (CLR)Cell Loss Ratio (CLR) Cell Misinsertion Rate (CMR)Cell Misinsertion Rate (CMR)

C L Morgan AAL Sublayers Service specific convergence sublayer (SSCS) Common part convergence sublayer (SSCS) Segmentation and reassembly sublayer (SAR)

C L Morgan Sublayers of AAL CS = Convergence Sublayer (CS) CS = Convergence Sublayer (CS) Performs functions such as end-to-end synchronization, traffic control and monitoring, cell loss controlPerforms functions such as end-to-end synchronization, traffic control and monitoring, cell loss control SublayersSublayers Service Specific (SSCP) – application dependentService Specific (SSCP) – application dependent Common Part (CPCS) – common to all users of a serviceCommon Part (CPCS) – common to all users of a service Segmentation and Reassembly (SAR) Segmentation and Reassembly (SAR) Performs repackaging between convergence layer packets and ATM cellsPerforms repackaging between convergence layer packets and ATM cells

C L Morgan AAL Types Designed to handle the different service types Designed to handle the different service types Specify architectural details, traffic parameters, packet formats and procedures Specify architectural details, traffic parameters, packet formats and procedures

C L Morgan AAL-0 Unofficial Unofficial Designed to send ATM cells directly from ATM-cell based application to ATM cell Designed to send ATM cells directly from ATM-cell based application to ATM cell Has empty CS and SAR Has empty CS and SAR

C L Morgan AAL-0 Operations Higher Layers ATM Cell AAL Layers ATM Layer ATM Cell

C L Morgan AAL-1 Designed for Class A= CBR Designed for Class A= CBR Transports a constant stream of bits with timing Transports a constant stream of bits with timing Applications: circuit emulation, uncompressed voice and video. Applications: circuit emulation, uncompressed voice and video. May handle: May handle: segmentation and reassembly (SAR) segmentation and reassembly (SAR) handling cell delay variation (buffering) handling cell delay variation (buffering) handling cell delay handling cell delay handling lost and mininserted cells handling lost and mininserted cells clock management clock management recovery of source data framing recovery of source data framing monitoring and correction of error in user data monitoring and correction of error in user data

C L Morgan AAL-1 PDU SAR header SAR header SN (4 bits): sequence numberSN (4 bits): sequence number CSI (1 bit): Convergence layer indicator (can be used for clock)CSI (1 bit): Convergence layer indicator (can be used for clock) Sequence number (3 bits)Sequence number (3 bits) SNP (4 bits): sequence number protectionSNP (4 bits): sequence number protection 3-bit CRC3-bit CRC 1 bit parity1 bit parity

C L Morgan AAL-1 Operations Higher Layers Bit Stream AAL Layers ATM Layer 47 (bytes) H 147 H 1 H 1 H 1 ATM CellH 548 ATM CellH 548 ATM CellH 548 ATM CellH 548 SAR CS

C L Morgan AAL-2 Designed to handle Class B, rt-VBR Designed to handle Class B, rt-VBR Transfers multiplexed streams of bits and timing Transfers multiplexed streams of bits and timing Handles errors or indicates when errors have occurred Handles errors or indicates when errors have occurred Two layers: packet and PDU (cell) Two layers: packet and PDU (cell)

C L Morgan AAL-2 Operations Higher Layers User 1 AAL 2 Layers ATM Layer ATM CellH 548 ATM CellH 548 ATM CellH 548 ATM CellH 548 User 2User 3User 1 STF 1 47 STF 147 STF 147 STF 147 H 3 H 3 H 3 H 3 packet PDU

C L Morgan AAL-2 CPS Packet CPS-PH (3 octets) common part sublayer packet header CPS-PH (3 octets) common part sublayer packet header CID (8 bits): channel id for multiplexingCID (8 bits): channel id for multiplexing LI (6 bits): length indicator for number of octets in variable payload structuresLI (6 bits): length indicator for number of octets in variable payload structures UUI (5 bits): user-to-user informationUUI (5 bits): user-to-user information HEC (5 bits): error control for packet headerHEC (5 bits): error control for packet header

C L Morgan AAL-2 CS-PDU STF (8 bits): start field STF (8 bits): start field OSF (6 bits): offsetOSF (6 bits): offset SN/P (2 bits): error correction and detection for start fieldSN/P (2 bits): error correction and detection for start field Payload data (47 bytes) Payload data (47 bytes) PAD (padding as needed for real-time) PAD (padding as needed for real-time)

C L Morgan AAL-3/4 Designed for Class C and Class D (nrt-VBR) connection and connectionless Designed for Class C and Class D (nrt-VBR) connection and connectionless Can do multicasting (network-based distribution) Can do multicasting (network-based distribution) Can do multiplexing (multiple streams through same service) Can do multiplexing (multiple streams through same service) Designed to be highly reliable Designed to be highly reliable CRC check on cellsCRC check on cells SAR supportSAR support SequencingSequencing Mux idMux id Beginning and end tagsBeginning and end tags HECHEC Multiple modes of operation (assured and non assured delivery) Multiple modes of operation (assured and non assured delivery)

C L Morgan AAL-3/4 Operations Higher Layers packet AAL Layers ATM Layer 75 (bytes) ATM CellH 548 ATM CellH 548 ATM CellH 548 ATM CellH 548 CPCS SSCS packet SAR H 475 P 5 T 4 H 4 P 5 T 4 H 4 P 5 T 4 H T H T H T H T

C L Morgan AAL-3 structures CPIBT BA size User DataPADALET Length Header (1+1+2)Trailer (1+1+2)

C L Morgan AAL-3/4 CPCS-PDU Header (4 octets) Header (4 octets) CPI (1 octets): Common Part Indicator – defines how the other parts are encodedCPI (1 octets): Common Part Indicator – defines how the other parts are encoded BT (1 octet): Beginning TagBT (1 octet): Beginning Tag BA size (1 octet): Buffer Allocation sizeBA size (1 octet): Buffer Allocation size User Data (1-65,535 octets) User Data (1-65,535 octets) PAD: padding to keep PDU length a multiple of 4 octets PAD: padding to keep PDU length a multiple of 4 octets Trailer (4 octets) Trailer (4 octets) AL (1 octet): Alignment to make CPS trailer 4 octetsAL (1 octet): Alignment to make CPS trailer 4 octets ET (1 octet): Ending TagET (1 octet): Ending Tag Length (2 octets) of entire PDULength (2 octets) of entire PDU

C L Morgan AAL-3/4 SAR-PDU Header (2 octets) Header (2 octets) ST (2 bits): Segment Type: BOM 10, COM 00, EOM 01ST (2 bits): Segment Type: BOM 10, COM 00, EOM 01 SN (4 bits): Sequence NumberSN (4 bits): Sequence Number MUX-ID (10 bits): multiplexing idMUX-ID (10 bits): multiplexing id SAR-PDU Payload (44 octets) segment of CPCS-PDU SAR-PDU Payload (44 octets) segment of CPCS-PDU Trailer (2 octets) Trailer (2 octets) LI (6 bits): length indicatorLI (6 bits): length indicator CRC (10 bits): CRC check on segmentCRC (10 bits): CRC check on segment

C L Morgan AAL-5 Designed for Class C and Class D (nrt-VBR) connection and connectionless Designed for Class C and Class D (nrt-VBR) connection and connectionless Simplified (lightweight) version of AAL-3/4 Simplified (lightweight) version of AAL-3/4 No overhead in cells No overhead in cells

C L Morgan AAL-5 Operations Higher Layers packet AAL Layers ATM Layer 75 (bytes) ATM CellH 548 ATM CellH 548 ATM CellH 548 ATM CellH 548 CPCS SSCS packet SAR 75 P 13 T P 13 T 875 P 13 T 8 48

C L Morgan AAL-5 SDUs CPCS-PDU CPCS-PDU User Data: 1-65,535 octetsUser Data: 1-65,535 octets PAD: 0-47 octetsPAD: 0-47 octets CPCS-PDU trailerCPCS-PDU trailer CPCS UU: 1 octetCPCS UU: 1 octet CPI: 1 octetCPI: 1 octet CPCS-PDU length: 2 octetsCPCS-PDU length: 2 octets CRC: 4 octetsCRC: 4 octets