B-ISDN and ATM B-ISDN and ATM

ATM / B-ISDN Broadband Integrated Services Digital Network In the 1970s the telecommunications industry conceived that digital services would follow much the same pattern as voice services, and conceived a grandiose vision of end-to-end circuit switched services, known as the Broadband Integrated Services Digital Network (B-ISDN). This was conceived as a logical extension of the end-to-end circuit switched data service, ISDN. The technology for B-ISDN was going to be Asynchronous Transfer Mode (ATM), which was intended to carry both synchronous voice and asynchronous data services on the same transport. The B-ISDN vision has been overtaken by the technology of the Internet. The ATM technology survives as a low-level layer in most DSL technologies. Over fibre optic lines, the maximum Data bandwidth is 1.5 Megabits and point-to-point protocol is typically used to carry data over the B channels.

ATM / B-ISDN Asynchronous Transfer Mode (ATM) cell relay network protocol which encodes data traffic into small fixed sized (53 byte; 48 bytes of data and 5 bytes of header information) cells instead of variable sized packets as in packet-switched networks (such as the Internet Protocol or Ethernet).

Characteristics of ATM Uses small, fixed-sized cell Connection oriented Bandwidth allocation on demand Supports multiple service types Applicable to LAN and WAN

ATM Signaling UNI : User to Network Interface NNI : Network to Network Interface Different protocol in the different domain

Virtual Path / Virtual Channel Connection Identifier : VPI/VCI Physical Link : Contains multiple VPs Virtual Path : Contains multiple VCs Virtual Channel : Logical path between ATM endpoint

VP and VC Switching

ATM Cell Header PTI Payload Type Identifier(3 Bits) - 1 bit : User/Control Data. - 2 bit : Congestion flag. - 3 bit : Last Cell flag CLP Cell Loss Priority Bit HEC Header Error Check(8 Bits)

Permanent Virtual Circuit Manual updates of VPI/VCI tables in network equipment

Switched Virtual Curcuit Setup connection using UNI/NNI signaling

ATM Reference Model SAAL Signaling ATM Adaptation Layer Q.2931, Q2971 PHY SAAL Signaling ATM Adaptation Layer

ATM Service Criteria Traffic parameters Quality of Service Peak Cell Rate(PCR), Sustainable Cell Rate(SCR) Maximum Burst Size(MBS), Minimum Cell Rate(MCR) Quality of Service Maximum Cell Transfer Delay(MCTD) Cell Delay Variation Tolerance(CDVT) Cell Loss Ratio(CLR)

ATM Service Categories

Traffic Management - I CAC(Connection Admission Control) Determine whether a connection can be progressed or not - satisfy the traffic contract of the connection - not disturb traffic contracts of the other connections

Traffic Management - II UPC(Usage Parameter Control) Protect network resources from malicious as well as unintentional misbehavior - based on traffic contract of the connection - action : cell discard, cell tagging

Traffic Management - III CLP(Cell Loss Priority) Control In Congestion state - EFCI(Explicit Forward Congestion Control) - CLP(Cell Loss Priority)

Traffic Management – IV CAC / Connection Management UPC (Policing) CLP / EFCI control Frame Discard Traffic Shaping ABR Congestion Feedback

ATM Signaling Protocol Point-to-Point ATM Connection(Q.2931)

Reserved VPI/VCI Q.2971 Q.2931

Message Structure Information Element Length Protocol discriminator Distinguish Message 1 Call reference Identify call at the local UNI 4 Message type Identify the function of message 2 AAL parameter 4-21 ATM traffic descriptor 12-20 Broadband bearer capability 6-7 QoS parameter 6 …

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