network protocols handbook.pdf

164Protocols GuideWAN - ATM ProtocolsProtocol NameATM PNNI: ATM Private Network-to-NetworkInterfaceProtocol DescriptionThe ATM Private Network-Node Interface (PNNI), an ATM network-to-networksignaling protocol, provides mechanisms tosupport scalable, QoS-based ATM routing and switch-to-switchswitched virtual connection (SVC) interoperability.The PNNI (Private Network-to-Network Interface) is a hierarchical,dynamic link-state routing protocol. It is designed to supportlarge-scale ATM networks. The PNNI protocol uses VPI/VCI0,18 for its messages. In addition, it uses signalling messagesto support connection establishment across multiple networks.PNNI is based on UNI 4.0 and Q.2931. Specific information elementswere added to UNI 4.0 in order to support the routingprocess of PNNI. PNNI Signalling contains the procedure to dynamicallyestablish, maintain and clear ATM connections at theprivate network to network interface or network node interfacebetween 2 ATM networks or 2 ATM network nodes. The PNNIsignalling protocol is based on the ATM forum UNI specificationand on Q.2931.PNNI Messages include:ALERTING, CALL PROCEEDING, CONNECT, SETUP, RE-LEASE, RELEASE COMPLETE, NOTIFY, STATUS, STATUSENQUIRY, RESTART, RESTART ACKNOWLEDGE, STATUS,ADD PARTY, ADD PARTY ACKNOWLEDGE, PARTY ALERT-ING, ADD PARTY REJECT, DROP PARTY, DROP PARTY AC-KNOWLEDGEProtocol StructureThe structure of the PNNI header is shown in the following illustration:• Packet length - The length of the packet.• Prot ver - Protocol Version. The version according towhich this packet was formatted.• Newest ver / Oldest ver - Newest version supported/ oldest version supported. The newest version supportedand the oldest version supported fields areincluded in order for nodes to negotiate the most recentprotocol version that can be understood by bothnodes exchanging a particular type of packet.Related protocolsATM, BISDN, SONET, AAL0-AAL5, LAN Emulation (LANE),CES, UNI, NNI, MPOA and Q.2931Sponsor SourceThe ATM protocols are based on standards developed by theITU.http://www-comm.itsi.disa.mil/atmf/sig.html#af10.1UNI 4.0 Specificationhttp://www.atmforum.com/standards/approved.htmlATM Forum approved specificationsReferencehttp://www.atmforum.com/standards/approved.html#uniATM User-Network Interface Specificationhttp://www.cisco.com/univercd/cc/td/doc/cisintwk/ito_doc/atm.htmATM OverviewPackettype2 2 1 1 1 1PacketlengthProt verNewestverOldestverReserved• Packet type: The following packet types are defined:1. Hello - Sent by each node to identify neighbornodes belonging to the same peer group.2. PTSP - PNNI Topology State Packet. Passestopology information between groups.3. PTSE - PNNI Topology State Element (Requestand Ack). Conveys topology parameterssuch as active links, their available bandwidth,etc.4. Database Summary - Used during the originaldatabase exchange between two neighboringpeers.