network protocols handbook.pdf

96Protocols GuideTCP/IP - Network Layer ProtocolsProtocol NameRSVP-TE: Resource ReservationProtocol - Traffic ExtensionProtocol DescriptionThe RSVP-TE protocol is an addition to the RSVP protocol forestablishing label switched paths (LSPs) in MPLS networks.The extended RSVP protocol supports the instantiation of explicitlyrouted LSPs, with or without resource reservations. Italso supports smooth rerouting of LSPs, preemption, and loopdetection.The RSVP protocol defines a session as a data flow with a particulardestination and transport-layer protocol. However, whenRSVP and MPLS are combined, a flow or session can be definedwith greater flexibility and generality. The ingress node ofan LSP (Label Switched Path) uses a number of methods todetermine which packets are assigned a particular label. Oncea label is assigned to a set of packets, the label effectively definesthe flow through the LSP. We refer to such an LSP as anLSP tunnel because the traffic through it is opaque to intermediatenodes along the label switched path. New RSVP Session,Sender and Filter Spec objects, called LSP Tunnel IPv4 andLSP Tunnel IPv6 have been defined to support the LSP tunnelfeature. The semantics of these objects, from the perspectiveof a node along the label switched path, is that traffic belongingto the LSP tunnel is identified solely on the basis of packets arrivingfrom the “previous hop” (PHOP) with the particular labelvalue(s) assigned by this node to upstream senders to the session.In fact, the IPv4(v6) that appears in the object name onlydenotes that the destination address is an IPv4(v6) address.When referring to these objects generically, the qualifier LSPTunnel is used.In some applications it is useful to associate sets of LSP tunnels,such as during reroute operations or in spreading a traffictrunk over multiple paths, such sets are called TE tunnels. Toenable the identification and association of the LSP tunnels, twoidentifiers are carried. A tunnel ID is part of the Session object.The Session object uniquely defines a traffic engineered tunnel.The Sender and Filter Spec objects carry an LSP ID. TheSender (or Filter Spec) object, together with the Session object,uniquely identifies an LSP tunnel.In addition, the following additional Protocol Object Types exist:Value Object type16 Label19 Optical20 Explicit Route21 Record Route22 Hello207 Attribute SessionRelated protocolsMPLS, LDP, CR-LDP, IP, ATM, RSVP, OSPFSponsor SourceRSVP-TE is defined by IETF (http://www.ietf.org) RFC3209.Referencehttp://www.javvin.com/protocol/rfc3031.pdfMultiprotocol Label Switching Architecturehttp://www.javvin.com/protocol/rfc3209.pdfRSVP-TE: Extensions to RSVP for LSP TunnelsProtocol StructureApart from the existing message types listed in RSVP an additionalmessage type is available:Value Message type14 Hello