RSVP-TE: Resource Reservation Protocol - Traffic Extension

RSVP-TE: Resource Reservation Protocol  - Traffic Extension
The RSVP-TE protocol is an addition to the RSVP protocol for establishing label switched paths (LSPs) in MPLSnetworks. The extended RSVP protocol (RSVP-TE) supports the instantiation of explicitly routed LSPs, with or without resource reservations. RSVP-TE also supports smooth rerouting of LSPs, preemption, and loop detection.
RSVP-TE defines a session as a data flow with a particular destination and transport-layer protocol. When RSVP and MPLS are combined, a flow or session can be defined with greater flexibility and generality. The ingress node of an LSP (Label Switched Path) uses a number of methods to determine which packets are assigned a particular label. Once a label is assigned to a set of packets, the label effectively defines the flow through the LSP. Such an LSP is an LSP tunnel because the traffic through it is opaque to intermediate nodes along the label switched path. New RSVP Session, Sender and Filter Spec objects, called LSP Tunnel IPv4 and LSP Tunnel IPv6 have been defined to support the LSP tunnel feature.

In some applications it is useful to associate sets of LSP tunnels, such as during reroute operations or in spreading a traffic trunk over multiple paths, which sets are called traffic engineered tunnels (TE tunnels). To enable the identification and association of the LSP tunnels, two identifiers 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. The Sender (or Filter Spec) object, together with the Session object, uniquely identify an LSP tunnel.

Protocol Structure - RSVP-TE Resource Reservation Protocol  - Traffic Extension Apart from the existing message types listed in RSVPan additional message type is available:

Message type

In addition, the following additional Protocol Object Types exist: 

Object type
Explicit Route
Record Route
Attribute Session