Chapter 4 Implementing Rsvp For Mpls-Te; Implementing Rsvp For Mpls-Te; Setting Up Mpls Lsp Using Rsvp - Cisco NCS 5500 Series Configuration Manual

Implementing RSVP for MPLS-TE

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Implementing RSVP for MPLS-TE
Resource Reservation Protocol (RSVP) is a signaling protocol that enables systems to request resource
reservations from the network. RSVP processes protocol messages from other systems, processes resource
requests from local clients, and generates protocol messages. As a result, resources are reserved for data flows
on behalf of local and remote clients. RSVP creates, maintains, and deletes these resource reservations.
MPLS Traffic Engineering (MPLS-TE) learns the topology and resources available in a network and then
maps traffic flows to particular paths based on resource requirements and network resources such as bandwidth.
MPLS TE builds a unidirectional tunnel from a source to a destination in the form of a label switched path
(LSP), which is then used to forward traffic. MPLS-TE uses RSVP to signal LSPs.

Setting up MPLS LSP Using RSVP

The following figure shows how RSVP sets up a LSP from router R1 through router R4 that can be used for
TE in an MPLS environment.
Figure 6: MPLS LSP Using RSVP
The LSP setup is initiated when the LSP head node sends path messages to the tail node. The Path messages
reserve resources along the path to each node, and creates path states associated with the session on each node.
When the tail node receives a path message, it sends a reservation (RESV) message with a label back to the
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MPLS Configuration Guide for Cisco NCS 5500 Series Routers, IOS XR Release 6.2.x
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