Traffic Engineering; Rsvp Tunneling - Extreme Networks BlackDiamond 6800 MPLS Installation And User Manual

Configuring RSVP-TE
as topology changes that alter the routed path for a flow. However, the increased
control traffic load can be a scalability concern. For this reason, considerable work has
been done towards reducing RSVP refresh overhead through the implementation of
RFC 2961, RSVP Overhead Refresh Reduction Extensions. One aspect of RSVP refresh
reduction enables a very long refresh timer by adding support for reliable delivery of
RSVP control messages. Prior to refresh reduction, the refresh timer had to be relatively
short to ensure timely reservation establishment in the event of a dropped packet.
Further reductions are achieved through a mechanism called summary refresh, which
involves transmitting only the message identifiers associated with the RSVP messages
to be refreshed, instead of transmitting the entire unchanged contents of the RSVP
messages, and bundling the message identifiers for multiple refresh operations into a
single packet.

Traffic Engineering

This section describes RSVP traffic engineering and the following topics:
• RSVP Tunneling on page 5-8
• RSVP Objects on page 5-9

RSVP Tunneling

An RSVP tunnel sends traffic from an ingress node through an LSP. The traffic that
flows through the LSP is opaque (or tunneled) to the intermediate nodes along the path.
Traffic flowing through the tunnel to an intermediate node along the path is identified
by the previous hop and is forwarded, based on the label value(s), to the downstream
node.
RSVP tunnels can:
• Establish tunnels with or without QoS requirements.
• Dynamically reroute an established tunnel.
• Observe the actual route traversed by a tunnel.
• Identify and diagnose tunnels.
• Use administrative policy control to preempt an established tunnel.
• Perform downstream-on-demand label allocation, distribution, and binding.
5-8 MPLS Module Installation and User Guide