RSVP-TE Overview

RSVP is a protocol that defines procedures for signaling QoS requirements and reserving the necessary resources for a router to provide a requested service to all nodes along a data path. This release supports inter-area RSVP tunnels.

Note

Partial path computation for FRR over multiple OSPF areas is not supported.

RSVP is not a routing protocol. It works in conjunction with unicast and multicast routing protocols. An RSVP process consults a local routing database to obtain routing information. Routing protocols determine where packets get forwarded; RSVP is concerned with the QoS of those packets that are forwarded in accordance with the routing protocol.

Reservation requests for a flow follow the same path through the network as the data comprising the flow. RSVP reservations are unidirectional in nature, and the source initiates the reservation procedure by transmitting a path message containing a traffic specification (Tspec) object. The Tspec describes the source traffic characteristics in terms of peak data rate, average data rate, burst size, and minimum/maximum packet sizes.

RSVP-TE is a set of traffic engineering extensions to RSVP. RSVP-TE extensions enable RSVP use for traffic engineering in MPLS environments. The primary extensions add support for assigning MPLS labels and specifying explicit paths as a sequence of loose and strict routes. These extensions are supported by including label request and explicit route objects in the path message. A destination responds to a label request by including a label object in its reserve message. Labels are then subsequently assigned at each node the reserve message traverses. Thus, RSVP-TE operates in downstream-on-demand label advertisement mode with ordered LSP control.

The ExtremeXOS software implementation of RSVP-TE complies with RFC 3209 and includes support for:

• Configuration on a per VLAN interface.

• Operation as either edge or core MPLS router.

• Support for specifying explicitly routed paths.

• Support for both loose and strict route objects.

• Recording the route of an established path.

• Bandwidth reservation and policy per LSP.

• Signaling QoS along the RSVP path using the Tspec and Adspec objects.

• Fixed Filter (FF) and Shared Explicit (SE) reservation styles.

• Specifying RSVP-TE session attributes.

• Scaling enhancements using Refresh Overhead Reduction extensions.

• Improved link failure detection using the RSVP-TE Hello Message.

• Ability to reroute traffic over pre-configured backup LSPs.