RSVP-TE Overview

RSVP is a protocol that defines procedures for signaling QoS (Quality of Service) 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 (Open Shortest Path First) 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 (Multiprotocol Label Switching) 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 (Virtual LAN) 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.

Published March 2020prev | next

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