RSVP is a network control protocol that enables Internet applications to
signal LSPs for MPLS-TE
RSVP implementation is compliant with the IETF RFC 2205,
RSVP is automatically enabled on interfaces on which MPLS-TE is
configured. For MPLS-TE LSPs with nonzero bandwidth, the RSVP bandwidth has to
be configured on the interfaces. There is no need to configure RSVP, if all
MPLS-TE LSPs have zero bandwidth
RSVP Refresh Reduction, defined in RFC 2961, includes support for
reliable messages and summary refresh messages. Reliable messages are
retransmitted rapidly if the message is lost. Because each summary refresh
message contains information to refresh multiple states, this greatly reduces
the amount of messaging needed to refresh states. For refresh reduction to be
used between two routers, it must be enabled on both routers. Refresh Reduction
is enabled by default.
Message rate limiting for RSVP allows you to set a maximum threshold on
the rate at which RSVP messages are sent on an interface. Message rate limiting
is disabled by default.
The process that implements RSVP is restartable. A software upgrade,
process placement or process failure of RSVP or any of its collaborators, has
been designed to ensure Nonstop Forwarding (NSF) of the data plane.
RSVP supports graceful restart, which is compliant with RFC 3473. It
follows the procedures that apply when the node reestablishes communication
with the neighbor’s control plane within a configured restart time.
It is important to note that RSVP is not a routing protocol. RSVP works
in conjunction with routing protocols and installs the equivalent of dynamic
access lists along the routes that routing protocols calculate. Because of
this, implementing RSVP in an existing network does not require migration to a
new routing protocol.
For IOS-XR versions prior to 6.3.2, only up to 600 LDP sessions were possible over RSVP-TE tunnels on Cisco ASR 9000 series
routers. Effective with Cisco IOS-XR release 6.3.2, the number of LDP sessions possible over RSVP-TE tunnels is increased