MPLS and RSVP-TE
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MPLS Guide
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• retry-timer — the retry timer defines a period of time before a resignal attempt is
made after an LSP failure. This delay time protects network resources against
excessive signaling overhead.
3.4.1.3 LSP Resignal Limit
When an LSP fails, an LER node tries to resignal it. The following limit can be
configured:
• retry-limit — the retry limit defines the number of resignaling attempts in order to
conserve the resources of the nodes in the network. There could be a serious
loss of capacity due to a link failure where an infinite number of retries generate
unnecessary message overhead.
3.4.1.4 RSVP-TE Message Pacing
RSVP-TE message pacing provides a means to limit the overwhelming number of
RSVP-TE signaling messages that can occur in large MPLS networks during node
failures. RSVP-TE message pacing allows the messages to be sent in timed
intervals.
To protect nodes from receiving too many messages, the following message pacing
parameters can be configured:
• msg-pacing — message pacing can be enabled or disabled
• max-burst — maximum burst defines the number of RSVP-TE messages that
can be sent in the specified period of time
• period — period defines the interval of time used in conjunction with the max-
burst parameter to send message pacing RSVP-TE messages
Message pacing needs to be enabled on all the nodes in a network to ensure the
efficient operation of tier-1 nodes. Message pacing affects the number of RSVP-TE
messages that a particular node can generate, not the number of messages it can
receive. Therefore, each node must be paced at a rate that allows the most loaded
MPLS nodes to keep up with the number of messages they receive.
Note: Typically, a tier-1 node is an aggregator of tier-2 node transmissions, which is an
aggregator of tier-3 node transmissions. Tier-1 nodes are often installed at an MTSO, while
tier-3 nodes are often installed at cell sites.
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