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MPLS Guide
3.4.1.5
RFC 2961, RSVP Refresh Overhead Reduction Extensions, defines enhancements
to the RSVP-TE signaling protocol that reduce refresh overhead, which are in
addition to the message pacing function.
These extensions are:
These capabilities can be enabled on a per-RSVP-TE interface basis and are
referred to collectively as "refresh overhead reduction extensions". When refresh-
reduction is enabled on a 7705 SAR RSVP-TE interface, the node indicates this to
its peer by setting a refresh-reduction-capable bit in the flags field of the common
RSVP-TE header. If both peers of an RSVP-TE interface set this bit, all three of the
capabilities listed above can be used. The node monitors the setting of this bit in
received RSVP-TE messages from the peer on the interface. If the bit is cleared, the
node stops sending summary refresh messages. If a peer did not set the refresh-
reduction-capable bit, a 7705 SAR node does not attempt to send summary refresh
messages.
Also, reliable delivery of RSVP-TE messages over the RSVP-TE interface can be
enabled using the reliable-delivery option.
3HE 18686 AAAB TQZZA
RSVP-TE Overhead Refresh Reduction
• RSVP-TE message bundling — RSVP-TE message bundling reduces the total
number of RSVP-TE messages by aggregating the status information of multiple
LSPs into a single RSVP-TE PDU. The 7705 SAR supports the receipt and
processing of bundled RSVP-TE messages but not the transmission of bundled
messages as specified in RFC 2961, section 3.3.
• reliable message delivery — reliable message delivery extends RSVP-TE to
support MESSAGE_ACK. Each RSVP-TE PDU has a unique message-id for
sequence tracking purposes. When an RSVP-TE message arrives, the recipient
acknowledges the reception of the specific message-id (this is similar to TCP
ACK messages). Lost PDUs can be detected and re-sent with this method,
which helps reduce the refresh rate because there are two endpoints tracking
the received/lost messages.
• summary refresh — the summary refresh capability uses a single message-id
list to replace many individual refresh messages and sends negative ACKs
(NACKs) for any message-id that cannot be matched (verified). The summary
refresh capability reduces the number of message exchanges and message
processing between peers. It does not reduce the amount of soft state stored in
the node. The term soft state refers to the control state in hosts and routers that
will expire if not refreshed within a specified amount of time (see RFC 2205 for
information on soft state).
Use subject to Terms available at: www.nokia.com
© 2022 Nokia.
MPLS and RSVP-TE
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