3Com MSR 50 Series, Руководство по настройке

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MPLS TE Overview 1353
refreshing mechanism was extended in RFC 2961 RSVP Refresh Overhead
Reduction Extensions as follows to address the problems:
1
Message_ID extension
RSVP itself uses Raw IP to send messages. The Message_ID extension mechanism
defined in RFC 2961 adds objects that can be carried in RSVP messages. Of them,
the Message_ID object and the Message_ID_ACK object are used to acknowledge
RSVP messages, thus improving transmission reliability.
On an interface enabled with the Message_ID mechanism, you may configure
RSVP message retransmission. After the interface sends an RSVP message, it waits
for an acknowledgement. If no ACK is received before the initial retransmission
interval (Rf seconds for example) expires, the interface resends the message. After
that, the interface resends the message at an exponentially increased
retransmission interval equivalent to (1 + Delta)
×
Rf seconds.
2
Summary refresh extension
Send summary refreshes (Srefreshes) rather than retransmit standard Path or Resv
messages to refresh related RSVP state. This reduces refresh traffic and allows
nodes to make faster processing.
To use summary refresh, you must use the Message_ID extension. Only states
advertised using MESSAGE_ID included Path and Resv messages can be refreshed
using summary refreshes.
PSB, RSB and BSB timeouts
To create an LSP tunnel, the sender sends a LABEL_REQUEST object with a Path
message. After receiving this Path message, the receiver assigns a label for the
path and put the label binding in the LABEL object in the returned Resv message.
The LABEL_REQUEST object is stored in the path state blocks (PSBs) on the
upstream nodes, while the LABEL object is stored in the reservation state blocks
(RSBs) on the downstream nodes. The state stored in the PSB or RSB object times
out and is removed after the number of consecutive non-refreshing times exceeds
the PSB or RSB timeout keep-multiplier.
You may sometimes want to store the resource reservation state for a reservation
request that does not pass the admission control on some node. This however
should not prevent the resources reserved for the request from being used by
other requests. To handle this situation, the node transit to the blockade state and
a blockade state block (BSB) is created on each downstream node. When the
number of non-refreshing times exceeds the blockade multiplier, the state in the
BSB is removed.
RSVP-TE GR
n
For introduction to Graceful Restart (GR), refer to “GR Overview” on page 1957 .
The RSVP-TE GR function depends on the extended hello capability of RSVP-TE.
That is why you need to enable the latter before configuring RSVP-TE GR.