Alcatel-Lucent 7450 Manual page 119

•
•
•
•
•
This feature is not supported on a P2MP LSP.
7450 ESS MPLS Guide
→ If the user changes the LSP level CT, all paths of the LSP are torn down and re-
signaled in a break-before-make fashion. Specifically, the LSP primary path will be
torn down and re-signaled even if it is currently using the backup CT.
→ If the user changes the main CT of the LSP primary path, the path will be torn down
and re-signaled even if it is currently using the backup CT.
→ If the user changes the backup CT of an LSP primary path when the backup CT is in
use, the path is torn down and is re-signaled.
→ If the user changes the backup CT of an LSP primary path when the backup CT is not
in use, no action is taken. If however, the path was in global Revertive, gshut, or soft
pre-emption MBB, the MBB is restarted. This actually means the first attempt will be
with the main CT and subsequent ones, if any, with the new value of the backup CT.
→ Consider the following priority of the various MBB types form highest to lowest:
Delayed Retry, Preemption, Global Revertive, Configuration Change, and TE
Graceful Shutdown. If an MBB request occurs while a higher priority MBB is in
progress, the latter MBB will be restarted. This actually means the first attempt will
be with the main CT and subsequent ones, if any, with the new value of the backup
CT.
If the least-fill option is enabled at the LSP level, then CSPF must use least-fill equal cost
path selection when the main or backup CT is used on the primary path.
When the re-signal timer expires, CSPF will try to find a path with the main CT. The
head-end node must re-signal the LSP even if the new path found by CSPF is identical to
the existing one since the idea is to restore the main CT for the primary path. If a path with
main CT is not found, the LSP remains on its current primary path using the backup CT.
This means that the LSP primary path with the backup CT may no longer be the most
optimal one. Furthermore, if the least-fill option was enabled at the LSP level, CSPF will
not check if there is a more optimal path, with the backup CT, according to the least-fill
criterion and will thus raise no trap to indicate the LSP path is eligible for least-fill re-
optimization.
When the user performs a manual re-signal of the primary path, CSPF will try to find a
path with the main CT. The head-end node must re-signal the LSP as in current
implementation.
If a CPM switchover occurs while an the LSP primary path was in retry using the main or
backup CT, for example, was still in operationally down state, the path retry will be
restarted with the main CT until it comes up. This is because the LSP path retry count is
not synchronized between the active and standby CPMs until the path becomes up.
When the user configured secondary standby and non-standby paths on the same LSP, the
switchover behavior between primary and secondary is the same as in existing
implementation.
MPLS and RSVP
Page 119