Alcatel-Lucent 7450 Manual page 36

Label Switching Routers
Note that if the standby is SRLG enabled, and the active path is the standby, and the primary
comes up, this will immediately trigger a delayed retry MBB on the standby. If the delayed retry
MBB fails, immediate reversion to the primary will occur irrespective of the retry timer.
When the system reverts from a secondary standby or secondary path to the primary path, a
Delayed Retry MBB will be attempted to bring bandwidth of the standby path back to its
configured bandwidth. Delayed Retry MBB is attempted once, and if it fails, the standby will be
torn down. A Delayed Retry MBB has highest priority among all MBBs, so it will take precedence
over any other MBB in progress on the standby path (e.g. Config change or Preemption).
The system will carry-over the last signaled BW of the LSP over multiple failovers. For example,
if an LSP is configured with auto-BW for some time, and adjusts its currently reserved bandwidth
for the primary, and Monitor mode is then enabled, BW adjustment on the primary ceases, but the
BW remains reserved at the last adjusted value. Next, the LSP fails over to a secondary or
secondary standby. The secondary will inherit the last reserved BW of the primary, but then
disable further adjustment as long as monitoring mode is enabled.
Note that there are some caveats to the ability to carry-over the last signaled BW across failovers:
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Measurement of LSP Bandwidth
Automatic adjustment of RSVP LSP bandwidth based on measured traffic rate into the tunnel
requires the LSP to be configured for egress statistics collection at the ingress LER. The following
CLI shows an example:
config router mpls lsp name
egress-statistics
accounting-policy 99
collect-stats
no shutdown
exit
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Case 1: If the LSP fails over from path1 to path2 and the AutoBW MBB on path2 is
successful, then the last signaled BW is carried over when the LSP reverts back to path1 or
fails over to a new path3. This may trigger an AutoBW MBB on the new active path to
adjust its bandwidth to last signaled BW.
Case 2: If the LSP fails over from path1 to path2 and the AutoBW MBB on path2 is still in
progress and the LSP reverts back to path1 or fails over to a new path3, then the last
signaled BW is carried over to the new active path (path1 or path3) and this may result in
an AutoBW MBB on that path.
Case 3: If the LSP fails over from path1 to path2 and the AutoBW MBB on path2 fails
(after 5 retry attempts), the last signaled BW from when path1 was active is lost.
Therefore, when the LSP reverts back to path1 or fails over to a new path3, then the
original signaled BW from path1 is not carried over. However the signaled bandwidth of
path2 will be carried over to the new active path (path1 or path3) and may trigger an
AutoBW on that path.
7450 ESS MPLS Guide