Alcatel-Lucent 7450 Manual page 293

The GR Restart helper consists of a couple of phases. Once it loses Hello communication with its
neighbor, the helper node enters the Restart phase. During this phase, it preserves the state of all
RSVP sessions to its neighbor and waits for a new Hello message.
Once the Hello message is received indicating the restarting node preserved state, the helper node
enters the recovery phase in which it starts refreshing all the sessions that were preserved. The
restarting node will activate all the stale sessions that are refreshed by the helper node. Any Path state
which did not get a Resv message from the restarting node once the Recovery Phase time is over is
considered to have expired and is deleted by the helper node causing the proper Path Tear generation
downstream.
The duration of the restart phase (recovery phase) is equal to the minimum of the neighbor's
advertised Restart Time (Recovery Time) in its last Hello message and the locally configured value of
the max-restart (max-recovery) parameter.
When GR helper is enabled on an RSVP interface, its procedures apply to the state of both P2P and
P2MP RSVP LSP to a neighbor over this interface.
Default disable
graceful-shutdown
Syntax [no] graceful-shutdown
Context config>router>rsvp
config>router>rsvp>interface
Description This command initiates a graceful shutdown of the specified RSVP interface or all RSVP interfaces
on the node if applied at the RSVP level. These are referred to as maintenance interface and
maintenance node, respectively.
To initiate a graceful shutdown the maintenance node generates a PathErr message with a specific
error sub-code of Local Maintenance on TE Link required for each LSP that is exiting the
maintenance interface.
The node performs a single make-before-break attempt for all adaptive CSPF LSPs it originates and
LSP paths using the maintenance interfaces. If an alternative path for an affected LSP is not found,
then the LSP is maintained on its current path. The maintenance node also tears down and re-signals
any detour LSP path using listed maintenance interfaces as soon as they are not active.
The maintenance node floods an IGP TE LSA/LSP containing Link TLV for the links under graceful
shutdown with Traffic Engineering metric set to 0xffffffff and Unreserved Bandwidth parameter set
to zero (0).
A head-end LER node, upon receipt of the PathErr message performs a single make-before-break
attempt on the affected adaptive CSPF LSP. If an alternative path is not found, then the LSP is
maintained on its current path.
A node does not take any action on the paths of the following originating LSPs after receiving the
PathErr message:
7450 ESS MPLS Guide
a. An adaptive CSPF LSP for which the PathErr indicates a node address in the address list and
the node corresponds to the destination of the LSP. In this case, there are no alternative paths
which can be found.
MPLS and RSVP
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