Ldp Graceful Handling Of Resource Exhaustion; Ldp Base Graceful Handling Of Resources - Alcatel-Lucent 7450 Manual

LDP Graceful Handling of Resource Exhaustion

This feature enhances the behavior of LDP when a data path or a CPM resource required for the
resolution of a FEC is exhausted. In prior releases, the LDP module shuts down. The user is
required to fix the issue causing the FEC scaling to be exceeded and to restart the LDP module by
executing the unshut command.

LDP Base Graceful Handling of Resources

This feature implements a base graceful handling capability by which the LDP interface to the
peer, or the targeted peer in the case of Targeted LDP (T-LDP) session, is shutdown. If LDP tries
to resolve a FEC over a link or a targeted LDP session and it runs out of data path or CPM
resources, it will bring down that interface or targeted peer which will bring down the Hello
adjacency over that interface to the resolved link LDP peer or to the targeted peer. The interface is
brought down in LDP context only and is still available to other applications such as IP forwarding
and RSVP LSP forwarding.
Depending of what type of resource was exhausted, the scope of the action taken by LDP will be
different. Some resource such as NHLFE have interface local impact, meaning that only the
interface to the downstream LSR which advertised the label is shutdown. Some resources such as
ILM have global impact, meaning that they will impact every downstream peer or targeted peer
which advertised the FEC to the node. The following are examples to illustrate this.
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7450 ESS MPLS Guide
For NHLFE exhaustion, one or more interfaces or targeted peers, if the FEC is ECMP,
will be shut down. ILM is maintained as long as there is at least one downstream for the
FEC for which the NHLFE has been successfully programmed.
For an exhaustion of an ILM for a unicast LDP FEC, all interfaces to peers or all target
peers which sent the FEC will be shutdown. No deprogramming of data path is required
since FEC is not programmed.
An exhaustion of ILM for an mLDP FEC can happen during primary ILM programming,
MBB ILM programming, or multicast upstream FRR backup ILM programming. In all
cases, the P2MP index for the mLDP tree is deprogrammed and the interfaces to each
downstream peer which sent a Label Mapping message associated with this ILM are
shutdown.
Label Distribution Protocol
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