Local Protection - Nokia 7705 SAR-W Series Manual

MPLS Guide
The adjacency SID hold timer is not activated if the user deletes an interface in the
config>router>ospf/isis context.
Note:
While protection is enabled globally for all node SIDs and local adjacency SIDs when
the user enables the loopfree-alternates command in IS-IS or OSPF at the LER and
LSR, there are applications where the user wants traffic to never divert from the strict
hop computed by CSPF for an SR-TE LSP. In that case, the user can disable
protection for all adjacency SIDs formed over a particular network IP interface using
the sid-protection command.
The protection state of an adjacency SID is advertised in the B-FLAG of the IS-IS or
OSPF Adjacency SID sub-TLV. No mechanism exists in PCEP for the PCC to signal
to the PCE the constraint to use only adjacency SIDs, which are not protected. The
path profile ID is configured in the PCE with the no-protection constraint.
3.12.5.1
Each path can be locally protected through the network using LFA, remote LFA, or
TI-LFA next hop whenever possible. The protection of a node SID reuses the LFA
and remote LFA features introduced with SR shortest path tunnels. The protection of
an adjacency SID has been added to the 7705 SAR in the specific context of an SR-
TE LSP to augment the protection level. The user must enable the LFA, remote LFA,
or TI-LFA option in IS-IS or OSPF.
3HE 18686 AAAB TQZZA
• the user shuts down the network IP interface in the config>router or
config>router>ospf/isis context
• The adjacency SID hold timer does not apply to the ILM or LTN of a node SID, because
NHLFE information is updated in the data path as soon as the IGP is converged locally
and a new primary and LFA backup next hops have been computed.
• The label information of the primary path of the adjacency SID is maintained and
reprogrammed if the adjacency is restored before the timer expires. However, the
backup NHLFE may change when a new LFA SPF is run while the adjacency ILM is
being held by the timer running. An update to the backup NHLFE is performed
immediately following the LFA SPF and may cause packets to drop.
• A new protect group ID (PG-ID) is assigned each time an adjacency comes back up.
This PG-ID is used by the ILM of the adjacency SID and the ILMs of all downstream
node SIDs that resolve to the same next hop.

Local Protection

Use subject to Terms available at: www.nokia.com
© 2022 Nokia.
MPLS and RSVP-TE
107