Stitching In The Ldp-To-Sr Direction; Figure 23 Stitching In The Ldp-To-Sr Direction - Nokia 7705 SAR-W Series Manual

Label Distribution Protocol
The sections that follow describe how stitching is performed in the LDP-to-SR and
SR-to-LDP data path directions.
5.1.14.1
Stitching in the data plane in the LDP-to-SR direction is based on the LDP module
monitoring the TTM for an SR tunnel of a prefix matching an entry in the LDP TTM
export policy.
Figure 23
In
domain and is configured to stitch between SR and LDP. Link R1-R2 is LDP-enabled,
but router R2 does not support SR or SR is disabled.
The following steps are performed by the boundary router R1 to configure stitching:
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Stitching in the LDP-to-SR Direction

Stitching in the LDP-to-SR Direction
SR Domain
Prefix Y,
Node SID = 20
Ry
Figure 23, router R1 is at the boundary between an SR domain and an LDP
1. Router R1 receives a prefix SID sub-TLV in an IS-IS IP reachability TLV
originated by router Ry for prefix Y.
2. R1 resolves the prefix SID and programs an NHLFE on the link toward the next
hop in the SR domain. R1 programs an SR ILM and points it to the NHLFE.
3. Because R1 is programmed to stitch LDP to SR, LDP in R1 checks the TTM and
finds the SR tunnel to prefix Y. LDP programs an LDP ILM and points it to the
SR tunnel. As a result, both the SR ILM and LDP ILM are now pointing to the SR
tunnel, one via the SR NHLFE and the other via the SR tunnel endpoint.
4. R1 advertises the LDP FEC for prefix Y to all its LDP peers. R2 is now able to
install an LDP tunnel towards Ry.
Use subject to Terms available at: www.nokia.com
LDP Domain
R1
Mapping Server
R5
Prefix Y, SID = 20
R3
© 2022 Nokia.
MPLS Guide
R2
Prefix X, LDP
Label = 5135
Rx
R4
28744
3HE 18686 AAAB TQZZA