Table of Contents
Advertisement
MPLS and RSVP-TE
Figure 7
In order for a PLR within the local area of the ingress LER to provide ABR protection,
it must dynamically signal a bypass LSP and associate it with the primary path of the
inter-area LSP using the following procedures.
66
ABR Protection Using Dynamic Bypass LSP
ABR1_2
ERO: ABR1_2[S],P2[L]
XRO: ABR1_1
P1 -
PLR
PE1
LSP path empty Computed ERO:
P1[S], ABR1_1[S], PE2[L]
Legend:
[S]
Strict Hop
[L]
Loose Hop
• The PLR must inspect the RRO node-id of the LSP primary path to determine
the address of the node immediately downstream of the ABR in the other area.
• The PLR signals an inter-area bypass LSP with a destination address set to the
address downstream of the ABR and with the exclude route object (XRO) set to
exclude the node-id of the protected ABR.
• The request to CSPF is for a path to the merge point (that is, the next-next-hop
in the RRO received in the RESV message for the primary path) along with the
constraint to exclude the protected ABR and the include/exclude admin groups
of the primary path. If CSPF returns a path that can only go to an intermediate
hop, then the PLR signals the dynamic bypass and automatically includes the
XRO with the address of the protected ABR and propagates the admin-group
constraints of the primary path into the Session Attribute object of the bypass
LSP. Otherwise, the PLR signals the dynamic bypass directly to the merge point
node with no XRO in the PATH message.
Use subject to Terms available at: www.nokia.com
P2 -
Merge
Point
ABR2_1
ERO: P3[S],
PE2[S]
ABR1_1
ERO: P2[S],
ABR2_1[S],
PE2[L]
© 2022 Nokia.
MPLS Guide
P3
PE2
25053
3HE 18686 AAAB TQZZA
Advertisement
Table of Contents
