Table of Contents
Advertisement
LDP over RSVP Without Area Boundary
The LDP over RSVP capability set includes the ability to stitch LDP-over-RSVP tunnels at
internal (non-ABR) OSPF and IS-IS routers.
In
Figure
"Dest". The first thing that happens is that either OSPF or IS-IS will perform an SPF calculation
resulting in an SPF tree. This tree specifies the lowest possible cost to the destination. In the
example shown, the destination "Dest" is reachable at the lowest cost through router X. The SPF
tree will have the following path: A>C>E>G>X.
Using this SPF tree, router A will search for the endpoint that is closest (farthest/highest cost from
the origin) to "Dest" that is eligible. Assuming that all LSPs in the above diagram are eligible,
LSP endpoint G will be selected as it terminates on router G while other LSPs only reach routers C
and E, respectively.
IGP and LSP metrics associated with the various LSP are ignores; only tunnel endpoint matters to
IGP. The endpoint that terminates closest to "Dest" (highest IGP path cost) will be selected for
further selection of the LDP over RSVP tunnels to that endpoint. Note that the explicit path the
tunnel takes may not match the IGP path the SPF computes.
7950 SR OS MPLS Configuration Guide
LSP1
A>B>D>F>G
20
B
25
A
LSP3
25
A>C
10
C
25
10
H
Figure 21: LDP over RSVP Without ABR Stitching Point
21, assume that the user wants to use LDP over RSVP between router A and destination
15
D
F
25
25
LSP2
A>C>E
10
20
E
G
20
K
Label Distribution Protocol
Link & IGP Cost
SPF PATH
X
Dest.
Page 347
Advertisement
Chapters
Table of Contents
