The MPLS WG Archive

["zze-PELLE Thierry StagiaireFTRD/DAC/ISS" <thierry.pelle@rd.francetelecom.fr>]

HI,
> hi!
>      IMHO this is not correct as the LSR from which the label
> mapping has beeen
> learnt can never be the upstream LSR for the same mapping - liberal or
> conservative mode notwithstanding.

Even if the IGP completely change the route for the FEC?

e.g.

If the network is           -------
                           /       \
                     A----B----C----D
				       |    |
                               \----E


First, the Path from A to E may be A B C D E. In this case,
                            -------
                           /       \
                     A-->-B-->-C-->-D
				       |   \|/
                               \----E
hence, C is upstream with respect to D : C uses the label distributed by D.

If the path from A to E changed to A B D C E. In this case,
                            --->---
                           /       \
                     A-->-B----C--<-D
				       \|/  |
                               \----E
here, D is upstream with respect to C : D uses the label distributed by C.

Finally, in liberal mode, if C has distributed a label to D (in the first
case, where D was the Next Hop for C), it can use it directly.

This is a quite strange case but it seems to be ok.

Thierry