Your answer did not address the issue below, which is one of a class of
issues related to SRLG.
- Stewart
On 07/08/2017 19:23, Ahmed Bashandy (bashandy) wrote:
See my reply to Sikhi
Thanks
Ahmed
On 8/7/2017 2:13 AM, Stewart Bryant wrote:
On 07/08/2017 06:45, Sikhivahan Gundu wrote:
By “ambiguity”, I meant that backup calculation taking SRLG into
account is based on speculated topology, whereas computation of
post-convergence path, ie, SPF, is based on actual topology. This
seems needs reconciling since in TI-LFA the backup is by definition
the post-convergence path, with a single path-transition after
link-failure as the intended outcome. Do I understand correctly that
the draft prefers to relax that expectation for SRLG?
Yes, that is a good point, in the event of an incomplete failure
of an SRLG, there may not be congruence between the
FRR path and the post convergence path. This certainly
needs further study.
*
A--------//---------B
| |
| * | cost 2
C-------------------D
| |
| | cost 100
E-------------------F
AB + CD in same SRLG
TiLFA path is ACEFDB
Post convergence path is ACDB
In this case I think that the impact is just more SR hops in the
repair path than might be needed without the SRLG, but we do need to
be sure that there are no pathological cases in
topologies that lack the proposed congruence, and as
Sikhivahan notes this effect does need to be clarified in the
text.
- Stewart
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