Stewart
If you think that there are other problems that needs to be addressed,
do not attempt to push it down the throat of our draft. Instead put out
your own proposal. But make sure that it has enough merit to convince
the WG that it is better or more comprehensive instead of attempting to
point out fictitious problems in others' proposals.
Ahmed
On 8/7/2017 1:34 PM, Stewart Bryant wrote:
Ahmed,
The WG decides what is in or out of scope for a WG draft, and it does
this via the rough consensus of the WG, not the view of the authors.
Of course if you wish to refocus this as an independent draft and
submit via the ISE. If you do, you are welcome and I will leave you to it.
Meanwhile the draft really has to discuss SRLGs are they are in real
life, not as you would wish them to be.
Another type of false SRLG btw is when you are doing node protection
(you normally treat a node as an SRLG), but only a line interface has
failed.
- Stewart
On 07/08/2017 21:04, Ahmed Bashandy (bashandy) wrote:
Stewart
I already replied to Sikhi explaining the concept of the SRLG used in
this draft and the intent to make it even clearer.
IMO the scope of the draft is very clear from the draft itself as
well as the numerous responses during the previous IETF and the
mailing list.
The issue below is **out of scope** of the draft and hence I have no
plans on addressing it.
I hope you don’t insist on pushing out-of-scope topics down the
throat of this draft :)
Ahmed
*From:*Stewart Bryant [mailto:[email protected]]
*Sent:* Monday, August 07, 2017 12:48 PM
*To:* Ahmed Bashandy (bashandy); Stewart Bryant; Sikhivahan Gundu;
[email protected]
*Cc:* [email protected]; [email protected]
*Subject:* Re: I-D Action:
draft-bashandy-rtgwg-segment-routing-ti-lfa-01.txt
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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