Stefano, Chris and all,
I have to admit that I am completely confused:
- to the best of my understanding, Chris has asked whether a policy
that puts a limit on max. number of ECMP next hops is not compatible with the
Strict SPF algorithm
- Stefano says that "Yes, this policy is a good example when Strict SPF
algorithm can be advertised".
What do I miss?
Regards,
Sasha
Office: +972-39266302
Cell: +972-549266302
Email: alexander.vainsht...@ecitele.com
-----Original Message-----
From: spring [mailto:spring-boun...@ietf.org] On Behalf Of Stefano Previdi
(sprevidi)
Sent: Monday, September 19, 2016 12:43 PM
To: Chris Bowers <cbow...@juniper.net>
Cc: spring@ietf.org
Subject: Re: [spring] meaning of "Strict Shortest Path" algorithm in
draft-ietf-spring-segment-routing-09
> On Sep 14, 2016, at 7:06 PM, Chris Bowers <cbow...@juniper.net> wrote:
>
> SPRING WG,
>
> The current text in draft-ietf-spring-segment-routing-09 regarding the
> "Strict Shortest Path" algorithm reads as follows.
>
> o "Strict Shortest Path": This algorithm mandates that the packet is
> forwarded according to ECMP-aware SPF algorithm and instruct any
> router in the path to ignore any possible local policy overriding
> SPF decision. The SID advertised with "Strict Shortest Path"
> algorithm ensures that the path the packet is going to take is the
> expected, and not altered, SPF path.
>
> One example of a local policy that overrides the ECMP-aware SPF
> algorithm decision is a limit on the number of ECMP next-hops. The
> text above implies that if a router places any limit on the number of
> ECMP forwarding next-hops then it would be wrong for it to advertise the
> “Strict Shortest Path” algorithm capability.
>
> Is this the intended interpretation?
well, yes. Your example is a good one for the “strict-SPF” behavior.
s.
>
> If not, what is the intended interpretation?
>
> Thanks,
> Chris
>
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> spring@ietf.org
> https://www.ietf.org/mailman/listinfo/spring
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