RE: Is TI-LFA compatible with the default SR algorithm?

Alexander Vainshtein <Alexander.Vainshtein@ecitele.com> Thu, 14 June 2018 13:58 UTC

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From: Alexander Vainshtein <Alexander.Vainshtein@ecitele.com>
To: Stewart Bryant <stewart.bryant@gmail.com>
CC: Michael Gorokhovsky <Michael.Gorokhovsky@ecitele.com>, "draft-ietf-spring-segment-routing.authors@ietf.org" <draft-ietf-spring-segment-routing.authors@ietf.org>, "spring@ietf.org" <spring@ietf.org>, "rtgwg@ietf.org" <rtgwg@ietf.org>, "stephane.litkowski@orange.com" <stephane.litkowski@orange.com>, "draft-bashandy-rtgwg-segment-routing-ti-lfa.authors@ietf.org" <draft-bashandy-rtgwg-segment-routing-ti-lfa.authors@ietf.org>
Subject: RE: Is TI-LFA compatible with the default SR algorithm?
Thread-Topic: Is TI-LFA compatible with the default SR algorithm?
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Date: Thu, 14 Jun 2018 13:58:40 +0000
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Stewart,
Lots of thanks for the clarification.

Coming back to the TI-LFA draft, I think that it should explicitly state that  in the case of Prefix-SIDs it is applicable to Prefix-SIDs associated with the  strict SPF algorithm but does not guarantee any results in the case of Prefix-SIDs associated with the default algorithm.

Regards,
Sasha

Office: +972-39266302
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Email:   Alexander.Vainshtein@ecitele.com

From: Stewart Bryant [mailto:stewart.bryant@gmail.com]
Sent: Thursday, June 14, 2018 3:59 PM
To: Alexander Vainshtein <Alexander.Vainshtein@ecitele.com>om>; stephane.litkowski@orange.com
Cc: Michael Gorokhovsky <Michael.Gorokhovsky@ecitele.com>om>; draft-ietf-spring-segment-routing.authors@ietf.org; spring@ietf.org; rtgwg@ietf.org; draft-bashandy-rtgwg-segment-routing-ti-lfa.authors@ietf.org
Subject: Re: Is TI-LFA compatible with the default SR algorithm?




On 14/06/2018 13:45, Alexander Vainshtein wrote:
Please note that RFC 5286 explicitly states that it is only applicable to intra-domain routing only with OSPF or IS-IS as IGP.
It does not mention the possibility of local policies overriding shortest path routing provided by these protocols.

10 years ago when we were thinking about these early IPFRR schemes I don't recall anyone considering anything
other that simple Dijkstra paths for IP. The exception perhaps was Not-Via, but in that case base connectivity
and repair had orthogonal address spaces. I am not sure is that is the direction with policy and flex, but
that may be a required direction for unconditional safety.

- Stewart

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