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Re: [spring] draft-hu-spring-segment-routing-proxy-forwarding-14: Post convergence path

Stewart Bryant <stewart.bryant@gmail.com> Mon, 26 July 2021 20:22 UTC

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From: Stewart Bryant <stewart.bryant@gmail.com>
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Date: Mon, 26 Jul 2021 21:22:49 +0100
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Cc: Stewart Bryant <stewart.bryant@gmail.com>, "spring@ietf.org" <spring@ietf.org>
To: Shraddha Hegde <shraddha=40juniper.net@dmarc.ietf.org>
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Subject: Re: [spring] draft-hu-spring-segment-routing-proxy-forwarding-14: Post convergence path
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Isn’t the point about TI-LFA that it re-routes on the post convergence path to avoid micro-loops. 

When you overestimate the failure to provide node protection even though the failure was not a node failure, the repair path may not be congruent with the post convergence path in which case you need to understand if micro loops will form in the specific topology for the specific failure.

- Stewart

> On 26 Jul 2021, at 21:16, Shraddha Hegde <shraddha=40juniper.net@dmarc.ietf.org> wrote:
> 
> WG,
>  
> Regarding Peter’s comment on the mic that TI-LFA can divert from post convergence path when SRLG
> is used for computation I would like to clarify that an operator is expected to do
> planning for the post convergence path accounting for the SRLG failures.
>  
> draft-hu-spring-segment-routing-proxy-forwarding-14 is proposing a mechanism which will
> divert the traffic based on nodes being upgraded to support the protection. The paths
> could be quite divergent from post-convergence path and an operator would be expected
> to do planning to ensure these paths have sufficient bandwidth to take on traffic.
>  
> Rgds
> Shraddha
> 
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