Re: [Isis-wg] ISIS SR Flexible Algorithm (Resending with alias correction)

"Acee Lindem (acee)" <acee@cisco.com> Mon, 20 November 2017 22:31 UTC

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From: "Acee Lindem (acee)" <acee@cisco.com>
To: "Peter Psenak (ppsenak)" <ppsenak@cisco.com>, "draft-hegdeppsenak-isis-sr-flex-algo@ietf.org" <draft-hegdeppsenak-isis-sr-flex-algo@ietf.org>
CC: "isis-wg@ietf.org" <isis-wg@ietf.org>
Thread-Topic: ISIS SR Flexible Algorithm (Resending with alias correction)
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Date: Mon, 20 Nov 2017 22:31:07 +0000
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Subject: Re: [Isis-wg] ISIS SR Flexible Algorithm (Resending with alias correction)
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Hi Peter, 
At the edge of the SR domain, how does the ingress decide which
algorithm’s prefix SID to use? I guess it is a local matter. However, I
would call this out in the document.
Thanks,
Acee 

On 11/20/17, 5:04 PM, "Peter Psenak (ppsenak)" <ppsenak@cisco.com> wrote:

>Hi Acee,
>
>On 20/11/17 19:19 , Acee Lindem (acee) wrote:
>> Hi Shraddha, Peter, et al,
>>
>> The comment on the draft I had was that the conflict case where two ISIS
>> routers advertise the same multi-homed prefix with a different algorithm
>> needs to be covered. I wouldn’t try and optimize for this and would just
>> do whatever is simplest but avoids loops (e.g., log the situation and
>> prefer the path computed with the lowest numbered algorithm).
>
>prefix can have SIDs for many algorithms. Prefix-SID for one algorithm
>is independent and orthogonal to prefix-SID for any other algorithm.
>
>There is no need for all sources of the multi-homed prefix to include
>the same set of Algo-SIDs. Each source can advertise an independent set.
>
>The case is similar to Alg-0 SID, where prefix is advertised from two
>different sources and one source advertise the Alg-0 SID and other does
>not.
>
>thanks,
>Peter
>
>>
>> Thanks,
>> Acee
>