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

Peter Psenak <> Mon, 20 November 2017 22:04 UTC

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Date: Mon, 20 Nov 2017 23:04:44 +0100
From: Peter Psenak <>
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Subject: Re: [Isis-wg] ISIS SR Flexible Algorithm (Resending with alias correction)
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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 


> Thanks,
> Acee