Re: [babel] ECMP routing
Juliusz Chroboczek <jch@irif.fr> Sat, 13 October 2018 11:45 UTC
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Date: Sat, 13 Oct 2018 13:44:40 +0200
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From: Juliusz Chroboczek <jch@irif.fr>
To: "STARK, BARBARA H" <bs7652@att.com>
Cc: "babel@ietf.org" <babel@ietf.org>, Acee Lindem <acee@cisco.com>
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Subject: Re: [babel] ECMP routing
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(Added Acee to CC, in case he has some useful thoughts on the subject.) > Juliusz once said on a babel thread "Of the multiple routes to a given > destination, at most one is selected." Is this a necessary condition > (due to the nature of Babel?) or is it simply that none of the > implementations do ECMP? RFC 6126bis does not allow ECMP. While Babel should in principle be able to be extended to do ECMP, doing that is not entirely obvious, for the following reasons: - it is not clear how to make the loop-avoidance algorithm interact with ECMP -- in concrete terms, what router-id and seqno to pick for an ECMP route; - since Babel uses dynamically computed metrics and hysteresis, the likelihood of multiple having exactly the same metric is fairly low; in practice, you'd need to balance over unequal-cost routes; - ECMP does not improve performance in all topologies; in fact, in many topologies, it decreases performance; hence, successful deployment of ECMP requires competent network administration, and it is not clear to me that Babel is being actively deployed in the kind of topologies where ECMP is worthwile. In short, ECMP in Babel is an open research problem -- I think it would make a good subject for a Master's degree, were it not for the last point above. Since the research has not been done yet, I think that it would be premature to consider ECMP in the information model. -- Juliusz
- [babel] ECMP routing STARK, BARBARA H
- Re: [babel] ECMP routing Juliusz Chroboczek
- Re: [babel] ECMP routing 7riw77
- Re: [babel] ECMP routing Juliusz Chroboczek
- Re: [babel] ECMP routing 7riw77
- Re: [babel] ECMP routing Acee Lindem (acee)
- Re: [babel] ECMP routing Juliusz Chroboczek
- Re: [babel] ECMP routing David Schinazi
- Re: [babel] ECMP routing STARK, BARBARA H
- Re: [babel] ECMP routing Toke Høiland-Jørgensen