RE: Deborah Brungard's Discuss on draft-ietf-rtgwg-backoff-algo-07: (with DISCUSS)

"BRUNGARD, DEBORAH A" <> Sat, 24 February 2018 21:07 UTC

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To: "Acee Lindem (acee)" <>, The IESG <>
CC: "" <>, Uma Chunduri <>, "" <>, "" <>
Subject: RE: Deborah Brungard's Discuss on draft-ietf-rtgwg-backoff-algo-07: (with DISCUSS)
Thread-Topic: Deborah Brungard's Discuss on draft-ietf-rtgwg-backoff-algo-07: (with DISCUSS)
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Date: Sat, 24 Feb 2018 21:07:34 +0000
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Hi Acee,

Sorry for not responding earlier, I had an unexpected disruption to my schedule these last days.

I was concerned as the document itself says "Optionally, implementations may also offer alternative algorithms." So it is not clear if it is the algorithm or the parameters which are intended PS.

And especially concerning is section 7 on partial deployment. It states the algorithm is only effective if it is deployed on all routers, and partial deployment will increase the frequency and duration of micro-loops. It does go on to say operators have progressively replaced an implementation of a given algorithm by a different one.

If this is to be PS, then you need to provide guidance on how an operator is to do the upgrade to this new algorithm on a network. I understand there are prototype implementations, but I'm concerned on field grade deployments in existing networks.


-----Original Message-----
From: Acee Lindem (acee) [] 
Sent: Wednesday, February 21, 2018 7:53 PM
Cc:; Uma Chunduri <>om>;;
Subject: Re: Deborah Brungard's Discuss on draft-ietf-rtgwg-backoff-algo-07: (with DISCUSS)

Hi Deborah, 

Given that the goal of RFC 6976 was much more ambitious and the mechanisms are much more complex, I don't think this draft should be put in the same category. 

What we have done is precisely specify a standard algorithm for IGP SPF back-off. When deployed, this standard algorithm will greatly improve (but not eliminate) micro-loops in IGP routing domains currently utilizing disparate SPF back-off algorithms. The problem statement draft best articulates the impact of differing SPF back-off algorithms: . Finally, there have been several prototype implementations validating the algorithm specification's completeness and clarity. 



    Deborah Brungard has entered the following ballot position for

    draft-ietf-rtgwg-backoff-algo-07: Discuss


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    While I agree with Alvaro's concerns, my concern is the appropriateness of this document as PS.

    This document should have a similar status as RFC6976 (Informational) which also provided a

    mechanism that prevented transient loops saying "the mechanisms described in this

    document are purely illustrative of the general approach and do not constitute a protocol

    specification". Especially as this document compares itself to RFC6976, saying RFC6976 is a

    "full solution".


    With a change of status to Informational, this document would be better

    scoped as providing guidance vs. a specification.