Re: [Idr] RtgDir review: draft-ietf-idr-add-paths-13

Alia Atlas <> Fri, 29 April 2016 20:30 UTC

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Date: Fri, 29 Apr 2016 16:30:55 -0400
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From: Alia Atlas <>
To: "Carlos Pignataro (cpignata)" <>
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Subject: Re: [Idr] RtgDir review: draft-ietf-idr-add-paths-13
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Hi Carlos,

Thank you very much for your review.

Shepherd & authors,

Could you please respond and update the draft ASAP with what you agree are
as well as addressing the one IETF Last Call comment with the agreed


On Wed, Apr 27, 2016 at 4:27 PM, Carlos Pignataro (cpignata) <>; wrote:

> Hello,
> I have been selected as the Routing Directorate reviewer for this
> draft. The Routing Directorate seeks to review all routing or
> routing-related drafts as they pass through IETF last call and IESG review,
> and sometimes on special request. The purpose of the review is to
> provide assistance to the Routing ADs. For more information about the
> Routing Directorate, please see ​
> Although these comments are primarily for the use of the Routing ADs,
> it would be helpful if you could consider them along with any other
> IETF Last Call comments that you receive, and strive to resolve them
> through discussion or by updating the draft.
> Document: draft-ietf-idr-add-paths-13
> Reviewer: Carlos Pignataro
> Review Date: April 25, 2016
> Intended Status: Proposed Standard
> Summary:
> This document is basically ready for publication, but has nits that should
> be considered prior to publication.
> Comments:
> This is an extremely well written document, very focused and with high
> SNR. I have a couple totally-non-critical comments and questions below.
> Major Issues:
> None.
> Minor Issues:
> I have a couple of questions rather than issues:
> 2.  How to Identify a Path
> ...
>    A BGP
>    speaker that receives a route SHOULD NOT assume that the identifier
>    carries any particular semantics; it SHOULD be treated as an opaque
>    value.
> I was thinking about why “SHOULD NOT” and not “MUST NOT”, and I understand
> future proofing, but wondering if there’s another reason.
> The path identifier has well-defined semantics: make a path unique for a
> given prefix, or make the {identifier; prefix} specify a path among many.
> Does this sentence intend to specify that a BGP receiving a route SHOULD
> NOT assume particular semantics of the numerical value of the field? (such
> as the lower value means a more important route), or SHOULD NOT assume
> particular semantics of the structure of the field? (such as some
> hierarchy, or MSB with some meaning). Or both?
> Maybe, “… assume that the value or structure of the identifier carries …”?
> Or maybe it is OK as is and I am reading too much into it?
> 6.  Applications
>    The BGP extension specified in this document can be used by a BGP
>    speaker to advertise multiple paths in certain applications.  The
>    availability of the additional paths can help reduce or eliminate
>    persistent route oscillations [RFC3345].  It can also help with
>    optimal routing and routing convergence in a network.  The
>    applications are detailed in separate documents.
> The final sentence does not seem to add anything, other than questions.
> I’d suggest either adding pointers to those separate documents, or removing
> the sentence. This is a non-normative section.
> 7.  Deployment Considerations
>    The extension proposed in this document provides a mechanism for a
>    BGP speaker to advertise multiple paths over a BGP session.  Care
>    needs to be taken in its deployment to ensure consistent routing and
>    forwarding in a network, the details of which will be described in
>    separate application documents.
> Similarly, which documents? These seem like important considerations.
> Nits:
> 4.  ADD-PATH Capability
>    The ADD-PATH Capability is a new BGP capability [RFC5492].  The
>    Capability Code for this capability is specified in the IANA
>    Considerations section of this document.
> Why not say "The ADD-PATH Capability is a new BGP capability [RFC5492],
> with Capability Code of 69” and simplify it for the reader?
> 9.  Security Considerations
> ...
>   The use of the ADD-PATH Capability is intended to
>    address specific needs related to, for example, eliminating the MED-
>    induced route oscillations in a network
>    [I-D.ietf-idr-route-oscillation-stop].  While the applications for
>    the ADD-PATH Capability are outside the scope of this document, the
>    users are encouraged to examine their behavior and potential impact
>    by studying the best practices described in
>    [I-D.ietf-idr-add-paths-guidelines].
> Are these Security Considerations, Applications, or Deployment
> Considerations?
> I hope these help,
> — Carlos.