Subject: [RTG-DIR] RtgDir Last Call Review: draft-ietf-babel-source-specific-06

From: "Hejia (Jia)" <[email-masked]>
Date: Tue, 27 Oct 2020 16:06:56 +0000

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 http://trac.tools.ietf.org/area/rtg/trac/wiki/RtgDir

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-babel-source-specific-06.txt
Reviewer: Jia He
Review Date: Oct. 27, 2020
IETF LC End Date: date-if-known
Intended Status: Standards Track

Summary:

This document is basically ready for publication, but I have one minor concern that I think should be considered before publication.

Comments:

The draft is clearly writtern and easy to understand. It describes the extensions to the Babel routing protocol to support source-specific routing.

Major Issues:

No major issues found.

Minor Issues:

In Paragraph 5, it is written as

"In the original protocol, three TLVs carry a destination prefix:
   Updates, Route Requests and Seqno Requests.  This specification
   extends these messages to optionally carry a Source Prefix sub-TLV,
   as described in Section 7 below.  The sub-TLV is marked as mandatory,
   so that an unextended implementation will silently ignore the whole
   enclosing TLV. "

I understand the the Source Prefix sub-TLV is mandatory to support the functions defined in this specification.  However, "optionally" used in the paragraph above is confusing. One suggestion is to simply delete "optionally" in the sentence.

B.R.

Jia

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From: Juliusz Chroboczek <[email-masked]>
Date: Wed, 28 Oct 2020 15:06:07 +0100

>    This specification
>    [...]
>    The sub-TLV is marked as mandatory,

> I understand the the Source Prefix sub-TLV is mandatory to support the
> functions defined in this specification.  However, "optionally" used in
> the paragraph above is confusing. One suggestion is to simply delete
> "optionally" in the sentence.

I most respectfully disagree.  The sub-TLV is optional -- non-specific
routes don't carry the sub-TLV, which is the whole reason why the
extension interoperates with unextended Babel.  This is expanded upon in
Section 5:

   A node obeying this specification MUST NOT send a TLV
   with a zero-length source prefix: instead, it sends a TLV with no
   Source Prefix sub-TLV.

I think it's important to stress this fact in this paragraph.  I've
avoided the term "optional", which I believe is what you're objecting to:

   This specification extends these messages so that they may carry
   a Source Prefix sub-TLV,

I don't like the formulation very much, so I'll be grateful if you can
find a better wording.

-- Juliusz

---

From: Gabriel Kerneis <[email-masked]>
Date: Thu, 29 Oct 2020 17:12:41 +0100

> I don't like the formulation very much, so I'll be grateful if you can
Suggestion:
"This specification extends these messages to allow them to carry …"

Gabriel