Re: [alto] Review of draft-ietf-alto-path-vector-11

"Y. Richard Yang" <yry@cs.yale.edu> Mon, 02 November 2020 22:04 UTC

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From: "Y. Richard Yang" <yry@cs.yale.edu>
Date: Mon, 02 Nov 2020 17:04:06 -0500
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To: LUIS MIGUEL CONTRERAS MURILLO <luismiguel.contrerasmurillo@telefonica.com>
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Subject: Re: [alto] Review of draft-ietf-alto-path-vector-11
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H Luis,

Thanks a lot for the wonderful review! As we upload the revision, here is a
summary of the changes that we make. Please see inline to see if you are
OK. After you approve, we will finalize all.

On Sun, Oct 25, 2020 at 5:01 PM LUIS MIGUEL CONTRERAS MURILLO <
luismiguel.contrerasmurillo@telefonica.com> wrote:

> Hi all,
>
>
>
> I have performed a review of the draft, with comments as follows:
>
>
>
> /* Technical comments */
>
> .- Section III Terminology – Path Vector bullet. Please, rephrase the
> description, it is hard to understand, especially the second sentence. Not
> clear.
>

OLD
 Path Vector: A Path Vector, or an ANE Path Vector, is a JSON array
      of ANE Names.  It conveys the information that the path between a
      source and a destination traverses the ANEs in the same order as
      they appear in the Path Vector.

NEW

Path Vector: A Path Vector, or an ANE Path Vector, is a JSON array
      of ANE Names.  This extension (i.e., ALTO path vector extension)
generalizes
      BGP path vector, where a standard BGP path vector specifies the
sequence of
      autonomous systems from a source to a destination. In this extension,
the path
      vector specifies the sequence of general ANEs computed according to a
user
      request.

.- Section 4.2 – it refers to recent use cases, but it is not relevant how
> recent are the use cases (in fact, for this, see my next comment). So I
> would suggest to remove any reference to recent either in the title or the
> text. Simply refer to use cases.
>

Very good point. We have removed the word "recent" in the title and the
text.



> .- Section 4.2 – there is a reference to an expired I-D which last from
> 2013 (so pretty old). I would suggest to remove such a reference since
> somehow the potential use cases it refers should be present here.
>

Sounds good. Yes. Removed.


> .- Section 5.1.3, 2nd paragraph – “… and the response must return and
> only return the selected properties …” – two comments here: (1) must should
> be MUST in this context?; (2) “… and only return …” – probably redundant,
> better either remove or rephrase as “MUST/must only return”.
>

Good point.

OLD
   "... and the
   response must return and only return the selected properties for the
   ANEs in the response."


NEW
  "... and the
   response MUST include and only include the selected properties specified
in the filter. "

.- Figure 4 – the figure shows two response messages, but some questions
> arise in this respect: (1) what happens if second response is not
> received?; (2) what happens if only the second response is received? Is it
> silently discarded?; (3) is there some expected timer for accounting
> time-out in the responses? It is mentioned in bullet 2 that there could be
> some processing among messages, so it can be assumed that some maximum
> delay could happen between both responses.
>

Good point.

OLD
  Specifically, the
   Path Vector extension requires the ALTO client to include the source
   and destination pairs and the requested ANE properties in a single
   request, and encapsulates both Path Vectors and properties associated
   with the ANEs in a single response, as shown in Figure 4.

NEW

  Specifically, the
   Path Vector extension requires that (1) the ALTO client include the
source
   and destination pairs and the requested ANE properties in a single
   request; (2) the ALTO server MUST return a single response with the Path
Vectors followed by the
   properties associated with the ANEs in the Path Vectors, as shown in
Figure 4.

In addition, in 5.3.3, we add the specification on the essential
completeness issue:

OLD
5.3.3. Order of Part Message

NEW
5.3.3. Order and Completeness of Part Message

We add a sentence at the end of 5.3.3

   The ALTO server MUST always send the complete response including both
parts. The client should check the completeness of response and
implementing a timeout mechanism to avoid hanging issues.


.- Section 6.2.4, last paragraph - Hard to understand, not clear. Please,
> rephrase/review.
>

OLD
   Specifically, the defining resource of ephemeral ANEs is the Property
   Map part of the multipart response.  The defining resource of
   persistent ANEs is the Property Map on which standalone queries for
   properties of persistent ANEs are made.

NEW
   Note that there are two types of ANEs (see Section 5.1.2): ephemeral
ANEs and
   persistent ANEs. For ephemeral ANEs, the defining resource is the
Property
   Map part of the multipart response; the defining resource of
   persistent ANEs is the Property Map on which standalone queries for
   properties of persistent ANEs are made.

.- Section 6.4.2, Intended semantics text – it is not clear the association
> of persistent to ephemeral. Why is this? What is the purpose?
>
.- Section 6.4.2, last paragraph – The value of ephemeral is provided, but
> what would be the value of persistent one?
>

It looks that we need a bit more update. We will finalize the update
shortly.


> .- Section 9.3, 1st and past paragraph – they seem inconsistent since in
> one hand the first claims incompatibility while the second claims
> compatibility. Please, review them.
>

As SSE is finalized now, we will update this part shortly.


> .- Section 9.4 – When used with the calendar extension, should the ANE be
> always persistent? I mean, same ANE for all the time views, otherwise could
> not properly work. Please, clarify.
>

It should. We will update.


>
>
> /* Editorial comments */
>
> .- Section I Introduction, pag. 5, penultimate paragraph – “… Path Vector
> response involve two ALTO …” -> “… Path Vector response involves two ALTO
> …”
>

Good catch. Fixed.


> .- Section I Introduction, pag. 5, last paragraph – “… the rest of the
> document are organized …” -> “… the rest of the document is organized …”
>

Good catch. Fixed.


> .- Section III Terminology stands that the document extends the
> terminology used in RFC 7285 and in Unified Properties draft. This implies
> some precedence in the edition of the documents as RFCs, if they finally
> progress to that stage. So I would recommend to add a note for RFC Editor
> mention that precedence (note to be remove once the document becomes a RFC).
>

Good idea. Unified, which is newer, should have precedence.


> .- Section 5.1 – the text (2nd paragraph) auto-refers to section 5.1.
> Redundant, better to remove.
>

Fixed.


> .- Section 5.2 – 1st paragraph – correct -> correctly
>

Fixed.


> .- Section 5.3, last sentence before Figure 4 – “… the ANEs in a single
> response …” -> “… the ANEs in an additional response …”
>

Fixed.


> .- Section 6.6 – The second paragraph starts with NOTE; probably better to
> rephrase writing it as a normal paragraph.
>

Chaned to "Note that ..."


> .- Section 9.2, last sentence – “compatible” -> “compatibility”
>
>
>

Good catch. Fixed.

Thank you so so much!!

Richard


> Best regards
>
>
>
> Luis
>
>
>
> __________________________________
>
> Luis M. Contreras
>
>
>
> Technology and Planning
>
> Transport, IP and Interconnection Networks
>
> Telefónica I+D / Global CTIO unit / Telefónica
>
>
>
> Distrito Telefónica, Edificio Sur 3, Planta 3
>
> 28050 Madrid
>
> España / Spain
>
>
>
> Skype (Lync): +34 91 312 9084
>
> Mobile: +34 680 947 650
>
> luismiguel.contrerasmurillo@telefonica.com
>
>
>
>
>
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-- 
-- 
 =====================================
| Y. Richard Yang <yry@cs.yale.edu>   |
| Professor of Computer Science       |
| http://www.cs.yale.edu/~yry/        |
 =====================================