Re: AD review of draft-ietf-bfd-multipoint-14

Greg Mirsky <gregimirsky@gmail.com> Tue, 17 April 2018 18:40 UTC

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From: Greg Mirsky <gregimirsky@gmail.com>
Date: Tue, 17 Apr 2018 11:40:16 -0700
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Subject: Re: AD review of draft-ietf-bfd-multipoint-14
To: Martin Vigoureux <martin.vigoureux@nokia.com>
Cc: draft-ietf-bfd-multipoint@ietf.org, "Reshad Rahman (rrahman)" <rrahman@cisco.com>, bfd-chairs@ietf.org, rtg-bfd@ietf.org
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Hi Martin,
I have not ignored that comment but missed to ack its acceptance. Two other
outstanding questions:

   - the text, that I've misinterpreted earlier, is in the Overview section:

        Although this document describes a single head and a set of tails
>         spanned by a single multipoint path, the protocol is capable of
>         supporting (and discriminating between) more than one multipoint
>     path
>         at both heads and tails.
>     There is no text to describe how one could achieve that. Wouldn't it
>     be worth adding some?
>
> GIM>> The question of applicability of this specification to mp2mp
> scenario came up at BIER WG meeting in London. Perhaps we can say the these
> questions are ouside the scope of this document and discuss whether there
> are interested to work on mp2mp case as a separete document?
>
I don't read this part of the document as talking about mp2mp but rather as
talking about multiple p2mp trees.

Sections 4.7 and 4.13.2 provides details on demultiplexing BFD control
packets at a MultipointTail. Would the reference to these sections be
sufficient?


   - yes, moved the reference to Point-to-Point session to section 4.4.1

Attached please find the diff between -14 and the working version of the
draft. Please let me know if the changes address your comments. Will upload
the new version promptly.

Regards,
Greg

On Tue, Apr 17, 2018 at 9:49 AM, Martin Vigoureux <
martin.vigoureux@nokia.com> wrote:

> Greg,
>
> thanks. please see in-line.
>
> once I see the update published I will request IETF LC.
>
> -m
>
> Le 2018-04-17 à 18:34, Greg Mirsky a écrit :
>
>> Hi Martin,
>> thank you for your thorough review, thoughtful comments and kind words.
>> Please find my answers to your questions in-line and tagged GIM>>.
>>
>> Regards,
>> Greg
>>
>> On Tue, Apr 17, 2018 at 8:06 AM, Martin Vigoureux <
>> martin.vigoureux@nokia.com <mailto:martin.vigoureux@nokia.com>> wrote:
>>
>>     [resend, wrong bfd wg address in first attempt ...]
>>
>>     Authors, WG,
>>
>>     thank you for this document. It is clear and well written.
>>     I didn't find any technical comment to make so I've been nit picking
>> :-)
>>     Please find those comments below.
>>
>>     regards,
>>     martin
>>
>>     ---
>>     Please check and address the nits:
>>     https://tools.ietf.org/idnits?url=https://tools.ietf.org/id/
>> draft-ietf-bfd-multipoint-14.txt
>>     <https://tools.ietf.org/idnits?url=https://tools.ietf.org/
>> id/draft-ietf-bfd-multipoint-14.txt>
>>
>>     On that aspect, does this document really update 7880 as the header
>>     says? The Introduction only refers to 5880 and it is not clear in
>>     the body of the Document what effectively impacts 7880. The only
>>     thing I saw is the addition of new session types but that does not
>>     require an update in my opinion. Could you clarify?
>>     GIM>> Yes, you'correct, the only connection to RFC 7880 are the new
>>     values of bfd.sessionType. The proposal to list RFC 7880 as updated
>>     by this specification was inteded to address Errata to RFC 7880
>>     <https://www.rfc-editor.org/errata_search.php?rfc=7880>.
>>
> I am not sure how this document relates to or addresses the errata. So I
> still think it does not update 7880.
>
>
>>         i.e. existence of a path between the sender and the receiver.
>>     do you mean "forwarding path"?
>>     GIM>> Yes. Updated to
>>
>>     i.e. existence of a forwarding path between the sender and the
>> receiver
>>
> thx
>
>>
>>     Section 2. and Section 3. seem a bit redundant. They both state the
>>     same thing but from a different angle. Not critical.
>>
>>
>>         Although this document describes a single head and a set of tails
>>         spanned by a single multipoint path, the protocol is capable of
>>         supporting (and discriminating between) more than one multipoint
>>     path
>>         at both heads and tails.
>>     There is no text to describe how one could achieve that. Wouldn't it
>>     be worth adding some?
>>
>> GIM>> The question of applicability of this specification to mp2mp
>> scenario came up at BIER WG meeting in London. Perhaps we can say the these
>> questions are ouside the scope of this document and discuss whether there
>> are interested to work on mp2mp case as a separete document?
>>
> I don't read this part of the document as talking about mp2mp but rather
> as talking about multiple p2mp trees.
>
>>
>>
>>
>>         Point-to-point sessions, as described in [RFC5880], are of type
>>         PointToPoint.
>>     Does this really fit in Section 4.2 which looks to be about the
>>     mpBFD session model.
>>
>> GIM>> I think that this short reminder is helpful to explain why this
>> document adds value PointToPoint, section 4.4.1, to the defined in RFC 7880
>> bfd.sessionType variable.
>>
> Well, I would move the text to 4.4.1 then, but not critical.
>
>>
>>
>>
>>         Sessions of type MultipointHead MUST NOT send BFD control packets
>>         with the State field being set to INIT, and MUST be ignored on
>>         receipt.
>>     English is not my native language but I wonder if this really says
>>     what you want. It seems that "Sessions" is the subject of "MUST be
>>     ignored" while I think it's the packets which are the intended
>>     subject. So I'd write:
>>         and those packets MUST be ignored on receipt.
>>
> You chose to ignore that one or simply missed it?
>
>>
>>
>>         Because there is no three-way handshake in Multipoint BFD, a newly
>>         started head (that does not have any previous state information
>>         available) SHOULD start with bfd.SessionState set to Down and with
>>         bfd.RequiredMinRxInterval set to zero in the MultipointHead
>> session.
>>
>>         To shut down a multipoint session a head MUST administratively set
>>         bfd.SessionState in the MultipointHead session to either Down or
>>         AdminDown and SHOULD set bfd.RequiredMinRxInterval to zero.  The
>>     In both these paragraphs one could read that the head "SHOULD set
>>     bfd.RequiredMinRxInterval to zero" while 4.4.2 says MUST.
>>     Clarification needed?
>>
>> GIM>> Section 4.4.2 mandates initialization of
>> bfd.RequiredMinRxInterval and, I think, applies to the first paragraph
>> you've pointed. Would the following be clear and consistent:
>>     Because there is no three-way handshake in Multipoint BFD, a newly
>>     started head (that does not have any previous state information
>>     available) SHOULD start with bfd.SessionState set to Down and
>>     bfd.RequiredMinRxInterval _MUST be_ set to zero in the MultipointHead
>> session.
>> The second paragraph describes manipulation with the value of
>> bfd.RequiredMinRxInterval which process, as noted in section 4.10, "is
>> outside the scope of this document". That may be reason to use SHOULD and
>> not MUST.
>>
> Yes, i'd live with that. But then you might also want to clarify in 4.4.2.
> :
> OLD:
>          This variable MUST be set to 0 for session type MultipointHead.
> NEW:
>          This variable MUST be initialized to 0 for session type
>          MultipointHead.
>
>
>
>
>>
>>
>>     s/M, P bit/M and P bits/
>>
>> GIM>> Thanks, done.
>>
>>     ---
>>
>>
>>