Re: [mpls] MPLS-RT experts review for draft-gandhi-mpls-rfc6374-sr

Greg Mirsky <gregimirsky@gmail.com> Sat, 13 June 2020 15:38 UTC

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From: Greg Mirsky <gregimirsky@gmail.com>
Date: Sat, 13 Jun 2020 08:38:11 -0700
Message-ID: <CA+RyBmWW3g9dKDxVi2vojCnowsyBdb4yTCgiouO3Fvw08Ngw0w@mail.gmail.com>
To: Huaimo Chen <huaimo.chen@futurewei.com>
Cc: Tarek Saad <tsaad.net@gmail.com>, "mpls@ietf.org" <mpls@ietf.org>, "mpls-chairs@ietf.org" <mpls-chairs@ietf.org>, "draft-gandhi-mpls-rfc6374-sr@ietf.org" <draft-gandhi-mpls-rfc6374-sr@ietf.org>
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Subject: Re: [mpls] MPLS-RT experts review for draft-gandhi-mpls-rfc6374-sr
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Hi Huiamo,
thank you for your expedient and helpful response to my question. I agree
with your characterization of the proposed method for p2mp SR policies. Do
you see such a solution as sufficient and capable to support the necessary
performance monitoring?

Regards,
Greg

On Fri, Jun 12, 2020 at 8:59 PM Huaimo Chen <huaimo.chen@futurewei.com>
wrote:

> Hi Greg,
>
>     In the contexts of the draft-gandhi-mpls-rfc6374-sr and my comments, one
> way means one way  Measurement Mode, out-of-band means out-of-band probe
> reply.
>
> Best Regards,
> Huaimo
> ------------------------------
> *From:* Greg Mirsky <gregimirsky@gmail.com>
> *Sent:* Friday, June 12, 2020 10:06 PM
> *To:* Huaimo Chen <huaimo.chen@futurewei.com>
> *Cc:* Tarek Saad <tsaad.net@gmail.com>om>; mpls@ietf.org <mpls@ietf.org>rg>;
> mpls-chairs@ietf.org <mpls-chairs@ietf.org>rg>;
> draft-gandhi-mpls-rfc6374-sr@ietf.org <
> draft-gandhi-mpls-rfc6374-sr@ietf.org>
> *Subject:* Re: [mpls] MPLS-RT experts review for
> draft-gandhi-mpls-rfc6374-sr
>
> Hi Huaimo,
> thank you for your comments. Though I am not a co-author of the draft, I
> am very interested in the topic. I have a question related to your comments
> and conclusions below:
>
>    - you've noted "It seems that the Performance Measurement for a SR
>    P2MP Path (or policy) is limited to one way and out-of-band. Should the
>    document add some texts talking about these limitations?" If that truly is
>    the case, i.e., the proposed OAM mechanism can only work as out-of-band,
>    what is the value of the measurement results using the synthetic method of
>    measurement? If, as you have noted, a test packet does not follow the
>    monitored data flow, how trustworthy and useful the loss and delay
>    measurement are achieved? I think that I cannot agree with your
>    conclusion that the prosed PM OAM mechanism can only work as out-of-band
>    tool, i.e., support direct measurement statistics by collecting counters.
>    The fact that a test packet, as described in the draft, uses the precisely
>    same policies as a data packet, in my view, ensures that it is in-band and
>    shares the fate with the data flow, which is essential to obtaining useful
>    performance measurements.
>
> I much appreciate your consideration of my question.
>
> Regards,
> Greg
>
> On Mon, Jun 8, 2020 at 8:52 PM Huaimo Chen <huaimo.chen@futurewei.com>
> wrote:
>
> Hi All,
>
>     I have reviewed the document and have the following comments.
>
>     1.  The document is useful and technically sound. It can be considered
> for WG adoption.
>
>     2.  The document seems talking about the Loss Measurement Message
> and Delay Measurement Message. Should it have some texts for Combined
> Loss/Delay Measurement Message?
>
>     3.  There are a couple of IETF drafts about SR P2MP Path.. The
> document just mentions one of them and the Performance Measurement for a SR
> P2MP Path (or policy) is based on this one draft. Should the Performance
> Measurement for a SR P2MP Path (or policy) be general enough for all?
>
>     4.  It seems that the Performance Measurement for a SR P2MP Path (or
> policy) is limited to one way and out-of-band. Should the document add some
> texts talking about these limitations?
>
>     5.  The registry for the newly defined Return Path TLV Type and Block
> Number TLV Type is missing in the document. Is it the "MPLS Loss/Delay
> Measurement TLV Object" registry?
>
>     6.  It seems that a new registry should be defined for the Sub-TLV
> types under the Return Path TLV in the document.
>
>     7.  In section 5.1. and section 6.1., Should "For both SR Links and
> end-to-end measurement for SR-MPLS Policies" be changed to something like
> "For both SR Links and end-to-end SR-MPLS Policies measurements"?
>
>     8.  In section 6.2., should something like a user case be added into
> the sentence "The Block Number TLV is Mandatory when used.."?
>
>
> Best Regards,
> Huaimo
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