Re: [mpls] [spring] to progress draft-cheng-spring-mpls-path-segment

Greg Mirsky <gregimirsky@gmail.com> Sat, 16 February 2019 21:24 UTC

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From: Greg Mirsky <gregimirsky@gmail.com>
Date: Sat, 16 Feb 2019 13:24:09 -0800
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To: Weiqiang Cheng <chengweiqiang@chinamobile.com>
Cc: Alexander Vainshtein <Alexander.Vainshtein@ecitele.com>, spring <spring@ietf.org>, Stewart Bryant <stewart.bryant@gmail.com>, draft-cheng-spring-mpls-path-segment@ietf.org, mpls@ietf.org, Loa Andersson <loa@pi.nu>
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Subject: Re: [mpls] [spring] to progress draft-cheng-spring-mpls-path-segment
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Hi Weiqiang Cheng,
thank you for your expedient response to my questions. The document states
that one of the use cases for the Path segment is to be used as a
performance, packet loss and/or delay, measurement session identifier. I
think that RFC 6374 is the most suitable for PM OAM in SR-MPLS environment.
Of course, the type of the encapsulated message can be identified using the
destination UDP port number with IP/UDP encapsulation. But another option
is to use G-ACh encapsulation. That would require the use of GAL. And that
is how I've arrived at my original question (I should have explained it
better, my apologies):

How the Path segment and GAL are placed relative to each other in the
SR-MPLS label stack?

Regards,
Greg

On Fri, Feb 15, 2019 at 4:40 PM Weiqiang Cheng <
chengweiqiang@chinamobile.com> wrote:

> Hi Greg,
>
> Thanks a lot for your comments.
>
> My comments are in-line.
>
>
>
> B.R.
>
> Weiqiang Cheng
>
>
>
> *发件人:* Greg Mirsky [mailto:gregimirsky@gmail.com]
> *发送时间:* 2019年2月15日 3:37
> *收件人:* Alexander Vainshtein
> *抄送:* spring@ietf.org; Stewart Bryant;
> draft-cheng-spring-mpls-path-segment@ietf.org; mpls@ietf.org; Loa
> Andersson
> *主题:* Re: [spring] to progress draft-cheng-spring-mpls-path-segment
>
>
>
> Dear All,
>
> I concur with all what has been said in support of the adoption of this
> draft by SPRING WG. The document is well-written, addresses the real
> problem in SR-MPLS, and the proposed solution is technically viable.
>
> My comments and questions are entirely for further discussion:
>
>    - would the draft be expanded to demonstrate how "the Path Segment may
>    be used to identify an SR-MPLS Policy, its Candidate-Path (CP) or a SID
>    List (SL)"?
>
> [Weiqiang] Yes, It is necessary and we will add some text to demonstrate
> this in the future version.
>
>    - as many use cases for the Path Segment are related to OAM
>    operations, it would be helpful to expand on the use of GAL and the Path
>    Segment.
>
>        [Weiqiang] It is always helpful to have more use cases. However,
> The GAL is used today in MPLS-TP LSPs to flag the G-Ach and is used for OAM
> packets only while the Path segment is used for data packets for the each
> traffic flow. It is a little bit different.
>
> Regards,
>
> Greg
>
>
>
> On Thu, Feb 14, 2019 at 1:12 AM Alexander Vainshtein <
> Alexander.Vainshtein@ecitele.com> wrote:
>
> +1.
>
>
>
> I have been following this draft from its -00 revision. The current
> revision has resolved most of the issues I (and others) have been raised
> (e.g., elimination of excessive options).
>
>
>
> From my POV, in its current state the draft meets two basic requirements
> for the WG adoption:
>
> 1.       It addresses a real and relevant problem, namely the MPLS Flow
> Identification problem discussed in general in RFC 8372
> <https://tools.ietf.org/html/rfc8372> and scoped to SR-MPLS LSPs in this
> draft. Specifics of SR-MPLS include the need to provide end-to-end liveness
> check that is one of the requirements explicitly specified in Section 2 of RFC
> 8355 <https://tools.ietf.org/html/rfc8355>.
>
> 2.       It provides a reasonable (from my POV) approach to  solution of
> this problem.
>
>
>
> I also concur with Stewart’s comment about strong similarity between the
> approach taken in this draft for SR-MPLS and generic work in progress on
> synonymous flow labels
> <https://tools.ietf.org/html/draft-ietf-mpls-sfl-framework-04> that has
> been already adopted as a MPLS WG item.  To me this is yet another
> indication that the draft should be adopted.
>
>
>
> My 2c,
>
> Sasha
>
>
>
> Office: +972-39266302
>
> Cell:      +972-549266302
>
> Email:   Alexander.Vainshtein@ecitele.com
>
>
>
> -----Original Message-----
> From: spring <spring-bounces@ietf.org> On Behalf Of Stewart Bryant
> Sent: Wednesday, February 13, 2019 12:48 PM
> To: Loa Andersson <loa@pi..nu <loa@pi.nu>>u>>; spring@ietf.org;
> draft-cheng-spring-mpls-path-segment@ietf.org
> Subject: Re: [spring] to progress draft-cheng-spring-mpls-path-segment
>
>
>
> I have just read the draft and agree that it should be adopted by the WG.
> It solves an important problem in instrumenting and protecting an SR path.
>
>
>
> It should be noted that we needed to do something very similar in
> mainstream MPLS via the synonymous label work which is already adopted.
>
> However SL did not address the SR case. We therefore need this path label
> work to be progressed.
>
>
>
> - Stewart
>
>
>
> On 10/02/2019 08:11, Loa Andersson wrote:
>
> > Working Group,
>
> >
>
> > I have reviewed draft-cheng-spring-mpls-path-segment and as far as I
>
> > can see, it is ready for wg adoption.
>
> >
>
> > There were some comments in Bangkok, but due to the many collisions
>
> > between working groups at that meeting I couldn't attend the SPRING
>
> > f2f.
>
> >
>
> > The minutes are not clear, but as far as I understand, there is
>
> > nothing that can't be resolved in the wg process.
>
> >
>
> > /Loa
>
>
>
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