Re: [PWE3] Fwd: I-D Action: draft-shawam-pwe3-ms-pw-protection-01.txt

"Andrew G. Malis" <agmalis@gmail.com> Mon, 29 September 2014 11:46 UTC

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From: "Andrew G. Malis" <agmalis@gmail.com>
Date: Mon, 29 Sep 2014 07:46:21 -0400
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To: Alexander Vainshtein <Alexander.Vainshtein@ecitele.com>
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Subject: Re: [PWE3] Fwd: I-D Action: draft-shawam-pwe3-ms-pw-protection-01.txt
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Sasha,

Thanks for your comments. In order:

1. No, the intended scope of this draft is Section 3.2.3 of RFC 6718 and
Section A.5 of RFC 6870, which describe a single-homed CE. They both use
the same network model diagram. I hadn't thought it was necessary to
replicate that diagram a third time, but I certainly can and will in the
next revision.

2. This is actually discussed in those two sections. Basically, the entire
primary PW is protected against failure by switching to the secondary PW if
the primary fails for any reason. In the case of a MS-PW where the
individual segments are each protected via tunnel protection, the likely
cause of primary PW failure would be S-PE failure.

3. You're actually thinking of the -00 revision of this draft. That is the
approach that was presented at the Toronto PWE3 meeting, and the consensus
of the discussion was that the approach in this revision should be used
instead.

Cheers,
Andy

On Sun, Sep 28, 2014 at 1:03 AM, Alexander Vainshtein <
Alexander.Vainshtein@ecitele.com> wrote:

>  Andy,
>
> I've read the draft and re-read RFC 6780, and I have a couple of
> questions/comments that, from my point of view, should be clarified in the
> next revision of the draft.
>
>    1. RFC 6780 and RFC 6718 describe multiple use cases for PW
>    redundancy, including use cases with dual-homed CEs, use cases for VPLS
>    etc. The draft refers to specific sections in these RFCs that deal with the *use
>    case of two single-homed CEs, so I guess that this is the intended scope of
>    the draft*. Is this assumption correct? If yes, I would suggest
>    stating this explicitly and even including the corresponding reference
>    network model diagram in the draft. This would not unduly expand the
>    document while making it much more readable IMO.  (And maybe you should
>    mention draft-cheng-pwe3-mpls-tp-dual-homing-protection a dealing with the
>    dual-homing use cases?)
>    2. RFC 6870 does not explain how S-PE failure is detected. I assume
>    that one of the possible ways to do that could be by treating failure of
>    the targeted/indirect LDP session between this S-PE and its adjacent PEs as
>    S-PE failure. This is clearly not relevant in the case of statically set up
>    MS-PWs. I would suggest adding a few words regarding possible methods for
>    detecting S-PE failure. (As an absolute minimum, you could state that this
>    is out of scope of the document...)
>    3. To the best of my recollection somebody has once posted a
>    draft that suggested treating static MS-PWs as MPLS-TP co-routed
>    bi-directional LSPs (which is true)and applying LSP Linear Protection for
>    end-to-end protection of MS-PWs. This draft has long expired, but maybe the
>    idea should be mentioned as a possible alternative approach?
>
> With these points in mind, I think that the draft is mature enough to be
> adopted as a WG document (even if you did not ask for that:-).
>
>
>
> Regards,
>
> Sasha
>  ------------------------------
>  *From:* pwe3 <pwe3-bounces@ietf.org> on behalf of Andrew G. Malis <
> agmalis@gmail.com>
> *Sent:* Saturday, September 27, 2014 6:02 PM
> *To:* pwe3@ietf.org
> *Subject:* [PWE3] Fwd: I-D Action:
> draft-shawam-pwe3-ms-pw-protection-01.txt
>
>   PWE3ers,
>
>  Revision -00 of this draft was presented at the Toronto IETF and we
> received good feedback from the WG. We've updated the draft to incorporate
> the received comments. The draft plugs an important hole in resilience for
> static MS-PWs. Please review and comment to the list, it's a very quick
> read.
>
>  Thanks,
> Andy
>
> ---------- Forwarded message ----------
> From: <internet-drafts@ietf.org>
> Date: Fri, Sep 26, 2014 at 6:05 PM
> Subject: I-D Action: draft-shawam-pwe3-ms-pw-protection-01.txt
> To: i-d-announce@ietf.org
>
> A New Internet-Draft is available from the on-line Internet-Drafts
> directories.
>
>         Title           : S-PE Outage Protection for Static Multi-Segment
> Pseudowires
>         Authors         : Andrew G. Malis
>                           Loa Andersson
>                           Huub van Helvoort
>                           Jongyoon Shin
>                           Lei Wang
>                           Alessandro D'Alessandro
>         Filename        : draft-shawam-pwe3-ms-pw-protection-01.txt
>         Pages           : 5
>         Date            : 2014-09-26
>
> Abstract:
>    In MPLS and MPLS-TP environments, statically provisioned Single-
>    Segment Pseudowires (SS-PWs) are protected against tunnel failure via
>    MPLS-level and MPLS-TP-level tunnel protection.  With statically
>    provisioned Multi-Segment Pseudowires (MS-PWs), each segment of the
>    MS-PW is likewise protected from tunnel failures via MPLS-level and
>    MPLS-TP-level tunnel protection.  However, static MS-PWs are not
>    protected end-to-end against failure of one of the switching PEs
>    (S-PEs) along the path of the MS-PW.  This document describes how to
>    achieve this protection by updating the existing procedures in RFC
>    6870.
>
>
> The IETF datatracker status page for this draft is:
> https://datatracker.ietf.org/doc/draft-shawam-pwe3-ms-pw-protection/
>
> There's also a htmlized version available at:
> http://tools.ietf.org/html/draft-shawam-pwe3-ms-pw-protection-01
>
> A diff from the previous version is available at:
> http://www.ietf.org/rfcdiff?url2=draft-shawam-pwe3-ms-pw-protection-01
>
>
> Please note that it may take a couple of minutes from the time of
> submission
> until the htmlized version and diff are available at tools.ietf.org.
>
> Internet-Drafts are also available by anonymous FTP at:
> ftp://ftp.ietf.org/internet-drafts/
>
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