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

"Andrew G. Malis" <agmalis@gmail.com> Mon, 29 September 2014 22:04 UTC

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From: "Andrew G. Malis" <agmalis@gmail.com>
Date: Mon, 29 Sep 2014 18:03:17 -0400
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To: Alexander Vainshtein <Alexander.Vainshtein@ecitele.com>
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Cc: "pwe3@ietf.org" <pwe3@ietf.org>, "huubatwork@gmail.com" <huubatwork@gmail.com>
Subject: Re: [PWE3] Fwd: I-D Action: draft-shawam-pwe3-ms-pw-protection-01.txt
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Sasha,

Thanks!

All, I'm planning another update prior to the pre-Hawaii deadline to
incorporate Sasha's comments and any others that come in. Please read and
comment.

Cheers,
Andy

On Mon, Sep 29, 2014 at 10:15 AM, Alexander Vainshtein <
Alexander.Vainshtein@ecitele.com>; wrote:

>  Andy,
>
> I am OK with this.
>
>
>
> Regards,
>
>        Sasha
>
> Email: Alexander.Vainshtein@ecitele.com
>
> Mobile: 054-9266302
>
>
>
> *From:* Andrew G. Malis [mailto:agmalis@gmail.com]
> *Sent:* Monday, September 29, 2014 5:14 PM
> *To:* Alexander Vainshtein
> *Cc:* huubatwork@gmail.com; pwe3@ietf.org
>
> *Subject:* Re: [PWE3] Fwd: I-D Action:
> draft-shawam-pwe3-ms-pw-protection-01.txt
>
>
>
> Sasha,
>
>
>
> Typically, solution drafts don't include alternative rejected approaches,
> usually it's a framework or architecture draft that discusses the universe
> of possible approaches.
>
>
>
> The IPLS draft is being published because the concepts in the original
> work have been adopted by newer work, thus making it interesting
> historically.
>
>
>
> Cheers,
>
> Andy
>
>
>
> On Mon, Sep 29, 2014 at 9:44 AM, Alexander Vainshtein <
> Alexander.Vainshtein@ecitele.com>; wrote:
>
> Huub,
>
> To the best of my understanding RFC 6478 is all about Static PW Status
> messages.
> So I am not sure what you mean when you say "use it also for PW".
>
> The draft actually proposes to use the PW redundancy mechanisms defined in
> RFC 6718 and RFC 6870 for static MS-PWs using static PW Status messages
> (defined in RFC 6478) in order to carry the "forwarding preference" and
> "request switchover" bits needed for  PW redundancy.
>
> As for an alternative approach - I believe I have been misunderstood,
> probably did not present my position clearly.
> I did not mean that linear protection should be presented as an optional
> alternative solution, just that it should be mentioned as an approach that
> has been considered and rejected.
>
> To the best of my recollection, the L2VPN WG is now advancing the IPLS
> draft to become a Historic RFC for the same purpose - to record an idea
> that has been considered and rejected...
> (Not sure if we can consider this as a precedent - the IPLS draft has been
> in limbo for more than 10 years IMO. Does age count as a special merit?:-)
>
> Regards,
>        Sasha
> Email: Alexander.Vainshtein@ecitele.com
> Mobile: 054-9266302
>
>   > -----Original Message-----
> > From: pwe3 [mailto:pwe3-bounces@ietf.org] On Behalf Of Huub van
> > Helvoort
> > Sent: Monday, September 29, 2014 4:34 PM
> > To: pwe3@ietf.org
> > Subject: Re: [PWE3] Fwd: I-D Action: draft-shawam-pwe3-ms-pw-protection-
> > 01.txt
> >
> > Hello,
> >
> > I agree with the assessment from Andy.
> > Use the mechanism in RFC6478 also for PW.
> > A single approach is much less complex to provision.
> >
> > Suppose there is a second approach, do _we_ have to search for it?
> > Then it has to determined which is preferred/better to use as default,
> > Maybe there is even a third approach...
> >
> > Best regards, Huub.
> >
> > > The mechanism for static PW failure handling is in RFC 6478, which is
> > > also referenced in the draft.
> > >
> > > The primary purpose for an RFC is interoperability. If the draft
> > > contains more than one approach, then one of those approaches has to
> > > be mandatory to implement and use, and the other optional, otherwise
> > > you can't assure interoperability. In which case, does it make sense
> > > to include more than one approach and make one optional to implement?
> > > And of course, if you implement both, then the primary approach has to
> > > be the default one used. Then you'll also require either consistent
> > > provisioning to make sure that the two ends agree on the approach
> > > used, or a negotiation mechanism. It seems like you're adding a lot of
> > > work to document more than one approach.
> > >
> > > Cheers,
> > > Andy
> > >
> > >
> > > On Mon, Sep 29, 2014 at 8:03 AM, Alexander Vainshtein
> > > <Alexander.Vainshtein@ecitele.com
> > > <mailto:Alexander.Vainshtein@ecitele.com>> wrote:
> > >
> > >     Andy,____
> > >
> > >     Lots of thanks for a prompt and detailed response. Please see more
> > >     */inline below/*.____
> > >
> > >     __ __
> > >
> > >     Regards,____
> > >
> > >             Sasha ____
> > >
> > >     Email: Alexander.Vainshtein@ecitele.com
> > >     <mailto:Alexander.Vainshtein@ecitele.com>____
> > >
> > >     Mobile: 054-9266302____
> > >
> > >     __ __
> > >
> > >     *From:*Andrew G. Malis [mailto:agmalis@gmail.com
> > >     <mailto:agmalis@gmail.com>]
> > >     *Sent:* Monday, September 29, 2014 2:46 PM
> > >     *To:* Alexander Vainshtein
> > >     *Cc:* pwe3@ietf.org <mailto:pwe3@ietf.org>
> > >     *Subject:* Re: [PWE3] Fwd: I-D Action:
> > >     draft-shawam-pwe3-ms-pw-protection-01.txt____
> > >
> > >     __ __
> > >
> > >     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.*/[[Sasha]] Great! /*____
> > >
> > >     __ __
> > >
> > >     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.*/[[Sasha]] I have looked up these sections again, and they
> > >     say “If active/primary PW fails…”. They also mention  that
> typically
> > >     the reason for PW failure (end-to-end) is S-PE failure. But no
> > >     specific method for detecting the failure of the primary/active PW
> > >     is mentioned. Maybe this should be expanded a bit in the draft with
> > >     emphasis on methods that are specific to MPLS-TP and statically
> > >     configured MS-PWs? /*____
> > >
> > >     __ __
> > >
> > >     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.*/[[Sasha]] Could be my mistake.
> And
> > >     even if the approach has been changed from -00 to -01, I think that
> > >     mentioning an alternative approach would be nice IMO. /*____
> > >
> > >     __ __
> > >
> > >     Cheers,____
> > >
> > >     Andy____
> > >
> > >     __ __
> > >
> > >     On Sun, Sep 28, 2014 at 1:03 AM, Alexander Vainshtein
> > >     <Alexander.Vainshtein@ecitele.com
> > >     <mailto: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 <mailto:pwe3-
> > bounces@ietf.org>>;
> > >     on behalf of Andrew G. Malis <agmalis@gmail.com
> > >     <mailto:agmalis@gmail.com>>
> > >     *Sent:* Saturday, September 27, 2014 6:02 PM
> > >     *To:* pwe3@ietf.org <mailto: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 <mailto: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 <mailto: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
> > >     <http://tools.ietf.org>;.
> > >
> > >     Internet-Drafts are also available by anonymous FTP at:
> > >     ftp://ftp.ietf.org/internet-drafts/
> >
> >
> > --
> > **********************************************************
> > *******
> >                请记住,你是独一无二的,就像其他每一个人一样
> >
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