Re: [mpls] RtgDir review: draft-ietf-mpls-tp-rosetta-stone-12.txt

[Alexander Vainshtein <[e-mail]>]

John,
Not sure I fully understood your message. 

My comments have been about applicability of the term "fate-sharing" to the two directions of a co-routed bi-directional LSP.
It is of course true that each direction of an associated bi-directional LSP can fail independently of the other one, but, presumably, nobody has expected anything else in this case.

Regards,
     Sasha


> -----Original Message-----
> From: John E Drake [mailto:[e-mail]]
> Sent: Monday, October 14, 2013 4:42 PM
> To: Alexander Vainshtein; Bhatia, Manav (Manav)
> Cc: [e-mail]; [e-mail]; draft-ietf-mpls-tp-rosetta-
> [e-mail]; [e-mail]
> Subject: RE: RtgDir review: draft-ietf-mpls-tp-rosetta-stone-12.txt
> 
> Sasha,
> 
> I think your comments apply equally to bidirectional LSPs.
> 
> Yours Irrespectively,
> 
> John
> 
> > -----Original Message-----
> > From: [e-mail] [mailto:[e-mail]] On Behalf
> Of
> > Alexander Vainshtein
> > Sent: Sunday, October 13, 2013 9:16 AM
> > To: Bhatia, Manav (Manav)
> > Cc: [e-mail]; [e-mail]; draft-ietf-mpls-tp-rosetta-
> > [e-mail]; [e-mail]
> > Subject: Re: [RTG-DIR] RtgDir review: draft-ietf-mpls-tp-rosetta-stone-12.txt
> >
> > Manav and all,
> > Regarding one of the nits you've identified:
> > "it would be useful to mention that an important property of co-routed
> > bidirectional path is that the forward and backward directions share fate."
> >
> > IMHO and FWIW this is not correct. To the best of my understanding the two
> > directions of an MPLS-TP co-routed bi-directional path share lifespan (i.e.,they
> > are set up and torn down in a single management or control plane operation).
> > But they do not share fate, as can be seen from the following examples:
> >
> > 1. A unidirectiona fiber cut in one of the links used by a co-routed bi-
> directional
> > trail will result in traffic failur in the affected direction but not necessarily in
> the
> > reverse one
> >
> > 2. Consider the case when one of entries the ILM in one of the transit LSRs is
> > corruped. This will result in incorrect failure of a single label, but the rest of
> the
> > labels would be handled correctly. Since co-routed bi-directional trails do not
> > require using the same label in both directions of a trail, the fate sharing
> would
> > be broken.
> > (Actually, in such a way it could be easily broken even if the same label is
> used
> > on each segment of the LSP in both directions...)
> >
> > My 2c,
> >      Sasha
> >
> >
> >
> > ________________________________________
> > From: [e-mail] [[e-mail]] on behalf of Bhatia,
> > Manav (Manav) [[e-mail]]
> > Sent: Sunday, October 13, 2013 5:55 PM
> > To: [e-mail]
> > Cc: [e-mail]; [e-mail];
> > [e-mail]
> > Subject: [RTG-DIR] RtgDir review: draft-ietf-mpls-tp-rosetta-stone-12.txt
> >
> > Hello,
> >
> > I have been selected as the Routing Directorate reviewer for this draft. The
> > Routing Directorate seeks to review all routing or routing-related drafts as
> > they pass through IETF last call and IESG review, and sometimes on special
> > request. The purpose of the review is to provide assistance to the Routing
> > ADs. For more information about the Routing Directorate, please
> > seehttp://www.ietf.org/iesg/directorate/routing.html
> >
> > Although these comments are primarily for the use of the Routing ADs, it
> > would be helpful if you could consider them along with any other IETF Last
> Call
> > comments that you receive, and strive to resolve them through discussion or
> > by updating the draft.
> >
> > Document: draft-ietf-mpls-tp-rosetta-stone-12.txt
> > Reviewer: Manav Bhatia
> > Review Date: October 13th, 2013
> > IETF LC End Date: October 16, 2013
> > Intended Status: Informational
> >
> > Summary:  This document is basically ready for publication, but has nits that
> > should be considered prior to publication.
> >
> > Comments: This document is built on top of terms already defined in different
> > RFCs and ITU-T documents. The terms and definitions have already been
> > reviewed so there is a trifle little that needs to be done there. Overall, the
> > document looks good and ready for publication. Some of my comments can be
> >
> > Nits:
> >
> > o) Please expand PW in either the Abstract or Sec 3.5
> >
> > o) When explaining Control Plane (3.6) should we mention that it is possible
> to
> > operate an MPLS-TP network without using a Control Plane?
> >
> > o) In 3.7, it would be useful to mention that an important property of co-
> routed
> > bidirectional path is that the forward and backward directions share fate.
> > Similarly, in 3.1, we should mention that the forward and backward directions
> > don't share fate.
> >
> > o) 3.12 in the current text doesn't look very helpful. Can it be rephrased it to
> > something like, "The equipment management function (EMF) provides the
> > means through which an element management system (EMS) and other
> > managing entities manage the network element function (NEF)."
> >
> > o) 3.13 talks about Fault cause without explaining what a fault cause is. It
> took
> > me some time to understand what was meant by "fault cause". Can the
> > authors of the draft rephrase 3.13 in their own language to explain what they
> > mean by a Failure. The current definition in the draft has been picked up as-is
> > from ITU-T G.806
> >
> > o) 3.14 talks about "inability of a function to perform a required action". Since
> > this RFC-to-be is in the IETF domain, can this be rephrased to use a term like
> > router/switch instead of a more esoteric "function". This is a general
> comment
> > and applies to most of the definitions that have been copied from the ITU-T
> > documents.
> >
> > o) The last paragraph of 3.17 says the following:
> >
> > "OAM packets are subject to the same forwarding treatment as the data
> > traffic, but they are distinct from the data traffic."
> >
> > In what sense are the OAM packets distinct from the data traffic?
> >
> > o) Please include "T-PE" and "S-PE" in Sec 1.2. These have not been expanded
> > in the document.
> >
> > o) Sec 3.19 uses TCM without expanding it first.
> >
> > o) In Sec 3.23, s/Tandem Connections/Tandem Connection
> >
> > o) In 3.28.3, can the following text be added:
> >
> > An LSP segment comprises one or more continuous hops on the path of the
> > LSP.  [RFC5654] defines two terms.  A "segment" is a single hop along the
> path
> > of an LSP, while a "concatenated segment" is more than one hop along the
> > path of an LSP.
> >
> > o) In 3.31, Isn't Operations Support Systems (OSS) a more common term than
> > Operations Systems (OS)?
> >
> > Cheers, Manav
> >
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