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

[Lou Berger <[e-mail]>]

They also share control plane / "connection" fate.

Lou

On 10/14/2013 10:34 AM, Alexander Vainshtein wrote:
> 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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>>
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