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

["Bhatia, Manav (Manav)" <[e-mail]>]

Hi Sasha,

RFC 5960 that describes the MPLS-TP data plane says the following:

A point-to-point co-routed bidirectional LSP is a point-to-point
associated bidirectional LSP with the additional constraint that its
two unidirectional component LSPs in each direction follow the same
path (in terms of both nodes and links).  An important property of
co-routed bidirectional LSPs is that their unidirectional component
LSPs share fate.

Am I missing something?

Cheers, Manav
 

> -----Original Message-----
> From: Alexander Vainshtein [mailto:[e-mail]] 
> Sent: Sunday, October 13, 2013 9:46 PM
> To: Bhatia, Manav (Manav)
> Cc: [e-mail]; 
> [e-mail]; 
> [e-mail]; [e-mail]
> Subject: RE: 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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