[RTG-DIR] RtgDir review: draft-ietf-mpls-smp-requirements-06.txt
Lou Berger <lberger@labn.net> Sat, 21 June 2014 16:00 UTC
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Date: Sat, 21 Jun 2014 11:59:41 -0400
From: Lou Berger <lberger@labn.net>
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Cc: rtg-dir@ietf.org, draft-ietf-mpls-smp-requirements.all@tools.ietf.org, mpls@ietf.org
Subject: [RTG-DIR] RtgDir review: draft-ietf-mpls-smp-requirements-06.txt
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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 see http://trac.tools.ietf.org/area/rtg/trac/wiki/RtgDir 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-smp-requirements-06.txt Reviewer: Lou Berger Review Date: June 21 2014 IETF LC End Date: 2014-06-23 Intended Status: Informational Summary: I have some minor concerns about this document that I think should (must, actually) be resolved before publication. Comments: I think the document is well written and, other than a couple of terminology related issues, easily understood. The document does have a number of terminology and technical issues which should be readily resolved prior to publication. Major Issues: Major issues are the type of concerns that will result in the document being blocked until they are resolved. The Routing ADs will become involved. Please include all of the major issues you have found. Give as much context information as possible (e.g., section numbers, paragraph counts). If you find no major issues, please write: "No major issues found." - No major issues found. In particular, I expect all issues can be resolved without AD intervention. Some of the minor issues, if not resolved will be escalated to the AD/major issue category. Minor Issues: Minor issues are concerns about clarity or technical accuracy that should be discussed and resolved before publication, but which would normally be resolved between the authors and the reviewers. Please include all of the minor issues you have found. Give as much context information as possible (e.g., section numbers, paragraph counts). If you find no minor issues, please write: "No minor issues found." - Document's usage of "committed" vs "allocated" resources: In section 1 the document introduces the notion that the distinction between protection and restoration is based on when resources are "committed". This difference from past definition. RFC4427 and 6372 make the distinction that protection and restoration differ based on when resources are *allocated* not *committed*. To quote RFC 4427: The distinction between protection and restoration is made based on the resource allocation done during the recovery LSP/span establishment. The distinction between different types of restoration is made based on the level of route computation, signaling, and resource allocation during the restoration LSP/span establishment. This difference also leads to come confused statements in the document as well as ambiguity in the text, i.e. confusion by the reader. The term "committed" is not tightly defined in this document (or earlier work) and is used differently than how "allocated" has been used. An example of this can be found in Section 3.1 which states: However, the commitment of the resources, at least for the shared segments, will only be finalized when the protection path is actually activated. Therefore, for the purists - regarding the terminology - SMP lies somewhere between protection and restoration. Both sentences are problematic. In the first, commitment seems to cover a "protection switch" would "connect" the protection path but not the earlier "allocation" of resources. (Quoted terms are used in earlier RFCs.) The second conclusion is based on the new distinction of protection vs. restoration and is unnecessary with the existing distinction. This issue exists in multiple places in the document where "committed" is used and I'd recommend that each should be replaced with terminology used in the referenced RFCs, i.e., "allocation", "connection", "cross-connect", "protection switch(over)", ... Note I'm *not* highlighting all cases where there are problems in the document related to this issue. There are a couple of places in the document where I think it's possible that once this terminology ambiguity is corrected that I'll have other substantive comments. - Section 2, 1st paragraph, last sentence. This sentence really defines the scope/purpose of the document, i.e., "clarifies the instructions to protocol designers producing solutions that satisfy the requirements set out in this document." As such, I'd repeat this in the abstract and move it to a more pronounced place in section 1 (or 3). - General comment: fate-sharing for co-routed bidirectional LSP protection: How is co-routing preserved for the reverse path in SMP? I'd assumed the protection switch coordination protocol would be required to trigger a switchover of the reverse LSP in the co-routed case, but don't see this in the document. - In section 4 and 5.2 you reference 5712 and 3209 as defining preemption terminology and behavior. I think 6372 is the right reference here as it defines both in the context of survivability and in dependent of control plane. - In section 4.2 you say "Therefore, it is suggested that this be carried out under the control of a dynamic control plane similar to GMPLS [RFC3945]." perhaps you mean "based on GMPLS"? If so, great, please make the correction. If not, I think the debate of which control protocol is used for MPLS-TP is way beyond the scope of this document. - Section 5.1, paragraph 1. Why are you using "SHOULD NOT" here? If referring to solutions conformant with this document, then these are informative statements, "and a non-control plane based SMP switchover mechanism is used, the control plane SHALL NOT ...". If referring to an operator's/user's choice of protection mechanism, I think the most you can say is MAY. - Section 5.2. "Tie-breaking rules SHALL be defined in scope of an SMP domain." As this is a requirement, what you mean by "tie-breaking rules" should be defined directly or by reference. - Section 5.3. RFC6372 takes an approach where preemption notification leverages the standard MPLS-TP OAM mechanisms, is there any reason to do more / not just follow 6372? - Section 5.7. There may be coordination required on soft-preemption as well (depending on the cross-connects established during LSP establishment) so coordinated switching should be supported independent of preemption mode. Nits: - Abstract: I don't recall the term "executive action" being used in any earlier related/referenced RFCs. Rather than introduce a new (and undefined) term, perhaps you can use an existing one, e.g., "protection switch"? - Section 1, paragraph 1. Do we really need another definition of MPLS-TP to debate? I suggest just referencing your favorite MPLS-TP document(s) and dropping the first four sentences. The last sentence also makes a subjective statement. Whether it is critical or no is unnecessary. You can just say something like 6372 provides a survivability framework for MPLS-TP and is the foundation for this document. - Section 1, paragraph 3. Isn't the right reference 4427 not 4428? Also drop the word linear, as it is an unnecessary qualifier and 4427/4428 don't use it. - Sections 3 (and to a lesser degree section 2) are really introductory text. I'm unsure as to why they aren't part of section 1. - Section 3.2 should have a reference for "existing control plane solutions for SMP within MPLS". - Section 3.2 again uses the "executive action" term. - Section 4.1. You say "two operations simultaneously". Do you really mean "simultaneously" or merely that they must both occur for protection to be provided? (Same comment in section 5.1. - Section 5.2. I suggest numbering the currently bulletted requirements list. - Section 5.2: First paragraph and forth bullet last sentence. These both basically cover the same topic (preemption) and actually say slightly different things. I suggest combine into a single requirement to ensure consistency and full coverage of the topic. - Section 5.2, req 5. How does this relate to section 5.5? Shouldn't the topics related to timing be consolidated? - Section 5.2: requirement 6 seems to be a subset of 7, so it should be dropped. - Section 5.2, requirement 8. Isn't this a subset of 9? Why call out just this one traffic treatment (sub) requirement? - Section 5.3. s/MAY/will - section 5.4: " When the working path detects.." detection is by the node not the path. - Section 5.4, last sentence. This is only the 2nd time you imply that the document covers requirements on a new protocol. I think this point is currently too subtle in the document. (This point was also made as a minor comment.) - section 5.6. RFC 6372 should be referenced
- [RTG-DIR] RtgDir review: draft-ietf-mpls-smp-requ… Lou Berger
- Re: [RTG-DIR] [mpls] RtgDir review: draft-ietf-mp… Jeong Ryoo
- Re: [RTG-DIR] [mpls] RtgDir review: draft-ietf-mp… Lou Berger
- Re: [RTG-DIR] [mpls] RtgDir review: draft-ietf-mp… Yaacov Weingarten
- Re: [RTG-DIR] [mpls] RtgDir review: draft-ietf-mp… Lou Berger
- Re: [RTG-DIR] 회신: [mpls] RtgDir review: draft-iet… Lou Berger
- Re: [RTG-DIR] 회신: [mpls] RtgDir review: draft-iet… Lou Berger
- [RTG-DIR] 회신: [mpls] RtgDir review: draft-ietf-mp… 류정동
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- Re: [RTG-DIR] 회신: 회신: [mpls] RtgDir review: draft… Lou Berger
- [RTG-DIR] 회신: 회신: 회신: [mpls] RtgDir review: draft… 류정동
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- Re: [RTG-DIR] 회신: 회신: 회신: [mpls] RtgDir review: d… Lou Berger
- Re: [RTG-DIR] 회신: 회신: 회신: [mpls] RtgDir review: d… Jeong Ryoo
- Re: [RTG-DIR] [mpls] RtgDir review: draft-ietf-mp… Lou Berger
- [RTG-DIR] 회신: [mpls] RtgDir review: draft-ietf-mp… 류정동
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- Re: [RTG-DIR] [mpls] 회신: RtgDir review: draft-iet… Lou Berger
- [RTG-DIR] 회신: [mpls] 회신: RtgDir review: draft-iet… 류정동