I am the assigned Gen-ART reviewer for this draft. The General Area Review Team (Gen-ART) reviews all IETF documents being processed by the IESG for the IETF Chair. Please treat these comments just like any other last call comments. For more information, please see the FAQ at < http://wiki.tools.ietf.org/area/gen/trac/wiki/GenArtfaq>. Document: draft-ietf-teas-rsvp-te-srlg-collect-02.txt Reviewer: Elwyn Davies Review Date: 2015/09/13 IETF LC End Date: 2015/09/24 IESG Telechat date: (if known) - Summary: Not ready for publication. The main problem appears to be that the use of SRLG ID RRO sub-objects in Resv messages seems to be an afterthought. It needs to be covered in the introduction. It is also not clear how nodes are informed that SRLG information needs to be added to Resv messages. I am also concerned that the ordering constraints imposed on RRO sub-objects by various different standards (at least this one and RFC 7571 - there may be others that I am not aware of) may become overly complex and potentially mutually incompatible. When I reviewed the draft that subsequently became RFC 7571 earlier this year there were already internal issues with sub-object ordering that had to be sorted out - checking that ordering constraints do not result in a deadly embrace could get quite complicated if more specifications add to the RRO stack. Major issues: What is an SRLG ID? OK, it is a 4 octet (opaque) data item. However, the specification says nothing about how it might be used to convey the SRLG information. I *guess* that this may be because this is just a handy facility that can be used in whatever way an implementation chooses - but if so it would good to say this. Maybe an example of how the authors envisage it might be used, maybe in the context of the use case in s1.1 would be helpful. s4.1: The SRLG Collection flag is meaningful on a Path message. If the SRLG Collection flag is set to 1, it means that the SRLG information SHOULD be reported to the ingress and egress node along the setup of the LSP. I am unclear how the Path message is going to impart SRLG information to both ends of the LSP as my understanding of RSVP is that the Path message travels only in one direction along the path of the LSP. ... Ah, when I read down towards the end of s5.1, it appears that the SRLG info may be in Resv messages as well, and might be collected during the processing of the Resv message along the (reverse) path. According to RFC 3209, the presence of an RRO in the Path message will trigger the addition of an RRO to the Resv message, but this does not tell the nodes that SRLG information ought to be added. Presumably the SRLG Collection flag should be set somewhere in a suitable place in the Resv message also. But where? The text above says the flag is only meaningful on Path messages!! Maybe the RRO Attributes sub-object might be relevant [RFC5420]. The draft needs to talk about both directions and uni-/bidirectional LSPs from an earlier point in the document. Minor Issues: s5: RRO Sub-object ordering constraints. In s4.2, a number of ordering constraints are specified indicating where the SRLG info objects should be placed in the stack of RRO sub-objects. Section 5 does not discuss what should happen if the receiving node detects that the sub-objects don't match the specified ordering constraints. A more general issue is whether there are interactions with ordering constraints from other specifications that use RRO sub-objects - for example, RFC 7571 has some quite complex ordering constraints. There is also the following text in s5.1: o For Path and Resv messages for a bidirectional LSP, a node SHOULD include SRLG sub-objects in the RRO for both the upstream data link and the downstream data link from the local node. In this case, the node MUST include the information in the same order for both Path messages and Resv messages. That is, the SRLG sub- object for the upstream link is added to the RRO before the SRLG sub-object for the downstream link. It strikes me that using one of the reserved bits in the SRLG sub-object to explicitly identify whether a sub-object applies to the upstream or downstream direction would make things less error prone and reduce the ordering constraint which might get quite complicated as time goes on if new RRO sub-objects continue to be added. Nits/editorial comments: General: Just checking: does this specification apply to basic MPLS or only to the extended Generalized MPLS? It would be good to be clear about the scope up front. General: Bringing out the IANA temporary allocations at every point where they apply in Sections 4.1, 4.2, 5.1 and 8 is undesirable as it will have to be edited out by the RFC Editor increasing the scope for error. OK this is not a big risk but it would simplify things if the body text had the expected final form and the temporary allocation text notes were confined to a special section that was marked for removal by the RFC Editor. General: s/byte/octet/g Abstract: Probably ought to mention (G)MPLS explicitly and expand TE. s1, para 1: It would be good to expand TE explicitly (as Generalized MPLS Traffic Engineering) again. s3: Using RFC 2119 language here is inappropriate - they are design/usage issues not testable protocol features. s4.1, para 1: s/indicate nodes/indicate to nodes/ s4.1 and s4.2, last para in each case: s/The rules of the/The rules for the/ (2 places) s5.1, paras 2 and 3: s/and the SRLG Collection Flag set/with the SRLG Collection Flag set/ (2 places) s5.1, last para: Need to expand FA acronym. s6.1: It would be useful to repeat the policy configurations mentioned in s5 in this section. s6.2, para 1: s/SRLG ids/SRLG IDs/ [please check that there aren't any other cases].