Last Call Review of draft-ietf-mpls-ldp-ipv6-14
review-ietf-mpls-ldp-ipv6-14-opsdir-lc-chown-2015-02-05-00

I have reviewed this document as part of the Operational directorate's

ongoing effort to review all IETF documents being processed by the

IESG. These comments were written with the intent of improving the

operational aspects of the IETF drafts. Comments that are not addressed

in last call may be included in AD reviews during the IESG review.

Document editors and WG chairs should treat these comments just like

any other last call comments.

Summary: this document is Ready with Issues.


This document describes updates to the Label Distribution Protocol as

described in RFC 5036 (and GTSM elements in RFC 6720), to clarify and

correct the described or implied behaviour in IPv4-only, IPv6-only and 

dual-stack deployments.

Issues:

* This draft describes a number of ambiguities in particular in dual-stack

behaviour, with at least eight such issues being listed in section 1. When

reading this draft, in conjunction with RFC 5036, I personally find it quite

tricky to apply the updated rules/guidance described here to the existing

text in RFC 5036, due to the rather patchy nature of the document. I would 

therefore suggest that the authors consider a complete revision to 

RFC 5036 (as happened from RFC 3036), rather than having the 

clarifications / corrections ‘dangling’ in this additional text. I appreciate

that such a revision may be considered overkill, so at the very least this 

document should include a clear list of changes / updates, perhaps as 

an appendix.

* The general principles of the dual-stack / IPv4 / IPv6 operation should

be stated early in the document - these are conveyed piece by piece as 

you read through the document, but it would be helpful to have them 

clearly stated up front. 

* There is an amount of repetition through the document. I suspect that in

the 15 revisions there have been changes made which have caused this.

If the document progresses as a standalone document, this should be 

corrected where possible.  As it stands, the document feels disjoint in 

places, and doesn’t flow anywhere near as well as it could.

Nits:

* The specification language section (section 2) should be moved earlier in 

the document, given abbreviations described therein are used prior to their

definition.

* In 5.1 may wish to mention the IANA registry for IPv6 multicast addresses

http://www.iana.org/assignments/ipv6-multicast-addresses/ipv6-multicast-addresses.xhtml

* Last para of 5.1 - why are IPv6 LDP link Hellos to be transmitted first?

It would be useful to state the reason.

* There are various places in the draft that talk about address selection,

e.g. in 5.1 and in 5.2; I think these are all consistent with RFC 6724, so 

perhaps that RFC should be used / cited here?

* The set of rules in 6.1 repeats some parts of the earlier sections, but not

entirely, e.g. the rule in the last para of 5.1 is not included in 6.1. 

* In 6.1.1, para 2, state here that this inclusion of the new TLV is a MUST;

this is currently only stated a further page on.

* In 6.1.1 point 3a) this is a little confusing because earlier the document 

talks about sending both IPv4 and IPv6 Hello messages, and part c) seems

to duplicate parts a) and b) ?

Tim