Last Call Review of draft-ietf-trill-tree-selection-04
review-ietf-trill-tree-selection-04-genart-lc-sparks-2016-06-28-00

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Document: draft-ietf-trill-tree-selection-04
Reviewer: Robert Sparks
Review Date: 28 Jun 2016
IETF LC End Date: 1 Jul 2016
IESG Telechat date: 7 Jul 2016

Summary: Ready (with nits) for publication as Proposed Standard

This document is easy to read, even for someone not deeply steeped in trill.

I have a few questions and suggestions to consider



1) The essence of the idea this document provides support for is that an 


operator will create and install a configuration that meets the one tree 


per identifiable thing (such as VLAN) constraint. The protocol proposed 


here does not try to enforce that the operator supplies a configuration 


meeting that constraint. Should the things that generate messages with 


the TLVs defined in this document be restricted from sending messages 


that would map the same VLAN to two trees? I understand things will 


still work (suboptimally, as pointed out in the backwards-compatibility 


section), but it seems this configuration error should be mitigated. 


Section 3.3 also pulls the punch a little with it's discussion at the 


end of the second paragraph. If you're going to leave it up to the 


unspecified way the operator installs this configuration, you might at 


least point out that this is something to look for and complain about. 


If you think the optimal configuration isn't a likely thing to reach, 


then consider a pass through the document that sets that expectation 


consistently.






2) There are a couple of places where you use 2119 where you appear to 


be restating requirements from other documents. That's dangerous, from a 


document set maintenance point of view. Please consider changing these 


to simple prose, leaving the 2119 requirements to the protocol you're 


defining in this document. Please look at the SHOULD in the Background 


Description, and the SHOULD NOT in the first paragraph of the Overview. 


(2119 in sections like backgrounds and overviews is usually a sign that 


somethings in the wrong place.)






3) In the 3rd paragraph of 3.3, why is the requirement SHOULD strength? 


What else would the RBridge do, and when would it be reasonable for it 


to do that something else?





Nits/editorial comments:



* You use a lot of domain-specific acronyms in section 1 before saying 


what they mean in section 2.






* The first sentence in the 8th paragraph of 1.2 is very complex. (It's 


the one that starts "In cases where blocks of"). Please consider 


simplifying it.






* Section 2: (I'm no fun) Do you want this alternate expansion of FGL to 


stand?






* Figure 2: the left table has a VLAN of 4095, which is inconsistent 


with the prose.






* In section 3.4 you use 2119 RECOMMENDED (which is equivalent to 


SHOULD) when describing how the operator configures things. This isn't a 


constraint on the protocol defined in this document. Please consider 


rewriting the sentence without the 2119 keyword.






* Micronits: there's spurious space at the beginning of the 3rd line on 


page 6. There's an occurrence of BRridge that probably should have been 


RBridge in section 3.4, and "assigne" appears in the IANA Considerations.