Last Call Review of draft-ietf-bier-architecture-07

Request Review of draft-ietf-bier-architecture
Requested rev. no specific revision (document currently at 08)
Type Last Call Review
Team General Area Review Team (Gen-ART) (genart)
Deadline 2017-06-29
Requested 2017-06-15
Authors IJsbrand Wijnands, Eric Rosen, Andrew Dolganow, Tony Przygienda, Sam Aldrin
Draft last updated 2017-06-25
Completed reviews Rtgdir Last Call review of -07 by Susan Hares (diff)
Opsdir Last Call review of -07 by Victor Kuarsingh (diff)
Genart Last Call review of -07 by Dan Romascanu (diff)
Genart Last Call review of -08 by Dan Romascanu
Assignment Reviewer Dan Romascanu
State Completed
Review review-ietf-bier-architecture-07-genart-lc-romascanu-2017-06-25
Reviewed rev. 07 (document currently at 08)
Review result Ready with Issues
Review completed: 2017-06-25


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
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Document: draft-ietf-bier-architecture-??
Reviewer: Dan Romascanu
Review Date: 2017-06-25
IETF LC End Date: 2017-06-29
IESG Telechat date: 2017-07-06


This document specifies a new architecture known as "Bit Index Explicit Replication" (BIER) for the forwarding of multicast data packets through a "multicast domain".  It does not require a protocol for explicitly building multicast distribution trees, nor does it require intermediate nodes to maintain any per-flow state. This architecture is .  While the Abstract and Introduction of the document mentions Architecture as the principal scope, this document goes well beyond the scope of a typical architectural document. including detailed definitions of the procedures, terminology and normative algorithms required for BIER. 

The document is clear and detailed. Because of its structure, I am missing some information that usually can be found in architecture documents. I included these in the 'minor issues' list. Although none of these may be a show-stopper, I believe that addressing these before document approval can improve the quality of the document and of the overall BIER work. 

Major issues:

Minor issues:

1. As the document is targeting 'Experimental' it would be useful to mention what is the scope of the experiment. The charter actually says: 

' The scope of the experiment will be
documented in the output of the Working Group.'

Would not the Architecture document be the right place for this? If not, is there another document that deals or is planned to define the scope of the experiment? 

2. While the Abstract and Introduction of the document mentions Architecture as the principal scope, this document is different from a typical architectural document. While it defines well the procedures, terminology and normative algorithms required for BIER Intra-domain forwarding, it goes well beyond the level of detail that other similar documents go. Specifications of the procedures and normative algorithm should be mentioned in Abstract and Introduction, they occupy the same or more space than architecture. 

3. On the other hand I am missing the relationship with other work items in the BIER charter - there is no manageability section for example, there is no reference to the performance impact in networks. Maybe these are dealt with in a different document or documents or BIER, if so it would be good at least to mention and reference these here. 

4. I also would have expected the architecture document to refer the use cases document and note which of the use cases are being addressed and how - draft-ietf-bier-use-cases is not even included in the references. 

5. Sections 3 to 6 mentioned repeatedly provisioning. As there is no Operations and Manageability section as in many other Routing Area documents, it is not clear how this is expected to happen. For example draft-ietf-bier-bier-yang is not mentioned or referred. I suggest adding a note (and maybe references) for clarity.  

6. In section 8 I found: 

'Every BFR must be provisioned to know which of its interfaces lead to
   a BIER domain and which do not.  If two interfaces lead to different
   BIER domains, the BFR must be provisioned to know that those two
   interfaces lead to different BIER domains. '

It seems that the two 'must' in these sentences would rather be capitalized. 

Nits/editorial comments: