[OSPF] early AD review of draft-ietf-bier-ospf-bier-extensions-07

[Alia Atlas <[e-mail]>]

I have done an early AD review of draft-ietf-bier-ospf-bier-extensions-07
in preparation for the publication request.

First, I would like to thank the many authors for their work on this draft.
Given that there are currently 7 authors listed, I'd recommend appointing a
few editors or otherwise reducing down to 5 or fewer. Of course, I am also
willing to consider extraordinary circumstances where the shepherd can
explain to me privately the deep technical contribution made by each author.

I do see a number of major issues.

Major Issues:

1)  RFC7684 is just for OSPFv2.  How is the information carried for OSPFv3?
We need a mechanism that works for IPv6 also.

2) In Sec 2.1, the Length is defined as variable and the figure includes
additional sub-TLVs. Please clarify in the text what other sub-TLVs can be
carried & how the length is calculated (yes, same as always - but clarity
helps with interoperability).

3) Sec 2.2 "The size of the label range is determined by the number of Set
      Identifiers (SI) (section 1 of [I-D.ietf-bier-architecture]) that
      are used in the network.  Each SI maps to a single label in the
      label range.  The first label is for SI=0, the second label is for
      SI=1, etc.:

This implies that there is no way to indicate only a label for SI=1 or a
range for SI=1 to 3. That seems unfortunate and assumes that the BFR-ids
are always allocated from SI=0 up.   Is there a reason not to use some of
the reserved bits to indicate the starting SI value?

4) Sec 2.3: The Tree type is a 1 octet value - that doesn't appear to have
any IANA allocation or meaning clearly indicated - beyond the parenthetical
that 0=SPF.  Please fix this.

5) Sec 2.5: This section could benefit greatly from a diagram - showing the
advertising router for a prefix, the ABR, and what is then flooded for the
BIER MPLS Sub-TLV for the new areas.

Minor:

4) Sec 2.3: "Label Range Base: A 3 octet field, where the 20 rightmost
bits represent the first label in the label range."  What about the top 4
bits?  Are they Must Be Zero (MBZ)?  How about making that explicit?  Are
they potential future flags?/

Thanks,
Alia