[OSPF] AD review of draft-ietf-ospf-ospfv3-lsa-extend

[Alia Atlas <[e-mail]>]

As is customary, I have done my AD review of
draft-ietf-ospf-ospfv3-lsa-extend-19.  First, I would like to thank the
authors - Acee, Abhay, Dirk, Veerendranatha, and Fred- and the implementors
at Nokia and Huawei (who have enabled us to move forward on this critical
document) and the WG.  This draft is very important for adding improved
flexiblity to OSPFv3 for IPv6 compared to what we enjoy for OSPFv2.

I do have some minor concerns and nits - as listed below. I am going to put
this document into a 3 week IETF Last Call (given the holiday season) and
place it on the telechat for Jan 25, 2018.  Please do respond and update
the draft in a timely fashion (given I'm on vacation until 2018).

1)  Given the extensive changes to OSPFv3 and the expectation that
implementations of OSPFv3 will support this, the draft should update RFC
5340 (and mention that in the abstract as well).

2) In Sec 3: it would be helpful to indicate how many levels of nesting of
TLVs are supported.  There are clearly TLVs and sub-TLVs.  Can there be
sub-sub-TLVs?  Can there be an arbitrarily deep level of sub-TLVs?  Please
just clarify - b/c it can affect folks implementations and also assumptions
for how to define the various sub-TLVs.

3) Sec 3.3: Is there a reason that sub-TLVs aren't listed in the figure?  I
see them in the figures for sec 3.2 and 3.4 without explanation.
Consistency would be good. I could picture it being helpful to include, for
instance, an SRLG or other information.

4) Sec 4.1: Please clarify whether an E-Router-LSA is malformed if it does
not contain at least one Router-Link TLV.

5) Sec 4.7: I believe it is possible to have multiple IPv6 link-local
addresses. I do see that RFC 5340 restricted OSPFv3 to advertising just
one.  Is there a strong reason that if additional are sent  "Instances
following the first MUST be ignored." ?  Perhaps this could be a SHOULD -
to allow for flexibility?

6) Sec 5: "an LSA MUST be considered malformed if it does not include any
required TLV or Sub-TLVs."  should be "...not include all of the required
TLVs or sub-TLVs." or the equiv.

7) Sec 6.2: "Furthermore, the extended LSAs will only include those TLVs
which require further specification for that new functionality.  Hence,
this mode of compatibility is know as "sparse-mode"."  How does this
interact with the Sec 5 that talks about malformed LSAs?  It seems like
either this would be additional Extended LSAs (not defined in this draft)
or it would have to include the mandatory information (but not for all
links/ routers).

8) Sec 8.2: Is there a reason to not have a sub-TLV range for either Expert
Review or FCFS?  There are a lot of values - and this would support
experimentation.

9) Since this document is adding the "N" flag - an example for the usage
would be helpful - and particularly articulating how it is different from
the "LA" flag for usage.

Nits:

a) Sec 3.1.1:  sentence missing a complete verb  "The N-bit is to the
Inter-Area-Prefix-TLV   (Section 3.4), External-Prefix-TLV (Section 3.6),
and Intra-Area-
   Prefix-TLV (Section 3.7)"
b) typos: differnt  addtional

Regards,
Alia