[Lsr] John Scudder's No Objection on draft-ietf-lsr-ospf-prefix-originator-11: (with COMMENT)

[John Scudder via Datatracker <[e-mail]>]

John Scudder has entered the following ballot position for
draft-ietf-lsr-ospf-prefix-originator-11: No Objection

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COMMENT:
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Thanks for the update to the document and the discussion. Many points are
resolved, remaining discussion summarized below. And by the way, I wondered the
same as Ben regarding "In the ECMP case is there a way to correlate (order of
appearance?) the listed router-IDs with the listed reachable addresses?"

1. I've cleared my discuss but as mentioned in earlier email, would still
suggest an update to the abstract:

"I would prefer to see a sentence in the abstract as well, since for some
people the abstract is the only look they’ll take at the document and for them,
the question of “what is it for?” isn’t answered. I don’t insist on this, but I
recommend it. The additional sentence, if you choose to add it, could be
something like “this information does not change route computation but is
expected to be useful for network analysis and troubleshooting”."

2. Section 2.1:

   For intra-area prefix advertisements, the Prefix Source OSPF Router-
   ID Sub-TLV MUST be considered invalid and ignored if the OSPF Router
   ID field is not the same as Advertising Router field in the
   containing LSA.  Similar validation cannot be reliably performed for
   inter-area and external prefix advertisements.

As discussed with Ketan, I'm not sure if "ignored" is vague only to me, or if
it might be to other readers of the spec. I leave it to the authors' discretion
whether and how to elaborate.

4. Section 3:

   When an ABR generates inter-area prefix advertisements into its non-
   backbone areas corresponding to an inter-area prefix advertisement
   from the backbone area, the only way to determine the originating
   node information is based on the Prefix Source OSPF Router-ID and
   Prefix Source Router Address Sub-TLVs present in the inter-area
   prefix advertisement originated into the backbone area by an ABR from
   another non-backbone area.  The ABR performs its prefix calculation
   to determine the set of nodes that contribute to the best prefix
   reachability.  It MUST use the prefix originator information only
   from this set of nodes.  The ABR MUST NOT include the Prefix Source
   OSPF Router-ID or the Prefix Source Router Address Sub-TLVs when it
   is unable to determine the information of the best originating node.

What is it supposed to do if there are N contributing routes but it can only
determine the information for M < N of the contributors?

Ketan replied (my paraphrase) that in such a case partial information is sent.
My further question was "OK. And it’s considered fine that that information for
some, but not all, of the contributors is included? It seems potentially
problematic that the route only includes partial information, but the consumer
of the route has no way to know this. The other obvious choices would have been
to omit the information altogether if only partial information was available,
or to mark it as partial somehow."