Re: [lisp] Gen-ART IETF Last Call review of draft-ietf-lisp-ddt-08

[[e-mail] (Dale R. Worley)]

Dino Farinacci <[e-mail]> writes:
>> Both of these servers process Map-Request messages, albeit with
>> different semantics.  Hence the D bit in Map-Request messages is needed
>> to differentiate which server is to process a given Map-Request message.
>
> The reason I explained the above was that the D-bit tells the receiver
> of a Map-Request what type of message to return regardless of the
> colocation status of the servers.

OK, that's close to the distinction I was making.  The defining text is
probably from section 5:

   D: The "DDT-originated" flag.  It is set by a DDT client to indicate
      that the receiver SHOULD return Map-Referral messages as
      appropriate.  Use of the flag is further described in
      Section 7.3.1.  This bit is allocated from LISP message header
      bits marked as Reserved in [RFC6830].

But when I read it, the phrase "the receiver SHOULD return Map-Referral
messages as appropriate" wasn't at all clear.  I assume now that what it
means is, "should return Map-Referral messages *as described in this
document*, whereas D=0 means it should be processed as described in RFC
6833".  The defining characteristic isn't the type of messages to be
returned but which processing to apply, as a DDT server and a Map-Server
are very different things (defined in different RFCs!).

Dale