Subject: [lisp] Issue Title (number): Returning all 3 prefixes (105)

From: Darrel Lewis <[email-masked]>
Date: Tue, 20 Jul 2010 14:53:45 -0700

Issue Title (number): Returning all 3 prefixes (105)
Draft Section: 6.1.5
Issue Description: 
Comments:

Section 6.1.5 EID-to-RLOC UDP Map-Reply message

    A Map-Request for EID 10.1.5.5, would cause a Map-Reply with a record
    count of 3 to be returned with mapping records for EID-prefixes
    10.1.0.0/16, 10.1.1.0/24, and 10.1.2.0/24.

Why would those three prefixes be returned? A more general comment is that what a Map-Reply must return in response to a given Map-Request is underspecified (or the specification is not comprehensible).

To address this perhaps insert something like the following:

    "When an ETR replies to a Map-Request, it must reply with its
    EID-prefix that is the best match for the Map-Request. In addition,
    if it is configured with any EID-prefixes which are more-specifics
    of the best match EID-prefix that it returns in its Map-Reply, it
    must return all of those more-specific EID-prefixe s in the same
    Map-Reply".

Response:

Dear Yakov-

Thank you for your contribution to draft-ietf-lisp-06.txt. The draft authors
have reviewed your comments but do not feel that changes to the document are
warranted at this time. In your first point, three prefixes are returned 
because there may be more specific prefixes that want to use a different 
locator-set.  In response to your suggested behavior, we don't think this 
will work because for one EID the best match may be the /16, and if a 
packet is sent to another EID that matches the /24, the ITR won't send 
a Map-Request for it because it is satisfied with the /16. That will 
result in the locator-set for the /24 cannot be used.  (As an aside, 
here was a long thread on the required behavior of 'nested EID prefixes 
on the WG mailing list.)   Please feel free to continue discussion of 
your issue on the LISP working group mailing list, [email-masked]. 
Should discussion result in WG consensus that changes are required, 
the authors will incorporate appropriate text into a future version 
of the draft.

	Thanks!
	Darrel, for the LISP document authors