Subject: Re: [lisp] Fwd: Comments about draft-cheng-lisp-shdht-01

From: [email-masked] (Noel Chiappa)
Date: Thu, 26 Jul 2012 23:59:27 -0400 (EDT)

>> From: Michael Hoefling <[email-masked]>

    >> Noel Chiappa write two drafts about the overall LISP architecture:
    >>
    >> There, it is stated that - in accordance to the standard documents -
    >> ETRs are the only authoritative source for mapping information.

Well, they are introductions, not protocol specifications, so do not expect to
see every last detail in them. And they are also initial drafts, so there
might be minor errors in them. So you should be wary of citing them as
authorities on anything! :-)

Also, in the introduction document I do in fact note there that there are
_some_ circumstances in which the MS replies on behalf of the ETR: "in some
circumstances it is advantageous to allow the MS to proxy reply on the ETR's
behalf to Map-Request messages".

    > From: [email-masked]

    > In our drat, ETRs are still the authoritative source for mapping
    > information.
    >  ...
    >  When an ETR sends a Map-Register Message requesting for the Map-Server
    >  to proxy Map-Reply, it will set the p bit to 1.
    > In our draft, SHDHT Nodes could be considered as Map-Servers which
    > implement the "Proxy Map Reply" mode.

I am not sure I understand what you mean here. Does the SHDHT node _always_
reply to the ITR on behalf of the ETR? That is what I understand from reading
the -00 version of the I-D, and you seem to confirm that above.

However, the 'proxy reply' mode is only done when the _ETR asks_ for the MS
to do it; the MS does not get to do it whenever it wants. If the ETR does not
set the 'P' bit, the MS _cannot_ proxy reply on behalf of the ETR.

This is necessary for things like 'source-specific mappings' (where an ETR
returns different mappings to different ITRs).

        Noel

---

From: Michael Hoefling <[email-masked]>
Date: Fri, 27 Jul 2012 11:10:18 +0200

Hello Noel,

> authorities on anything! :-)

Noted :)

> behalf to Map-Request messages".

I had the proxy case in the back of my head but also my understanding 
and interpretation of the current LISP drafts - and your introduction of 
course.

However, I assume that the proxy reply mode should not be the default 
operation mode.

> set the 'P' bit, the MS _cannot_ proxy reply on behalf of the ETR.

As I assumed above - no P-bit not proxy. Thanks for clarification.

> returns different mappings to different ITRs).

Isn't this possible in proxy mode as well or is the selection logic 
specific for ETRs? How is this currently achieved in DNS?

Regards,
Michael

-- 
Dipl.-Inform. Michael Hoefling, M.Sc.
University of Tuebingen
Faculty of Science
Department of Computer Science
Chair of Communication Networks
Sand 13, 72076 Tuebingen, Germany
phone: (+49)-7071/29-70507, fax: (+49)-7071/29-5220
mailto: [email-masked]
http://kn.inf.uni-tuebingen.de/staff/hoefling