Subject: Re: Time to make some progress: EDNS0

From: Jeff Schreiber <[email-masked]>
Date: Thu, 20 May 1999 07:27:14 -0400

Paul A Vixie <[email-masked]> writes:
>
> If a responder does not implement the VERSION level of the request, then it
> answers with RCODE=BADVERS.  All responses will be limited in format to the
> VERSION level of the request, but the VERSION of each response will be the
> highest implementation level of the responder.  In this way a requestor will
> learn the implementation level of a responder as a side effect of every
> response, including error responses, including the RCODE=BADVERS response.

    What about using this sort of model.  The resolver uses the highest
    version that it can use. If the server doesn't know that version, it
    responds with BADVERS, and has the highest version it supports in the
    response.  The resolver can then use that version.

    It saves a lot of confusing parsing for 'what version do I need?', and
    also allows the use of higher versions which may do the same things
    better.
                                    -Jeff

---

From: Andras Salamon <[email-masked]>
Date: Fri, 21 May 1999 14:55:34 +0200

>     response.  The resolver can then use that version.

Is this meant to imply a dependency between versions, where if I want
to code to the latest version M, then I need to add to the code all
information about earlier versions, too?

Paul's text
    the VERSION of each response will be the highest implementation
    level of the responder.  In this way a requestor will learn the
    implementation level of a responder
seems to assume that all versions from 0 to N will be supported, where N
is the highest supported.  The alternative seems to be to either retry the
query with a lower VERSION, until a common version is found (this is just
a merge of two sorted lists and may take N/2 queries to find that there
are no matches, in the case of one party supporting even version numbers,
the other party odd numbers), or to back off to vanilla DNS straight away.

What was the original intention?

-- Andras Salamon                   [email-masked]

---

From: Paul A Vixie <[email-masked]>
Date: Mon, 24 May 1999 11:17:27 -0700

> information about earlier versions, too?

yes.

> What was the original intention?

yes.