Subject: Re: [dnsext] draft-ietf-dnsext-dns-tcp-requirements-00 / a way forward

From: Doug Otis <[email-masked]>
Date: Mon, 19 Oct 2009 11:08:44 -0700

There seems to have been an outage of the namedropper mailing list.
This message is being resubmitted, as it appears to have been lost.

-------- Original Message --------
Subject: Re: [dnsext] draft-ietf-dnsext-dns-tcp-requirements-00 / a way 
forward
Date: Fri, 16 Oct 2009 11:24:56 -0700
From: Doug Otis <[email-masked]>
To: [email-masked]
CC: Paul Vixie <[email-masked]>, [email-masked]

On 10/16/09 1:05 AM, [email-masked] wrote:
>
>  > does the current draft make it clear that tcp is (and has always been)
>  > mandatory AND that it is (and has always been) a backup or secondary
>  > transport (after UDP/EDNS)?
>
> It's not quite as explicit as that.
>
> It points out that in 1035 and 1123 it was "SHOULD", but that 1123
> predicted a time when it would become "required" (non-2119 required).
>
> So this draft changes that into "REQUIRED" except in a small set of edge
> cases.
>
> It does not attempt to make TCP a primary transport, with the caveat
> that it says: "A resolver SHOULD send a UDP query first, but MAY elect
> to send a TCP query instead if it has good reason to expect the response
> would be truncated if it were sent over UDP, or for other operational
> reasons."

A reality of dependence needs to be clarified.  There remains a urgent
need to better deal with TCP's potential for causing inordinate and
disproportionate burdens on DNS servers that are unlikely to be met.  A
strong cautionary statement warning that "TCP SHOULD receive lower
resource priority during aberrant demand to ensure UDP operation" could
help clarify the limited reliance safely placed upon the use of TCP with
DNS.

Unfortunately, even this type of warning seems unlikely at preventing a
degradation of availability.  The overarching problem of security
inducing the change to DNS can largely be solved by modern transport.
Transports used at recursive resolvers represent a secondary problem
that may never change.

-Doug