Subject: Re: [dnsext] EDNS Ping fallbacks

From: Andrew Sullivan <[email-masked]>
Date: Mon, 1 Jun 2009 13:32:29 -0400

[no hat]

On Sun, May 31, 2009 at 06:16:40PM +0100, George Barwood wrote:

> This is true for a naive use of EDNS Ping, but it does not mean EDNS
> Ping is not useful.

I think you're framing the question in the wrong terms, there.  It
seems to me that several of the critics of EDNS0 Ping are not outright
saying, "It can't be useful," but instead, "The gains are not worth
the additional cost."

Some of the critics are arguing that the gains amount to nothing, in
that it is possible for an attacker to force a downgrade.  In
response, you offer that EDNS0 Ping could be part of a set of
heuristics that allow for intelligent reaction in the absence of
DNSSEC.  So, for instance,

> (3) Adopt more complex fallbacks, such as comparing multiple
> responses to infer a safe result, or a restrictive ( but less
> efficient ) cache policy.
> 
> Clients may also maintain state information to minimise the number
> of extra packets required.

At this point, it seems to me, you have to make a pretty compelling
argument that EDNS0 Ping will in fact help, since what you are arguing
is that we deploy several different complementary strategies in an
attempt to detect badness.  It will be necessary, of course, not only
to specify all these technologies, but also to specify which
interactions are an indication of badness, and so on.  The time it
might take to come to consensus on how these things might work and how
the interactions are strong evidence of badness (as opposed to broken
implementations, &c.) is not obviously smaller than the time to
deploy DNSSEC to the point where it might be practically useful.

Best,

A

-- 
Andrew Sullivan
[email-masked]
Shinkuro, Inc.

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