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From: Nicholas Weaver <nweaver@icsi.berkeley.edu>
In-Reply-To: <549069CC.20309@redbarn.org>
Date: Tue, 16 Dec 2014 14:47:57 -0500
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Message-Id: <C8B63370-255E-483E-819B-AAB688654A0E@icsi.berkeley.edu>
References: <20141216152511.GA22255@totoro.home.mukund.org>
 <20141216171318.GA23468@totoro.home.mukund.org> <549069CC.20309@redbarn.org>
To: Paul Vixie <paul@redbarn.org>
Archived-At: http://mailarchive.ietf.org/arch/msg/dnsop/57vQvZQuowDw9Fhqd7vfRcWy51o
Cc: dnsop@ietf.org, Mukund Sivaraman <muks@isc.org>,
 Nicholas Weaver <nweaver@icsi.berkeley.edu>
Subject: [DNSOP] Enough latency obsession Re: Review of
 draft-ietf-dnsop-cookies-00
Precedence: list


Its time to stop obsessing over latency in DNS!

DNS doesn't exist in a vacuum, but then goes to at minimum, a TCP =
handshake, and who knows what else beyond it.  Amdahl's law matters.

How many headaches would go away if all DNS is over TCP?  And how much =
would it really make a difference in Latency?


> On Dec 16, 2014, at 12:20 PM, Paul Vixie <paul@redbarn.org> wrote:
>=20
> 3 round trips, 7 packets, for an isolated tcp/53 query.
>=20
> s   ->
>  <- s+a
> a   ->
> q   ->
>  <- r+a
> f+a ->
>  <- f+a
>=20
> obviously, the dickenson tcp change proposal bears on this, but today, =
it's 3 rtt, 7 pkt, and that's assuming that the response fits in one =
window. axfr is obviously much longer.

And this is wrong:  The f+a RTT doesn't matter, thats AFTER the result =
has been received.  TCP is 2 RTT to actually get the result.

--
Nicholas Weaver                  it is a tale, told by an idiot,
nweaver@icsi.berkeley.edu                full of sound and fury,
510-666-2903                                 .signifying nothing
PGP: http://www1.icsi.berkeley.edu/~nweaver/data/nweaver_pub.asc