[DNSOP] Enough latency obsession Re: Review of draft-ietf-dnsop-cookies-00

Nicholas Weaver <nweaver@icsi.berkeley.edu> Tue, 16 December 2014 19:48 UTC

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From: Nicholas Weaver <nweaver@icsi.berkeley.edu>
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Date: Tue, 16 Dec 2014 14:47:57 -0500
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To: Paul Vixie <paul@redbarn.org>
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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
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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:
> 
> 3 round trips, 7 packets, for an isolated tcp/53 query.
> 
> s   ->
>  <- s+a
> a   ->
> q   ->
>  <- r+a
> f+a ->
>  <- f+a
> 
> 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
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