Re: [dns-privacy] DNS over DTLS

Tariq Saraj <tariqsaraj@gmail.com> Fri, 02 December 2016 13:32 UTC

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References: <CAAdbxrrgKRvUUgWQUFvxQiwua_DsochdZm83pi_Zgx_wo4-GPg@mail.gmail.com> <20161201150121.5be7b162@pallas.home.time-travellers.org> <CAAdbxro1Cu-MAW+kYe3YE0YPb27TjVPOdLtA_jF=0=OQgmCcHw@mail.gmail.com> <87h96mvnba.fsf@alice.fifthhorseman.net>
From: Tariq Saraj <tariqsaraj@gmail.com>
Date: Fri, 2 Dec 2016 18:32:09 +0500
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To: Daniel Kahn Gillmor <dkg@fifthhorseman.net>
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Cc: Shane Kerr <shane@time-travellers.org>, dns-privacy@ietf.org
Subject: Re: [dns-privacy] DNS over DTLS
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HI Daniel,
So true, and thank you very much.... also thanks to Shane....

On Fri, Dec 2, 2016 at 11:48 AM, Daniel Kahn Gillmor <dkg@fifthhorseman.net>;
wrote:

> On Fri 2016-12-02 01:22:40 -0500, Tariq Saraj wrote:
> > Thanks for your detailed reply, the point I am trying to highlight is the
> > changes in TCP for DNS which is "TCP out of order packet delivery, i.e.
> the
> > OOOP".
>
> I think you're referring to "out of order processing" for DNS requests
> by a recursive resolver.  While necessary for reasonable performance
> over TCP, I don't think this approach remediates TCP
> head-of-line-blocking.
>
> imagine a client who makes two queries across a TCP connection in rapid
> succession, the first for slow.example and the second for fast.example.
>
> many traditional (old, unoptimized) DNS recursive resolvers will try to
> find the answer for slow.example before they even start making the
> queries needed for fast.example.  they might not even read the second
> query from the TCP connection before responding to the first one.
>
> OOOP says that a DNS recursive resolver should read queries as they come
> in over TCP, even if it still has responses pending for other queries
> from that connection.
>
> IOW, the dns resolution *itself* should not block based on slow DNS
> responses from the authoritative servers it queries.
>
> but none of that resolves the problem of TCP head-of-line blocking.  if
> one packet carrying a query on one TCP connection gets dropped, the
> receiving server can't see any of the rest of the packets until the
> earlier packet is re-sent.  (and vice versa for replies going from
> recursor to stub)
>
> does this make sense?
>
>          --dkg
>



-- 
Regards
Tariq Saraj
Riphah Institute of Systems Engineering, Islamabad