Re: [DNSOP] Priming query transport selection

Patrik Fältström <patrik@frobbit.se> Thu, 14 January 2010 17:14 UTC

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From: Patrik Fältström <patrik@frobbit.se>
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Date: Thu, 14 Jan 2010 19:14:11 +0200
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Subject: Re: [DNSOP] Priming query transport selection
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On 14 jan 2010, at 17.58, Patrik Fältström wrote:

> On 14 jan 2010, at 10.38, Ray.Bellis@nominet.org.uk wrote:
> 
>>> EDNS0 RFC restricts EDNS0 to 4096 bytes, number of implementations
>>> will not send more even if client ask for it. Firewalls will
>>> enforce this.
>> 
>> RFC 2671 enforces no such limit - the strict limit is 65535, and §4.5.5 
>> has a hint that 4K might be a reasonable amount of state to maintain for 
>> fragment reassembly.
>> 
>> I seem to recall that BIND, however, will not permit the EDNS0 buffer size 
>> to be configured above 4096.  I'm not in a position to double check that 
>> right now, though.
> 
> Please do not start talking about enforcing some fixed limit that we will laugh about 10 years from now... And if you talk about a limit, pick something very large (like 65535 that seems to be already chosen).

Let me clarify (and send excuses to Ray) that my comment was not directed against what he said, but supporting him, and instead argue against what some others have suggested -- a fixed low number.

   Patrik -- with left foot in mouth