Re: [DNSOP] Priming query transport selection
Nicholas Weaver <nweaver@ICSI.Berkeley.EDU> Thu, 14 January 2010 16:40 UTC
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From: Nicholas Weaver <nweaver@ICSI.Berkeley.EDU>
Date: Thu, 14 Jan 2010 08:40:10 -0800
To: Patrik Fältström <patrik@frobbit.se>
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Cc: Ray.Bellis@nominet.org.uk, dnsop@ietf.org, Nicholas Weaver <nweaver@ICSI.Berkeley.EDU>
Subject: Re: [DNSOP] Priming query transport selection
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On Jan 14, 2010, at 7:58 AM, Patrik Fältström wrote: > > 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). > > It is enough problems with the 512 limit of today. I do not want to have the same problems when we pass 4096. > > Implementations should be free to choose an implementation limit smaller if they want to (and signal that in the EDNS0 size), but please do not say that "max value on EDNS0 size will forever be 4096" or something similar. > > Be careful with the wording... Except that EDNS0 MTU is closely coupled with the UDP protocol and its unreliable nature: this message MTU is irrelevant for TCP or another reliable protocol. It is highly unlikely that the network's MTU will expand beyond 1500B: There is too much Ethernet, and >1500B MTUs don't really benefit things anyway, because the overhead reductions of going to a higher MTU are near zero (Amdahl's law). Which means the number of fragments which ALL need to be received correctly goes up linearly with the size of the message. Even WITH a larger MTU, bit-errors become more common. So, even at a minimum, you'd expect many more failures, dropped packets, etc, with a 40,000B datagram than a 4000B datagram. And DNS over UDP is already unreliable enough, at least when you consider it all the way to the end host with a reasonable timeout on lookups. Thus given the nature of the UDP protocol, it is highly unlikely that you'd ever want to do ~10K+ byte UDP datagrams.
- [DNSOP] Priming query transport selection Olafur Gudmundsson
- Re: [DNSOP] Priming query transport selection Jim Reid
- Re: [DNSOP] Priming query transport selection Alex Bligh
- Re: [DNSOP] Priming query transport selection Alex Bligh
- Re: [DNSOP] Priming query transport selection Jim Reid
- Re: [DNSOP] Priming query transport selection Alex Bligh
- Re: [DNSOP] Priming query transport selection Alfred Hönes
- Re: [DNSOP] Priming query transport selection Jim Reid
- Re: [DNSOP] Priming query transport selection Olafur Gudmundsson
- Re: [DNSOP] Priming query transport selection Alex Bligh
- Re: [DNSOP] Priming query transport selection Edward Lewis
- Re: [DNSOP] Priming query transport selection Alex Bligh
- Re: [DNSOP] Priming query transport selection Jim Reid
- Re: [DNSOP] Priming query transport selection Olafur Gudmundsson
- Re: [DNSOP] Priming query transport selection Jaap Akkerhuis
- Re: [DNSOP] Priming query transport selection Olafur Gudmundsson
- Re: [DNSOP] Priming query transport selection Jaap Akkerhuis
- Re: [DNSOP] Priming query transport selection Nicholas Weaver
- Re: [DNSOP] Priming query transport selection Ray.Bellis
- [DNSOP] RSA cracking Jim Reid
- Re: [DNSOP] Priming query transport selection Patrik Fältström
- Re: [DNSOP] Priming query transport selection bmanning
- Re: [DNSOP] Priming query transport selection Nicholas Weaver
- Re: [DNSOP] Priming query transport selection Patrik Fältström
- Re: [DNSOP] Priming query transport selection Sebastian Castro
- Re: [DNSOP] Priming query transport selection Ray.Bellis
- Re: [DNSOP] Priming query transport selection Simon Leinen
- Re: [DNSOP] Priming query transport selection Florian Weimer
- Re: [DNSOP] Priming query transport selection Jim Reid
- Re: [DNSOP] Priming query transport selection Florian Weimer
- Re: [DNSOP] Priming query transport selection George Barwood
- Re: [DNSOP] Priming query transport selection George Barwood
- [DNSOP] signing glue and additional data Jim Reid
- Re: [DNSOP] signing glue and additional data George Barwood
- Re: [DNSOP] Priming query transport selection Sebastian Castro
- [DNSOP] on what glue is (was: signing glue and ad… Andrew Sullivan
- Re: [DNSOP] on what glue is (was: signing glue an… Roy Arends
- Re: [DNSOP] [dnsext] Re: Priming query transport … Danny Mayer
- Re: [DNSOP] [dnsext] Re: Priming query transport … Alfred Hönes
- Re: [DNSOP] [dnsext] Re: Priming query transport … Olafur Gudmundsson