Re: [Doh] [Ext] DNS Camel thoughts: TC and message size
Tony Finch <dot@dotat.at> Thu, 07 June 2018 10:33 UTC
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Date: Thu, 07 Jun 2018 11:33:21 +0100
From: Tony Finch <dot@dotat.at>
To: Paul Hoffman <paul.hoffman@icann.org>
cc: DoH WG <doh@ietf.org>, bert hubert <bert.hubert@powerdns.com>
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Subject: Re: [Doh] [Ext] DNS Camel thoughts: TC and message size
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Paul Hoffman <paul.hoffman@icann.org> wrote: > > DNS-over-TCP is defined in RFC 1035 and significantly updated in RFC > 7766. Unless I'm missing something, neither of those document support > the 65535 length restriction; The restriction comes from the 2 octet message length field, RFC 1035 section 4.2.2. > in fact, RFC 1035 section 3.3.10 indicates that restriction doesn't > exist because a response with a single maximally-sized NULL Rdata record > could be slightly longer than that, and there is no restriction on how > many NULL records can be in the RRset. Right. You need to make a distinction between RR data size limits and message size limits. As you say, it's easily possible for an RRset to be too long to fit in a message. If a single RR doesn't fit in a message then it isn't possible to create it via UPDATE or transfer it via AXFR/IXFR, though it can be represented in master files. It's clear such large RRs are not supported by the standards - I guess they don't specify how to cope because huge RRs are an obviously lunatic idea ;-) > So, if this WG puts such a limitation in DOH, we are adding a > restriction to DNS messages that is not currently in DNS-over-TCP, even > though it is a "sensible" restriction. No, the message size limit was always there, even though it is smaller than the RR data size limit. This was the point of Bert's message. As he said, lifting the 64K limit means "almost every DNS parser in existence has become obsolete or at least untested! No DNS message larger than 64KB has ever been possible." > DNS message truncation and the use of the TC bit should > be handled as if the response was carried over DNS > in TCP as defined in [RFC7766]. EDNS buffer sizes need to be handled the samee as for TCP as well. Tony. -- f.anthony.n.finch <dot@dotat.at> http://dotat.at/ Shannon, Rockall, Malin, South Hebrides: Northerly or northeasterly, 3 or 4, occasionally 5 later. Slight or moderate. Mainly fair. Moderate or good, occasionally poor.
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- Re: [Doh] [Ext] Are we missing an architecture? (… Petr Špaček
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- Re: [Doh] [Ext] Are we missing an architecture? (… Ray Bellis
- Re: [Doh] [Ext] Are we missing an architecture? (… Dave Lawrence
- Re: [Doh] [Ext] Are we missing an architecture? (… Dave Lawrence
- Re: [Doh] [Ext] Are we missing an architecture? (… Paul Hoffman
- Re: [Doh] [Ext] Are we missing an architecture? (… Tom Pusateri
- [Doh] DNS Camel thoughts: TC and message size bert hubert
- Re: [Doh] DNS Camel thoughts: TC and message size Petr Špaček
- Re: [Doh] DNS Camel thoughts: TC and message size Tony Finch
- Re: [Doh] DNS Camel thoughts: TC and message size Hewitt, Rory
- Re: [Doh] DNS Camel thoughts: TC and message size Benno Overeinder
- Re: [Doh] [Ext] DNS Camel thoughts: TC and messag… Andrew Sullivan
- Re: [Doh] [Ext] DNS Camel thoughts: TC and messag… Andrew Sullivan
- Re: [Doh] [Ext] DNS Camel thoughts: TC and messag… George Michaelson
- Re: [Doh] [Ext] DNS Camel thoughts: TC and messag… Paul Hoffman
- Re: [Doh] [Ext] DNS Camel thoughts: TC and messag… Patrick McManus
- Re: [Doh] [Ext] DNS Camel thoughts: TC and messag… Tony Finch
- Re: [Doh] [Ext] DNS Camel thoughts: TC and messag… bert hubert
- Re: [Doh] [Ext] DNS Camel thoughts: TC and messag… Paul Hoffman
- Re: [Doh] [Ext] DNS Camel thoughts: TC and messag… Martin J. Dürst
- Re: [Doh] [Ext] DNS Camel thoughts: TC and messag… Patrick McManus
- Re: [Doh] [Ext] DNS Camel thoughts: TC and messag… Paul Hoffman
- Re: [Doh] [Ext] DNS Camel thoughts: TC and messag… Tony Finch
- Re: [Doh] [Ext] DNS Camel thoughts: TC and messag… Dave Lawrence
- Re: [Doh] [Ext] DNS Camel thoughts: TC and messag… Dave Lawrence
- Re: [Doh] [Ext] DNS Camel thoughts: TC and messag… Patrick McManus
- Re: [Doh] [Ext] DNS Camel thoughts: TC and messag… Ray Bellis
- Re: [Doh] [Ext] DNS Camel thoughts: TC and messag… Ray Bellis
- Re: [Doh] [Ext] DNS Camel thoughts: TC and messag… bert hubert
- Re: [Doh] [Ext] DNS Camel thoughts: TC and messag… Andrew Sullivan
- Re: [Doh] [Ext] DNS Camel thoughts: TC and messag… Dave Lawrence
- Re: [Doh] [Ext] DNS Camel thoughts: TC and messag… Dave Lawrence
- Re: [Doh] [Ext] DNS Camel thoughts: TC and messag… Robert Edmonds
- Re: [Doh] [Ext] DNS Camel thoughts: TC and messag… Dave Lawrence
- Re: [Doh] [Ext] DNS Camel thoughts: TC and messag… Dave Lawrence
- Re: [Doh] [Ext] DNS Camel thoughts: TC and messag… Mateusz Jończyk
- [Doh] AXFR as several messages Re: [Ext] DNS Came… bert hubert
- Re: [Doh] [Ext] DNS Camel thoughts: TC and messag… John Dickinson
- Re: [Doh] [Ext] DNS Camel thoughts: TC and messag… Ray Bellis
- Re: [Doh] [Ext] DNS Camel thoughts: TC and messag… Mukund Sivaraman
- Re: [Doh] [Ext] DNS Camel thoughts: TC and messag… Mukund Sivaraman
- Re: [Doh] [Ext] DNS Camel thoughts: TC and messag… Patrick McManus
- Re: [Doh] [Ext] DNS Camel thoughts: TC and messag… Tony Finch
- Re: [Doh] [Ext] DNS Camel thoughts: TC and messag… Martin Thomson
- Re: [Doh] [Ext] DNS Camel thoughts: TC and messag… Mark Nottingham
- [Doh] DNS Camel thoughts: TC and message size Patrick McManus
- Re: [Doh] [Ext] DNS Camel thoughts: TC and messag… Ólafur Guðmundsson
- [Doh] Are we missing an architecture? (was Re: DN… Andrew Sullivan
- Re: [Doh] [Ext] DNS Camel thoughts: TC and messag… Dave Lawrence
- Re: [Doh] [Ext] DNS Camel thoughts: TC and messag… Andrew Sullivan
- Re: [Doh] [Ext] DNS Camel thoughts: TC and messag… bert hubert
- Re: [Doh] [Ext] DNS Camel thoughts: TC and messag… Dave Lawrence
- Re: [Doh] [Ext] DNS Camel thoughts: TC and messag… Patrick McManus
- Re: [Doh] Are we missing an architecture? (was Re… Mark Nottingham
- Re: [Doh] [Ext] DNS Camel thoughts: TC and messag… Mukund Sivaraman
- Re: [Doh] [Ext] DNS Camel thoughts: TC and messag… Dave Lawrence
- Re: [Doh] Are we missing an architecture? (was Re… Andrew Sullivan
- Re: [Doh] [Ext] DNS Camel thoughts: TC and messag… Andrew Sullivan
- Re: [Doh] [Ext] DNS Camel thoughts: TC and messag… Patrick McManus
- Re: [Doh] [Ext] DNS Camel thoughts: TC and messag… Andrew Sullivan
- Re: [Doh] [Ext] DNS Camel thoughts: TC and messag… Patrick McManus
- Re: [Doh] [Ext] DNS Camel thoughts: TC and messag… Dave Lawrence
- Re: [Doh] Are we missing an architecture? (was Re… Dave Lawrence
- Re: [Doh] Are we missing an architecture? (was Re… bert hubert
- Re: [Doh] Are we missing an architecture? (was Re… Dave Lawrence
- Re: [Doh] [Ext] Are we missing an architecture? (… Ray Bellis