Re: [Doh] [Ext] DNS Camel thoughts: TC and message size

Tony Finch <dot@dotat.at> Fri, 08 June 2018 13:27 UTC

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Date: Fri, 8 Jun 2018 14:26:53 +0100
From: Tony Finch <dot@dotat.at>
To: Mukund Sivaraman <muks@mukund.org>
cc: Robert Edmonds <edmonds@mycre.ws>, DoH WG <doh@ietf.org>, Dave Lawrence <tale@dd.org>
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Subject: Re: [Doh] [Ext] DNS Camel thoughts: TC and message size
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Mukund Sivaraman <muks@mukund.org>; wrote:
>
> I think BIND will happily load, zone transfer (in and out) and store an
> RRset in memory that didn't fit in 64kB. Initially for catalog zones,
> we'd have used such an RRset as there's no 64kB transfer limit to an
> RRset. However, anything over 64kB cannot be queried for as the server
> will fail to construct a reply.

BIND handles this better than I feared it might :-) See first dig output
below - you can axfr the zone if you want. However other implementations
did not have as much foresight - the second dig output is from a name
server hosted on the CommunityDNS anycast service - it seems to have
transfered the zone OK, though.


1. BIND

; <<>> DiG 9.13.0 <<>> +tcp +norec 65536.dotat.at in txt @grey.dotat.at
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 52562
;; flags: qr aa tc; QUERY: 1, ANSWER: 0, AUTHORITY: 0, ADDITIONAL: 1

;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 4096
; COOKIE: e70d27f85d21dee83f06c6445b1a828aed3ce0f8f53f262d (good)
;; QUESTION SECTION:
;65536.dotat.at.                        IN      TXT

;; Query time: 0 msec
;; SERVER: 2001:630:212:110::d:7a7#53(2001:630:212:110::d:7a7)
;; WHEN: Fri Jun 08 14:20:10 BST 2018
;; MSG SIZE  rcvd: 71


2. CommunityDNS

;; Warning: Message parser reports malformed message packet.

; <<>> DiG 9.13.0 <<>> +tcp +norec 65536.dotat.at in txt @ns3.gratisdns.dk
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 52381
;; flags: qr aa; QUERY: 1, ANSWER: 1, AUTHORITY: 0, ADDITIONAL: 1
;; WARNING: Message has 2571 extra bytes at end

;; QUESTION SECTION:
;65536.dotat.at.                        IN      TXT

;; Query time: 24 msec
;; SERVER: 2001:678:5::6#53(2001:678:5::6)
;; WHEN: Fri Jun 08 14:21:10 BST 2018
;; MSG SIZE  rcvd: 2615


Tony.
-- 
f.anthony.n.finch  <dot@dotat.at>;  http://dotat.at/
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