truncated responses vs. minimal-responses?

Tony Finch dot at dotat.at
Wed Nov 28 18:38:08 UTC 2012


Matus UHLAR - fantomas <uhlar at fantomas.sk> wrote:
>
> I know. But there are cases you just have much of data in the DNS and what I
> am asking is, if BIND really does skip authority section, if it helps to
> avoid sending truncated packets.

Yes it does. For example, have a look at responses to queries for dotat.at
in mx for various buffer sizes and observe that RRsets are dropped but the
TC bit is not set.

; <<>> DiG 9.9.2-vjs287.12 <<>> +norec +dnssec +ignore +multiline mx dotat.at @puck.nether.net
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 31890
;; flags: qr aa; QUERY: 1, ANSWER: 2, AUTHORITY: 5, ADDITIONAL: 7

;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags: do; udp: 4096
;; QUESTION SECTION:
;dotat.at.              IN MX

;; ANSWER SECTION:
dotat.at.               3600 IN MX 1 mx.cam.ac.uk.
dotat.at.               3600 IN RRSIG MX 5 2 3600 (
                                20121217120814 20121117113945 56700 dotat.at.
                                FLOLFiTEbnAsBka05qJK9nbY3sknNIbG2zSewoqIUkI1
                                fnm8PDzOB42WoAI2N4vNcQQVkd560B8hRB5a0+tLLZOB
                                +lz7EA1uLnqCaINJ46BOA0+hXAcAMZMbzYFfVOTN8T/K
                                89WkExApwdXxffi2dSGOKXAj4KuM3ryfz1g/n7g= )

;; AUTHORITY SECTION:
dotat.at.               3600 IN NS black.dotat.at.
dotat.at.               3600 IN NS ns1.gratisdns.dk.
dotat.at.               3600 IN NS ns3.gratisdns.dk.
dotat.at.               3600 IN NS puck.nether.net.
dotat.at.               3600 IN RRSIG NS 5 2 3600 (
                                20121225040504 20121125035952 56700 dotat.at.
                                Hdvs1a2cdGOezLYbNTr1T47g+ZYA9ceBgUQD1tkHvJjL
                                0+nwREF/0JRs9Neb/Y+jpe0+PeIcDKCEOyD8GTeyc0ve
                                Ez4sKt3OmkVUp1QN4gFmaeH/oPnPmhYzIuSrlgLkDwOl
                                IoiixyHNKdF1Op14uUOS8bG3Qn8/HrHS3VjvogM= )

;; ADDITIONAL SECTION:
puck.nether.net.        86400 IN A 204.42.254.5
puck.nether.net.        86400 IN AAAA 2001:418:3f4::5
black.dotat.at.         3600 IN A 131.111.11.130
black.dotat.at.         3600 IN AAAA 2001:630:212:100:646f:7461:742e:6174
black.dotat.at.         3600 IN RRSIG A 5 3 3600 (
                                20121217151010 20121117143125 56700 dotat.at.
                                ASD2mv5bJgCvope4pfPMxG9LULCOgnUEgRfpw6BIYaRi
                                1wGMbezO2L7e9PVPeZ6vN5Cc0T+faN5NpgT0o9aJTdSK
                                vRoFABIyNsPAMS41ekPL6KdAoz5vbHvplDaNBIfIXs+B
                                NMySjVw+K/kDFjdW2ygPaRQb8WzfCQoCUEuUc7Y= )
black.dotat.at.         3600 IN RRSIG AAAA 5 3 3600 (
                                20121224154647 20121124151930 56700 dotat.at.
                                sb5EcG/+C8PG4E5BFUVag59M9zDDwxZGAFdgnMHSacVX
                                2kBPoLx+O7IwyO/wanYFpW/sINojumV0NVvE48AI2Ubs
                                5R/YKIKwHOwgrbwXB2S86x9xGUIGljMJtN07NxbGGpKS
                                CDhlGH7za4Au32srZFVNu3cozq0Q20dsWKHQ3DA= )

;; Query time: 93 msec
;; SERVER: 2001:418:3f4::5#53(2001:418:3f4::5)
;; WHEN: Wed Nov 28 18:33:16 2012
;; MSG SIZE  rcvd: 922


; <<>> DiG 9.9.2-vjs287.12 <<>> +norec +dnssec +bufsize=512 +ignore +multiline mx dotat.at @puck.nether.net
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 46694
;; flags: qr aa; QUERY: 1, ANSWER: 2, AUTHORITY: 0, ADDITIONAL: 1

;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags: do; udp: 4096
;; QUESTION SECTION:
;dotat.at.              IN MX

;; ANSWER SECTION:
dotat.at.               3600 IN MX 1 mx.cam.ac.uk.
dotat.at.               3600 IN RRSIG MX 5 2 3600 (
                                20121217120814 20121117113945 56700 dotat.at.
                                FLOLFiTEbnAsBka05qJK9nbY3sknNIbG2zSewoqIUkI1
                                fnm8PDzOB42WoAI2N4vNcQQVkd560B8hRB5a0+tLLZOB
                                +lz7EA1uLnqCaINJ46BOA0+hXAcAMZMbzYFfVOTN8T/K
                                89WkExApwdXxffi2dSGOKXAj4KuM3ryfz1g/n7g= )

;; Query time: 98 msec
;; SERVER: 2001:418:3f4::5#53(2001:418:3f4::5)
;; WHEN: Wed Nov 28 18:35:32 2012
;; MSG SIZE  rcvd: 233


Tony.
-- 
f.anthony.n.finch  <dot at dotat.at>  http://dotat.at/
Forties, Cromarty: East, veering southeast, 4 or 5, occasionally 6 at first.
Rough, becoming slight or moderate. Showers, rain at first. Moderate or good,
occasionally poor at first.



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