Which timeouts are used by BIND when resolving recursive queries?

Alberto Colosi alcol at hotmail.com
Fri Oct 5 15:12:42 UTC 2018


RFC say all

read RFC


BIND is a DNS system not an alien so follow RFC


Go and read RFC



________________________________
From: bind-users <bind-users-bounces at lists.isc.org> on behalf of ip admin via bind-users <bind-users at lists.isc.org>
Sent: Friday, October 5, 2018 4:13 PM
To: bind-users at lists.isc.org
Subject: Which timeouts are used by BIND when resolving recursive queries?

Hi,

 I understand that I can configure a global timeout for resolving recursive queries (resolver-query-timeout) but find that I cannot configure the timeout for an individual query used during DNS resolution.

 For testing I configured one unreachable forwarder (and enabled forward only) and saw (tcpdump) that BIND (9.10.6-P1) is first trying two queries with EDNS which each seems to have a timeout of 1.2s. Afterwards queries without ENDS are sent which seem to have a timeout of 1.6s, then 3.2s, then 6.4s, then 9s, finally the maximum (=total) resolver-query-timeout of 30s is reached.

 Is the timeout behaviour documented anywhere (similar to a stub resolver or dig, i.e. how long are timeouts, how many tries per server etc).

 If someone did find a logging setting that shows which servers are used when recursing (forwarding or delegations) to find a response (and when the individual queries time out) that would be helpful as well.

Regards
 Tom

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