What are the DNS Query Timeouts and Retries for Resolvers

Question

Is there a standard, or common practice, on the timeouts and retries settings for resolver when is performing recursive query for a domain?

A description of the problem you're trying to solve would probably garner more useful answers.

voretaq7 · Answer 1 · 2011-07-22 17:22:08Z

up vote 0 down vote

"Whatever the administrator sets them to be (within reason)" -- On a unix box these are configured in /etc/resolv.conf

The defaults (from /usr/include/resolv.h on FreeBSD 8) are:

RES_TIMEOUT = 5 seconds (Max 30sec when configured from resolv.conf)
RES_DFLRETRY = 2 retries (Max 5 retries).

Quoth the manpage in regard to timeouts:

 The resolver may wait longer during subsequent retries of the current query
 since an exponential back-off is applied to the timeout value.

See the resolv.conf manpage for more information

answered Jul 22 '11 at 17:22

voretaq7♦
34.4k33281

	Strictly speaking, those are just the retry and timeout values for the DNS client library as it is talking to the resolving proxy DNS server. The timeouts and retry strategies used by that server itself, in its back end, are not configured there. – JdeBP Jul 23 '11 at 0:26
	@JdeBP - that's correct: The question above appears to be asking about the resolver library (as opposed to the DNS server). A similar option is available for BIND itself in `named.conf` (min-retry-time & max-retry-time), as well as other configurable timeouts, however as you mentioned those are not configurable from the client's end. – voretaq7♦ Jul 24 '11 at 5:13
	You have your DNS terminology wrong. Read your RFCs, in particular RFC 1034 §2.3 and §5.3. If the questioner is asking about "the resolver", then xe is asking about the entire resolution mechanism including the proxy DNS server that the DNS client talks to. That is what "the resolver" properly is. This is why I and others use clearer terminology such as "DNS client library". – JdeBP Jul 25 '11 at 9:54
	The question was specific to the DNS resolvers, or the DNS servers handling the resolution for the clients - and not the client (OS) itself. – GeorgeU Jul 25 '11 at 13:22

feedback

1 Answer