things seem slow

Simon Waters Simon at wretched.demon.co.uk
Sun Jan 19 19:17:46 UTC 2003


-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1

T wrote:
> I was wondering if anyone might have some insight as to
> why it seems like there is too long of a delay for names to
> be looked up on my LAN?
>
> If I ping a name on my LAN it takes
> rtt min/avg/max/mdev = 0.220/0.224/0.233/0.013 ms

Okay my painfully slow encrypted wireless LAN gives 2.4/2.5/2.7
ms, so ten times slower(ish).

> if I dig the same name it takes Query time: 323 msec
>
> does this seem ok? I copied the results as they were printed
> after executing the commands.

I get about 6 to 12 ms on said LAN, so 50 times faster.

> Nsswitch has \x{201C}files dns\x{201D} only but it did not
speed anything up.

Okay dig won't use this AFAIK, it goes straight to
/etc/resolv.conf where it hopefully finds the IP address (not
name!) of the nameserver to query on a nameserver entry.

i.e
cat /etc/resolv.conf
search eighth-layer.internal
nameserver 192.168.0.1

(what my personal wireless network only has one recursive DNS
server tsck tsck - but you can go overboard for a primarily two
user network ;-)

> Am i missing something?

Silly question - are these queries succeeding?

Dig expects fully qualified names (by default) so I'm doing;

dig hostname.eighth-layer.internal

If I "dig hostname" the query fails, but only after asking the
root servers, so that takes 400ms or there abouts. If I repeat
"dig hostname" the negative answer is cached and the query is
down to 6 to 12ms again. ("dig +search hostname" works quickly
here, but I imagine an incorrect search directive or other error
in resolv.conf could slow that down to 400ms as well).

Does the same query take as long if you repeat it?

Is the DNS servers running out of memory? Although you can do
quite a bit of paging in 400ms :-(

What is in /etc/resolv.conf ?
-----BEGIN PGP SIGNATURE-----
Version: GnuPG v1.2.1 (GNU/Linux)
Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org

iD8DBQE+KvnWGFXfHI9FVgYRArB6AJ42LFgq4EmGDQ19NK63w8vTljDIdgCfZ+2d
G+fQjK7+Fa4e9EYyWuCIqbw=
=2LWW
-----END PGP SIGNATURE-----



More information about the bind-users mailing list