FYI: Mac OS X, Safari (et al), and DNS timeouts
shobson0309 at colony.com
Wed Dec 22 14:10:32 UTC 2004
Just an FYI which I hope might be of help to someone else.
A couple of weeks ago I set up an internal DNS server (BIND on a
Linux box) on my little home network, and then I started getting
"this site could not be reached" type errors from Safari - you know,
the ones where it almost always works second time around. After a bit
of packet sniffing, and googling it seems that this is a known
problem engineered into OS X by Apple !
From observation, when I go to a website, the Mac does (up to) five
DNS queries, at one second intervals, and with a one second timeout.
Naturally, some resolutions can take longer than 6 seconds to
complete and so the user gets many failures - always succeed second
time around. Thanks a lot Apple !
I found messages on various forums about how switching to using ISPs
nameservers cured it, and then someone pointed out that in fact the
real reason for these 'successes' was that by listing two
nameservers, the timeout got doubled ! Listing my own server twice in
the DHCP config cured the problem.
I also saw comments about version Mac OS 10.3.7 including a new
lookup tool (not just DNS) which will have some configurability.
NOTE: This is a throw-away email address which will reach me for as
long as it stays spam-free, remove date for real address.
Simon Hobson MA MIEE, Technology Specialist
Colony Gift Corporation Limited
Lindal in Furness, Ulverston, Cumbria, LA12 0LD
Tel 01229 461100, Fax 01229 461101
Registered in England No. 1499611
Regd. Office : 100 New Bridge Street, London, EC4V 6JA.
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