I've written Zack directly, but wanted to add a couple observations
since sharing one's ignorance in public is a great way to learn :-)
>> (2) Can you isolate the problem to the local DNR (Domain Name
>> Resolver)
>
>They both are taking about 6-15 seconds today. I may have used NS
>Query incorrectly,
It looks like you entered an invalid query. Type "A" is for finding the
IP address for a given domain name. To lookup the name for an IP
address, you would use query type "PTR".
It's not surprising it took about 6 seconds for the request to fail.
What we really want to test is whether talking to the Name Server
directly is consistently quick even when the DNR is slow.
>tcpdump://en0@localhost;options=-n -p udp port 53
>11:23:34.523781 IP 192.168.0.50.50424 > 205.171.3.65.53: 39700+ A?
>hotmail.com. (29)
>11:23:42.025238 IP 192.168.0.50.50427 > 205.171.2.65.53: 39700+ A?
>hotmail.com. (29)
>11:23:42.112253 IP 205.171.2.65.53 > 192.168.0.50.50427: 39700 2/0/0
>A 64.4.33.7, (61)
>----------------[End of response]----------------
>
>The 11:23:34.523781 line appears instantly, then an 8 second delay
>until the 11:23:42.025238 line appears, then 11:23:42.112253 is
>instant after that. I don't quite know if I am reading this right
>but, doesn't it look like the first query never comes back, so it
>times out and tries sending it again, at which point it gets a
>response back immediately?
Yes, but notice the second try is sent to a different name server:
205.171.2.65 versus 205.171.3.65
If the primary server is overloaded or unreliable, that might explain it.
>Could I shorten that timeout to say half a second?
Unfortunately the DNR timeout values are hardwired so not easily tuned.
By way of general observation, the DNR timeout behavior in Tiger seems a
little odd. It should retry the first server after 1.5 seconds and go
on to an alternate server at around 3 seconds. At 6-7 seconds it should
give up reporting there was no response. I don't know why or if Apple
intentionally changed this common DNR behavior.
- Peter
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