clearing local caches

[Dave Sparro]

Scott Haneda wrote:
> On Jul 15, 2009, at 12:29 PM, Dave Sparro wrote:
> 
>> Scott Haneda wrote:
>>> ... However, I would like to just get DNS response times.
>>>
>>> Perhaps take the list of hosts and feed them to a iterative script 
>>> calling dig, and fish out the response time?  This does add the 
>>> problem of redirects of course would not be followed, so I would have 
>>> to pre-fetch all my urls and follow them to get my testing list.
>>
>> I don't see how you could call the results from any other method "DNS 
>> response times."
>>
>> If you used a web browser to measure from, you'd be introducing all 
>> sorts of other latencies.   Delays from the web server itself.  The 
>> webserver may have to talk to a database to output the HTML.  The 
>> transfer of the actual HTML code isn't instantaneous. (ad that's just 
>> off the top of my head).
> 
> 
> Correct.  So I will end up pulling down the file, extracting the 
> hostnames, following any redirects, and extracting the resulting 
> hostnames.  This gives me a nice list of hostnames that I can run 
> through an iterative loop in dig.
> 
> I just need to make sure that I am not getting a locally cached result.  
> I suspect there is no way to force a non caches result from the remote 
> ended resolver?

If you aim your dig at a specific DNS server you'll be getting the 
results from that IP address.  There won't be  any local resolver 
involved.

If you aren't in control of the remote resolver, there's no way to 
predict the cache status of your query on the remote side.