[79987] in North American Network Operators' Group
Re: Slashdot: Providers Ignoring DNS TTL?
daemon@ATHENA.MIT.EDU (Crist Clark)
Tue Apr 19 17:33:58 2005
Date: Tue, 19 Apr 2005 14:30:40 -0700
From: Crist Clark <crist.clark@globalstar.com>
In-reply-to: <20050419.084745.5555.402725@webmail25.lax.untd.com>
To: nanog@merit.edu
Reply-To: crist.clark@globalstar.com
Errors-To: owner-nanog@merit.edu
Fergie (Paul Ferguson) wrote:
>
> Interesting thread on /. --
>
> http://ask.slashdot.org/article.pl?sid=05/04/18/198259&tid=95&tid=128&tid=4
FWIW, I did some 'dig'ing on my Comcast home service. The DHCP is handing
out 204.127.198.4 and 63.240.76.4 for DNS at the moment.
I ran a query for a name in a zone I control that has a five minute TTL
on 204.127.198.4. The first query came up with 5 minutes. I quickly made
a change to the zone. hirty seconds after the initial query, I try again...
err... and come up with the change. Hmm... Not caching at all? Another
30 seconds and I get the change, with 5m TTL. Thirty seconds later, I
get the original response with appropriately decremented TTL. Another
thirty seconds, I get the change, with 4m TTL.
My findings: Comcast is now using some kind of load balancing that messes
with this kind of testing. 204.127.198.4 is not a single resolver. However,
as far as I could tell, they were obeying the TTL. After 5 minutes, all
of the responses were coming back with the change. The TTL values in the
responses were decrementing as expected.
--
Crist J. Clark crist.clark@globalstar.com
Globalstar Communications (408) 933-4387
