[Cialug] Inconsistent consistently long DNS lookup times

[bofh at visi.com]

FYI, this issue (specifically with Qwest DNS servers) also 
has been raised in the Twin Cities over the past month.  
It seems to be spotty though, even amongst those 
experiencing issues.  What's interesting is that the 
Google DNS servers seem to have worked for them at the 
time.  No one--to my knowledge--has discovered a root 
cause.  Misconfiguration? Cyberwarfare? Time to upgrade 
<insert whatever> due to increased usage?  Eh.  All asked 
and none answered.

As for WinXP, IIRC it has a DNS cache.  Might want to 
clear that (via ipconfig?).


On Sun, 7 Mar 2010 22:42:15 -0600
  Colin Burnett <cmlburnett at gmail.com> wrote:
> This issue is kind of hairy.  HTTP in Firefox and 
>Seamonkey; FTP via ncftp; and NTP via ntpdate all experience a 6-second lag 
>if I use a domain name, but do not experience a lag if I use an IP. 
> My Python-based Amazon web service app also experiences 
>this lag (which increased it's run time from about 15 min to over an 
>hour).  However, if I use links or links2 I get no lag for both domain 
>name and IP.
> 
> Pulling out the strace I see this in every app (that's 
>easily strace'd) where there is lag:
> 
> socket(PF_INET, SOCK_DGRAM|SOCK_NONBLOCK, IPPROTO_IP) = 
>3
> connect(3, {sa_family=AF_INET, sin_port=htons(53),
> sin_addr=inet_addr("205.171.3.65")}, 28) = 0
> gettimeofday({1268021564, 84586}, NULL) = 0
> poll([{fd=3, events=POLLOUT}], 1, 0)    = 1 ([{fd=3, 
>revents=POLLOUT}])
> sendto(3, 
>"\301\371\1\0\0\1\0\0\0\0\0\0\3www\6google\3com\0\0\1\0\1",
> 32, MSG_NOSIGNAL, NULL, 0) = 32
> poll([{fd=3, events=POLLIN|POLLOUT}], 1, 5000) = 1 
>([{fd=3, revents=POLLOUT}])
> sendto(3, 
>"\17\377\1\0\0\1\0\0\0\0\0\0\3www\6google\3com\0\0\34\0\1",
> 32, MSG_NOSIGNAL, NULL, 0) = 32
> gettimeofday({1268021564, 84811}, NULL) = 0
> poll([{fd=3, events=POLLIN}], 1, 4999)  = 1 ([{fd=3, 
>revents=POLLIN}])
> ioctl(3, FIONREAD, [148])               = 0
> recvfrom(3, 
>"\301\371\201\200\0\1\0\7\0\0\0\0\3www\6google\3com\0\0\1\0\1"...,
> 2048, 0, {sa_family=AF_INET, sin_port=htons(53),
> sin_addr=inet_addr("205.171.3.65")}, [16]) = 148
> gettimeofday({1268021564, 125360}, NULL) = 0
> poll([{fd=3, events=POLLIN}], 1, 4959)  = 0 (Timeout)
> 
> 
> The DNS server 205.171.3.65 is the IP address I get from 
>Qwest.  I've
> tried this with the secondary 205.171.2.65 as well as 
>the Google DNS
> of 8.8.8.8 and 8.8.4.4.  All experience a 5-6-ish second 
>delay before
> the poll() reaches its timeout (apparently 4959 ms in 
>this instance).
> All use UDP 53 to the same server.
> 
> Putting an strace -f on links yields a similar polling 
>of the same DNS
> server but it doesn't time out.  It seems to only take 
>about 1/4 ms to
> resolve though (would seem to indicate it's cached 
>somewhere).
> 
> 
> The problem is blatantly that the poll time's out when 
>doing a resolve
> and I don't know how the resolving differs between
>Firefox/Seamonkey/ntpdate/ncftp and ping/links/links2, 
>but it clearly
> is.
> 
> My setup is gentoo box behind an Actiontec (yippy!) 
>modem on a 7MB
> Qwest DSL connection.  Lookup performance on my Win XP 
>laptop would
> seem to indicate that it's not the internet connection 
>since Firefox
> on it has no problems.  This has been going on for a 
>couple weeks
> (yes, and I'm just now getting tired of it) and I do not 
>recall or
> know of any recent changes to anything.  I've done 
>random package
> updates including a jump from KDE 4.3.3 to 4.3.5, but 
>this happened
> before that.
> 
> Otherwise, I have little complaint internet-wise.
> 
> I would be happy to provide more information but I'm not 
>entirely
> should what is appropriate and I could easily flood this 
>with
> thousands of lines of strace.  :)  Where do I go from 
>here?!
> 
> 
> Colin Burnett
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