Delay following DNS response:

Posted on 2006-05-09
Last Modified: 2013-12-07
I've been using Ethereal to help narrow this annoying problem down.  Here's what I have.

I have been annoyed that my home page (google) takes longer to load than I wouild expect.  I realized it was actually an issue when my girlfriend's machine was consistently NOT having this problem, whereas mine WAS.  Well it turns out that the packet capture shows a DNS query to the router, immediately followed by a response with the resolved name.  However, then there is abouit a 7 second delay before the next packet goes out.

In order to eliminate the browser as being the issue, I repeated this test using PING.  Here are the results (pretty much the same as when bringing up the main google web page):

No.     Time        Source                Destination           Protocol Info
      8 0.730549           DNS      Standard query A WWW.GOOGLE.COM
      9 0.743367          DNS      Standard query response CNAME www.l.GOOGLE.COM A A
     22 7.757377        ICMP     Echo (ping) request
     23 7.770849         ICMP     Echo (ping) reply
     24 8.770850        ICMP     Echo (ping) request
     25 8.798386         ICMP     Echo (ping) reply
     26 9.770852        ICMP     Echo (ping) request
     27 9.796171         ICMP     Echo (ping) reply

Aside from me, the printer, and the Tivo, the network is pretty quiet.  The above capture is filtered, but as you can see from the first column (packet number), what I pasted here is a third of the total packets.  

I am using DHCP both for IP and DNS, so since the other machine is not having this lag issue, I suspect it is with my own.

I don't suspect any wireless radio issues, since in such a case I would expect sluggishness all the time together with packet errors.  I do have an "excellent" wifi signal power reading, as far as that goes.

Earlier in the day, I thought I traced the problem to some "" software which was still hanging aroiund from Adelphia cable (since I saw their server being used almost like a proxy in the packet capture).  I have removed the software, there are no more requests to their server, but I still have this time lag.

Thanks in advance to anyone who can help fix this annoying issue.
Question by:mrdtn
    LVL 10

    Expert Comment

    I know you say they are both running DHCP for IP and DNS, but have you confirmed that the two machines are in fact using the same DNS server?
    LVL 6

    Author Comment

    Yes.  They are both using the router as the DNS, which in turn is using some Verizon FIOS DNS at 78.??.??.??.  I did a packet capture using the other machine.  I would run it again and post it right now, but it is currently being used.

    LVL 6

    Author Comment


    I guess I'm going to answer my own question.  I am going to request that it be closed but not deleted, since the information here will still benefit the community.

    After further troubleshooting, the thing that fixed this problem was disabling Internet Connection Sharing (ICS).  I'm not even sure why it was enabled.  I may have left it enabled when I was using ICS to allow a Wifi enabled PDA connect to the net via an ad-hoc connection to my laptop.  I thought I had disabled it when I was done using it for that purpose, but I guess not.  I disabled it and no more delay.  Problem fixed.

    If any other networking expert can provide more of an explanation as to what may have been going on here, it would be helpful.  I fix a lot of problems, but I hate it when I don't know all the reasons why a particular solution fixed a particular problem.  All I can ascertain is that ICS is doing a lot of pre-emptive timed waits or something.



    Accepted Solution

    Closed, 250 points refunded.
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