HTTP very slow

  Zigor 14:55 02 Jan 08


I have a home network with two computers connecteded to a wifi router (password protected and encrypted). Last week one of the computer connections crashed with no apparent reason.

After running an antivirus and antispyware with no success in solving the problem I formatted and reinstalled Windows XP Pro SP2. The problem is that the wifi card does not work and I now use an ethernet cable to the router. But:
-HTTP is very slow (both in IE7 and Firefox 2)
-Ping to router and internet sites is fast
-Other protocols work well: ftp, p2p, ...
-Web browsing in the other computer is also working perfectly.

Any advice about which steps to follow?


  silverous 15:08 02 Jan 08

A few things to consider:

i) Which ISP are you with? I know a colleague has had web performance issues with TalkTalk until he changed his MTU setting on each PC/laptop.
ii) Is there a 'cache' set in internet explorer ? If it is a fresh XP install (unless it is some manufacturer specific disk) then I can't imagine so but worth asking.
iii) If you do ipconfig /all from a command prompt on both are you seeing same DNS servers listed? I'm guessing DNS is not an issue as you are saying that pinging internet sites (presumably by name) is fast.

Just some ideas.

  silverous 15:09 02 Jan 08

Sorry - for (ii) I mean a proxy server. If you are not familiar, check Tools, Internet Options, Connections, Lan Settings and let us know what's in there.

  Zigor 15:36 02 Jan 08

i) I am from Spain. ISP is Telefonica. About MTU setting, I think the computer with no problems has the default MTU. In the 'problematic' one, I also run TCP Optimizer with no apparent benefits.
ii) I am not 100% sure about this, but I think it has no proxy server because if so, the other computer would also experience the same problems.
iii) Same DNS servers and not an issue because the pings were made by name.

Is it possible that any malware/trojan/spyware has survived the formatting (as I have other hard disks in the same computer) and is now again affecting the http connections?

  silverous 16:04 02 Jan 08

RE: (ii) the proxy server is a setting in internet explorer and is sometimes set to an ISP's cache servers so it would be a per-machine thing, so the fact that the other machine is ok doesn't mean it doesn't have one. Worth checking (see my post @ 15:09 for how if you don't know).

I suppose it is theoretically possible if the malware/trojan/spyware was present in a file on the other drives and you re-ran that file it might re-infect however: i) You don't know for sure you had any of those things as your scans didn't highlight them and ii) Such things have to be executed by something, formatting and re-installing means your operating system startup, boot sectors etc. should all be clean (unless as above you've executed something off the other drives that has re-infected). I'm not convinced this is malware related.

The good thing is you have another machine to compare which takes a whole series of issues (like something happening at your ISP) out of the equation.

Also good that you have both firefox and IE as the fact they are both slow suggests it isn't a problem with specific browser.

This is perhaps worth a try (borrowed from click here):

Start > Run > type in cmd > OK to get a Command window

At the flashing cursor type cd\ Enter to change to the C:\ root

At the C prompt type ipconfig /flushdns Enter.

Then exit the command window.

Try again then. I'm struggling otherwise, unless it is something wrong with the windows tcp/ip stack to do with HTTP only..... something along these lines may help but it sounds relatively drastic (resetting TCP/IP stack):

click here

  Dipso 17:05 02 Jan 08

You may have already investigated this but...I had this issue and in my case it was my software firewall Zonealarm which was causing it, do you have a sw firewall?

  silverous 09:31 03 Jan 08

Also, having thought about this some it possible that ping "appears" fast but is actually a very simple single packet request (I'm guessing a little here) so you don't notice any problem whereas http is obviously a more intense set of network traffic - could there be a fundamental (physical) connection issue e.g. your network card, cable, router port etc.? Have those all been eliminated?

e.g. the negotation on the network card may be set to half/full duplex rather than auto negotation, that kind of thing? Cable may be faulty (have you tried another?).

Just some things to eliminate, I don't have a strong feeling that any one of them is the real problem.

  Zigor 10:43 03 Jan 08


Yesterday when I arrived home I tried the flushdns with no success. About the other suggestions, I have tried the same web page with the other computer and goes fast while in the "faulty" one it is very slow.

Another weird thing I tried yesterday was changing the local ip address of the computer from to and suddenly for a while web surfing was again fast, but it only lasted for about 15 minutes. It is as if "the bug" did not detect this new ip and so did not slow the connection and after around 15 minutes it detected and was again slow.

The config of the router before this problem started was:
-No dhcp
-Router ip (gateway)
-Computer 1 (the faulty) with a wifi card
-Computer 2 with a wifi card

When problems started and apparently the wifi card of computer 1 was faulty, I disconnected it and enabled the ethernet port assigning ip

In the router, I have no specific rules for appart from virtual servers for p2p ports.

I have qos enabled with http priority high but with no specific ip address.

  silverous 13:19 03 Jan 08

I don't think you've answered my query re: the network card/cabling?

Another possibility: could something be running in the background soaking up your cpu/network bandwidth from the Computer 1 ?

To a degree I'd expect that would slow down Computer 2 also but not to the same extent as it would Computer 1.

I wonder if it is worth downloading a packet tracing / TCP/IP monitoring / HTTP debugging tool to see if you can identify what is happening under the hood?

e.g. (one or more of) :

click here

click here

click here

Could it be that windows downloads are set to automatic and that is downloading lots of updates at the same time? The 15 minute thing is interesting.

  Zigor 13:41 03 Jan 08


Thank you very much for your prompt replies. I will try the network card/cabling tonight. I have an spare cable, so I can try it and also can connect the other computer with the cable so it will be easy for me to discard cable problems. But I am not sure about network card, I could have an spare one but I will have to check. Is there a network card testing soft?
About background processes, I have automatic updates disabled and my system is updated so it cannot be that thing. And also, after those more or less 15 minutes, I turned off the computer and when loggin again, http was slow from the beginning.
About the tools you suggested, I will try them tonight too.

  silverous 14:18 03 Jan 08

Great, I'm keen to get to the bottom of this one as it is a challenge.

I think the tools might be useful, and possibly the comparison of the tools running on both machines so you can compare.

I'm not aware of any generic network card testing software however the manufacturer/supplier of the card/PC may supply some diagnostics.

As well as flushdns, did you look through the other Microsoft network diagnostics information ? You can reset the TCP/IP stack and other aspects by following that.

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