Concurrent Connection Issue / Download Accelerator?

[jblim]

Sorry if this is in the wrong category, I wasn't sure where to put it.

I have been having issues with images and tables not loading correctly on my website. Others can't seem to reproduce the issue, but it is still critical for me to sort out because I can't test my site and see changes that I make. I have cleared cache, reinstalled browsers, etc. and am still getting the issue.

My host, Dreamhost, told me it has to do with me exceeding my concurrent connection limit and that it might be caused by a download accelerator. Anyone know how I can troubleshoot this and fix the problem??? Here is their message...

You're still hitting that limit:

[Wed Jun 17 17:07:52 2009] [error] [client x.x.x.x] access to
/wp-content/uploads/satisfaction-guaranteed-150x150.jpg failed for 76.94
.174.189, reason: Client exceeded concurrent connection limit of 20,
referer: xxxx.html

We have this in place as a protection against DDOS attacks. Usually,
this is caused by download accelerators. When attempting to load your
site, I get 20 some odd connections alone. If your computer isn't closing
those connections for whatever reason, you'll be locked out, and get the
error I pasted above.

Unfortunately, we cannot turn that off, so you'll need to figure out why
it's happening for your computer. I checked your logs, and it's not
happening for any other IP addresses accessing your site.

[phper]

Do you have any download accelerators on your PC?

I don't think that this post would be for the PHP category anyway.

Sorry

Alex

[Atli]

Hi.

What OS, browser, download acceleration software, etc... are you using?

Somehow, as I read your description I immediately though "the router", but it could just as well be your network card, your OS or your browser.

To rule out your OS and browser, try booting a Linux live-cd and see if you can view your site in the browser that comes with it.
(Ubuntu is good... Comes with Firefox :)).

If that turns out to show the same problem, it might be that your network hardware is broken, or that a router (or such) is not working properly.

[jblim]

Thanks guys. I tested in Firefox, Safari, Opera and IE and same issue in all. So I reset the modem and disconnected the router, plugging directly into my modem. The issue went away, but I need to plug the wireless router back in now to test if the issue is with the router or if the modem just needed to be reset.

Anyway, I spent a week going through code and a bunch of other things trying to figure this out. I wish I would have posted here earlier and got feedback that the router or modem could be the issue.

Thanks!

[jblim]

Here is the strange thing that I still can't figure out...

If I take the Netgear wireless router out and connect directly to my modem, everything loads fine. As soon as I use the wireless router, my site gets DDOS attacks and images/frames don't load correctly.

So, it would seem that the router is the problem, right? But when using the router, my site is the ONLY site that has loading issues. This makes me think my site is the problem. So which is it? The router, my site or both?

Any thoughts on what could be causing this or how to trouble shoot? I have tested in all browsers - same thing.

Thanks!

[Atli]

It certainly sounds like your router is the problem, although I agree it is odd that it targets a single site.

Have you done any sort of port forwarding or added any sort of firewall rules to your router specifically towards your site?
Maybe there is a way to just wipe it clean. A sort of "reset to factory settings" thing?

There is one thing you could try on your website.
Adding the header('Connection', 'close'); header to it should instruct the sever, and the client, to close the connection as soon as the transaction is done, rather than wait for a while to see if there is more coming.

It shouldn't affect your site, but it would be interesting to see if this has any effect on this issue.