Horrendous web slowdown when torrent client running

[tfboy]

I'm really confused with this I don't know where else to post this as I'm not sure if it's an OS issue, a PC hardware issue, a network issue, a broadband issue, etc.

I have a 20Mb NTL cable connection which works well.

When not running any internet-intensive applications, my web browsing is super speedy.

But, as soon as I launch a torrent client, my web browsing grinds to a halt.

"OK", I hear you say, "it's another of those bandwidth throttling problems". Well, yes and no

I have my NTL CM which goes to a Linksys WRT54G wireless router. From there, a single cable goes to an 8-port gigabit switch, which then serves the various PCs at home, including my desktop PC and my server in the attic.

If I launch the torrent client on my server up in the attic, my desktop PC carries on browsing the net at normal speeds - I have no slow down.

So, I doubt it's an NTL throttling, nor is it my modem's inability to manage the traffic efficiently - I can only put it down to my local NIC in my desktop PC which has troubles. But there's nothing strange about it Standard MSI P35 platinum running at stock speeds, and using a built-in Realtek 8168B gigabit ethernet NIC.

Interestingly, if I have the torrent client running on my desktop PC which then grinds to a halt, if I then close it, it still takes a good few minutes before normal network activity is resumed. During the slow down, I can't even access my router's configuration page.

Any ideas?

[TAKTAK]

have you setup port forward and things? and limited the torrent programs usage

[Jay]

maybe maximum connections in XP has been reached.

[Craig321]

Definitely a limit on your PC if it's only grinding to a halt on the PC that's torrenting.

Can't you set up your PC in the attic to do all your downloads? Control it through VNC and set up shared folders maybe.

[tfboy]

Yeah, that's what I now have - the server is doing all the stuff and stays on pretty much 24/7.

I was just curious.

My desktop is running 64 bit version of Vista with SP2.

I'll do some network sniffing one day and find out what's really going on

[Viper81]

As Jay says it's probably you hitting the maximum connections limit on the OS.
Next time you've got bittorrent running check your event logs for TCP/IP error messages.

[Blitzen]

Doesnt VM slow you down when using Torrents (as they are used for illegal purposes most of the time)

[Agent]

Doesnt VM slow you down when using Torrents (as they are used for illegal purposes most of the time)

No. Its a myth.
There is no packet shaping on VM.

[Rob_B]

Reduce your max upload speed. If I don't set it to under 20k I just can't browse at the same time (using Azureus)

[Lourdes]

If XP try increasing the TCP/IP connection thing with the various patchers.

[haku]

its usually not the download that chokes your total throughput its the upload most of the time on a ADSL line. I am assuming you have ~20meg downstream and ~1 meg upstream. You have to make sure your upstream can cope with the high volume of packets passing through your network not just your downstream. See if your upstream is being saturated. Try limiting your upstream usage from your torrent client and see if that makes any difference. If the upstream gets saturated then you can't get your HTTP GET or POST requests out of your network or even start the tcp handshake. If you sniff your network you'll see a lot TCP SYN packets but no matching SYN-ACK or even timeouts and retransmits, if your upstream is saturated i.e.
Ofcourse this is just speculation. Its very interesting that the torrent client running on the server doesn't affect the network in quite the same way though. does client on your desktop and server have the same config and same torrents downloading? Is it the same OS on both boxes?

Cheers.

[impossible]

Reduce your max upload speed. If I don't set it to under 20k I just can't browse at the same time (using Azureus)

I second that!

if you dont limit your upload then your ACK's dont have a chance to get back to the sites you are browsing.

Imp

[tfboy]

I'm nowhere near the limit of my upstream though! It's really strange.

Even if there's hardly any traffic, it still grinds the whole network connection to a halt.

I now have my server back up and running and it will happily seed at a throttled 80kB/s and the speed of my normal browsing on the desktop PC is hardly affected.

[Stigggeh]

Reduce your max upload speed. If I don't set it to under 20k I just can't browse at the same time (using Azureus)

This is usually the biggest cause of slowdown, people just leave the upload limit at 0 (which is unlimited)

[sleepyhead]

I'm really confused with this I don't know where else to post this as I'm not sure if it's an OS issue, a PC hardware issue, a network issue, a broadband issue, etc.

I have a 20Mb NTL cable connection which works well.

When not running any internet-intensive applications, my web browsing is super speedy.

But, as soon as I launch a torrent client, my web browsing grinds to a halt.

"OK", I hear you say, "it's another of those bandwidth throttling problems". Well, yes and no

I have my NTL CM which goes to a Linksys WRT54G wireless router. From there, a single cable goes to an 8-port gigabit switch, which then serves the various PCs at home, including my desktop PC and my server in the attic.

If I launch the torrent client on my server up in the attic, my desktop PC carries on browsing the net at normal speeds - I have no slow down.

So, I doubt it's an NTL throttling, nor is it my modem's inability to manage the traffic efficiently - I can only put it down to my local NIC in my desktop PC which has troubles. But there's nothing strange about it Standard MSI P35 platinum running at stock speeds, and using a built-in Realtek 8168B gigabit ethernet NIC.

Interestingly, if I have the torrent client running on my desktop PC which then grinds to a halt, if I then close it, it still takes a good few minutes before normal network activity is resumed. During the slow down, I can't even access my router's configuration page.

Any ideas?

It's to do with the half open TCP connections (I think it's called) as Lourdes pointed out earlier.
Just use another PC or laptop for web browsing if you don't want to "patch" tcpip.sys (I assume you are on XP)
It's not you maxing out your upload as you can browse on other PCs.

[tfboy]

Using 64-bit vista. Will look at the half-open TCP connections.

Not an issue now as my server is back up, but good to know for the future