What is wrong with my cable connection

February 1, 2006 11:51 AM

For the past few days, my connection (Comcast) has been driving me utterly insane. I notice that if I am uploading something via FTP, the transfer rate will simply drop to 0.00kb/s and sit frozen until I reboot my computer. Aside of this, I am unable to download torrents, none of them even more, they stay at 0.00kb/s even though I have my client set to use a random port on each use. P.S. I am not using a firewall. What could it be? Thanks in advance.
posted by cheero to computers & internet (12 comments total)

oops. meant to say *none of them even more.
posted by cheero at 11:52 AM on February 1, 2006

Do you have a router and/or modem? Does it start working if you power cycle either of those?
posted by smackfu at 11:59 AM on February 1, 2006

you didn't say what OS you're using or any other details, but two things that come to mind are 1) comcast's utterly shite handling of oversubscribed neighborhoods, which could be exacerbated here, 2) killing your connection with too many flows. more information here, although it's not the only possible culprit.
posted by kcm at 12:11 PM on February 1, 2006

I have been having similar problems. I absolutely could not send files with gmail, and even with with comcast mail it was painful. Everything has been a bit slow, and the whole connection crashed for awhile last night, but uploading has been a nightmare. What is your location cheero? Your profile doesn't say.
posted by caddis at 12:57 PM on February 1, 2006

Right, operating system would be useful to know.

Does your cable modem have a firewall? Are you sure?
posted by unixrat at 1:29 PM on February 1, 2006

If you've been doing a lot of P2P, it's entirely possible (but I don't know how likely) that the cable company is throttling your connections.
posted by Ethereal Bligh at 1:59 PM on February 1, 2006

If you are using Windows XP, two interesting things you can look at when you hit this state:

Open a command window (Start->Run->cmd) and type "netstat -b". This will give you a list of open TCP connections on your machine. On the right is the "state" of the connection. Are a bunch of them "TIME_WAIT"? If so, look to the left and see what exe/process is responsible for these.

These are unconnected TCP connections. A client (or even virus/malware/shitty app) can be holding too many connections open, waiting for response, and Windows won't let you open any more connections.

Another thing to look at: open the Event Viewer (Right Click on "my computer", choose "manage". On the left, find "event viewer" in the tree, expand it. In either "System" or "Applications" (I forget) look for warnings or errors that include "TCP". Open that error, and look for text that says "Reached limit of open TCP connections", or something akin to this.

If you are seeing those errors, that means something poorly behave/malicious is spamming the world, trying to make TCP connections. To limit this, Windows only allows 15 connections to be opened a second.

If these are your problems, now you know what to pursue. Something on your computer needs to be throttled or killed. Sorry I can't be more helpful than that, though...
posted by Dunwitty at 3:18 PM on February 1, 2006

I had the same problem when I had Comcast's (shitty!) cable-internet service. They drop your upstream bandwidth to zero (or close enough) if you upload at full capacity for too long. (I don't think a reboot is necessary -- just stop trying to upload for awhile.)

The "solution" is to throttle your upstream b/w using software (Azureus can do this for Bittorrent, for instance) below whatever your "cap" is. Finding your "cap" might require some experimentation. You might be able to do the throttling with your router instead; I don't know too much about that.

Long-term solution: Find a provider that doesn't suck like Comcast does. I've personally had zero problems with Time-Warner (they don't seem to care how much you saturate your bandwidth). Since T-W and Comcast are likely to overlap service areas, you might have to look into getting DSL or something similar.
posted by neckro23 at 5:43 PM on February 1, 2006

("since T-W and Comcast are unlikely to overlap service areas...")
posted by neckro23 at 5:44 PM on February 1, 2006

the first thing to do is call technical support and ask if you've been capped/throttled, you might get a lecture about "abusing" your internet connection, but at least you'll know that they're doing intentionally

if they're not throttling you, they can run a remote test and see if the problem is with the modem or line

if it's not, THEN try to find the problem on your end
posted by exhilaration at 8:03 PM on February 1, 2006

If they lecture you about throttling, tell them you run a Tor server for Chinese dissidents.
posted by adzm at 9:02 PM on February 1, 2006

Dunwitty's information is incomplete and misleading. The TCP connection limit, which was implemented in XP's service pack 2, is not a global connection limit, but rather is a limit on new connection within a small amount of time that works like a queue, so all of those connections will be iniated. There's only a few types of apps that will try to open a bunch of connections at the same time—some P2P apps are among them. Just web browsing should not cause this problem. There is a hexedit (not merely a registry!) hack if you need to remove this cap. All in all, the behavior you're seeing cannot be what dunwitty diagnoses it as.

I think it's very unlikely that it's your TCP/IP stack that is causing this problem. It's happening elsewhere.
posted by Ethereal Bligh at 10:41 AM on February 3, 2006