Strange upload slowdown issues - help!

You might want to post this in alt.online-service.comcast . - RM

I agree. Isolate the issue as much as possible by taking out servers you don't have control over, and networks which may have congested peering points. And get rid of any other sources of traffic within your own network.

Keep in mind that if you're trying to download - even just web browsing - at the same time, there will be acknowledgements that need to be uploaded. Those packets will cut deep into your uploading capacity.

Now does this happen at all hours? For example, does it do it at 3am, when your neighbors are all asleep? Or does it just happen when you are really sharing the upstream with everyone else on the block? It wouldn't take too many people attempting to stuff the pipe at the maximum bandwidth before the upstream channel is saturated. And when that happens, the network favors the nodes trying to send less data over those that have an endless stream queued-up.

Also, your PCX1100 is an old DOCSIS 1.0 modem; the first generation from Toshiba. Whatever tech support is left for this modem is going to be fairly limited, so it's possible that whoever wrote the latest version of the config file being downloaded to the modem has run into some quirks that weren't a real issue in the days when the modem was new. So there is an outside chance that it is a modem issue.

Try uploading a 20MB file to your Comcast online web storage as a test since this is completely "in network". [25MB is the current file limit?] I have always seen maximum possible upload speed doing this; i.e., on my 256kbps rated upload, 30KB/s +/-. The problem might reside in your upload destination. When doing this, make sure your other computers are *not* accessing the internet if you are running with one IP address behind a router since their activity is shared with yours.

Excellent - thank you guys for your input. I will try the Comcast server upload. Yes, it happens at all hours - very predictable behavior, too. I am already lined up to snipe a PCX2600 off of ebay...

OK, I FTP'd a large file to my Comcast personal web space. Same behavior!

Think it could be my PCX1100?

Ok, that pretty much puts the problem in your system/equipment. Since the problem persists when directly connected to the modem (you did reboot the modem when directly connected?), then it's either the modem or the line. What are the upstream/downstream parameters reported on the modem's web interface http://192.168.100.1/ ?

What is the file extension for the large file? If it's *.avi, try a comcast test after changing the file extension. There was a problem in XP with *.avi files and slow transfers due to XP reading the file into memory for any Windows Explorer operation. There is a registry fix for this, but I'm unable to find it right now.

OK, here is a link to some "fixes" that might improve file handling, if this is the source of your slow uploads. Note that these are pre-XP SP2. I note that the problem with slow file transfers I had were the original XP without service packs and the suggestions here solved the problem. I have SP2 so these changes were probably restored in my registry with the SP2 update. If you make any of these registry changes, save (export) the key so that you can restore it later if the change doesn't help:

Thank you for the chance to provide feedback. I have used Vonage VoIP for several months. I have the Toshiba PCX1100 which I have used for several years to surf the web with no issues. When I moved to a different area in Dallas, I noticed my VoIP was terribly degraded from me to caller, (choppy audio upstream) to the point of seconds of cutoff audio. Also, my TiVo which had been connecting fine over VoIP had completely stopped working over the last two weeks. Could NOT connect. To make a long story short --- I searched forums and found that the PCX1100 was a prime suspect and advice was to replace with Motorola SB1100. I did this and ALL PROBLEMS RESOLVED IMMEDIATELY. So as a troubleshooter I am trying to get the word out as best i can: If you have any broadband issues, and you own a Toshiba PCX1100, do not waste any time troubleshooting until you replace that cable modem.

Thanks again and good luck to anyone who might benefit from this.

I assume you meant the SB5100?

So your PCX1100 flaked out, or your new cable provider didn't support it properly, or it was coincidence your cable provider provisioned your new modem properly, or etc.

Who cares? I don't think "anyone will benefit from this."

Well, an update to everyone who helped. Somehow the issue resolved itself, and I can't even figure out why. Something tells me it had to do with Comcast, who has been upgrading Dallas access speeds lately. In any case, my PCX1100 was working fine again - of course, after I had already received a new PCX2600. So I went ahead and installed the 2600 just to be on the cutting edge....

Now I get a steady 330Kbps upstream.