I run a webmail server (openwebmail with apache under RH8). Openwebmail has a feature called "webdisk" -- it's simply allows you to upload or download files to a folder on the server for storage or whatever. From 3 different client sites (3 different ISPs) I have no difficulty with this. I can upload or download files to/from the webdisk with no problem. However, at a 4th location (a residential Shaw Cable connection in Vancouver) uploads larger than about 50kb stall and eventually time out. Downloads work fine. At first I thought maybe Shaw is throttling upload traffic, but I am able to upload large files to a .mac account from this Shaw connection without any stalling.

It seems the server is ok since I can upload/download from the first 3 locations. Why can't I upload to openwebmail webdisk from the Shaw connection? I've tried various ports (standard and obscure) -- no difference. I've tried uploading from OS X, windoze, and linux boxes -- no difference. I've also tried setting up a Samba share through an SSH tunnel. Works from first 3 sites, but not from the Shaw site.

Can anyone suggest what might be going on here?

For what it's worth, I regularly use scp from my Shaw connected ssh server with no problem. My uploads/downloads are usually 1-5 MB. Also, I've had no problem with occasional bittorrent uploads (several hundred MB at a time).

That's good to know. I am now starting to wonder if there is some quirk with the Linksys router that exists at the Shaw location. It's puzzling.