FTP Download Slower Than Upload

I have a client that's asking me a question that I don't know where to start to look or why it would be doing this.

My client is primarily a FTP user (they're a marketing firm and use my server to exchange large files -- 700mb - 1GB -- via FTP). The client says that for downloads, they get an initial speed of about 475k. Then right near the 4MB mark, it slows off. It will slow over the course of a couple minutes down to about 100k and stay that way until the file is finished.

For uploads, they get a pretty solid 500k throughout the entire file.

This client never really gripes about anything, and my contact there is a smart dude, so I wouldn't expect he'd be griping unless something was really wrong

If they're uploading similar-size files to other servers at other datacenters, it works fine, and gives them consistent 500k-ish through the entire download. They have 3 T1 lines at their office provided by a local ISP. They're usually transferring a single large zip file.

I'm running WHM 11.26.18 on my server on CentOS 5.2 running Pure-FTPD. I'm also running configserver.com's firewall software and have whitelisted that office's IP address. I've left the Pure-FTPD config alone in cPanel, other than to increase the maximum connections per IP address slightly. Load is low on the server (always less than 1, usually less than .20).

Any ideas or something else I should ask them that I'm not thinking about?

Thanks!
-Jake

 

Well, this is a small town and there aren't too many cPanel users around here (let alone folks using that ISP), but I'll ask around, and maybe see if he can try it on another ISP locally.

He did however try it via Comcast in Portland (Oregon) and had no problems at all, so <shrug>. I'd say an ISP problem, too, but I just wanted to make sure all my ducks are in a row.

-Jake