dynamo52 writes "I am a freelance network admin who mainly services small business clients. Over the last few months, I have been noticing that anytime I have run any type of bandwidth testing for clients with Comcast accounts, the results have been amazingly fast; with some connections, Speakeasy will report up to 15Mbps down and 4Mbps up. Of course, clients get nowhere near this performance in everyday usage.
Upon further investigation, it appears that Comcast delivers this bandwidth only for a few seconds after any new request and it is immediately throttled down. The only way to get any type of accurate estimates are to actually download and upload a significantly large file (100MB+). Doing so yields results more in line with expectations (usually about 1.2Mbps down and about 250Kbps up but it varies).
My main question is this: Is there any valid reason Comcast would front load transfers in this way, or is it merely an effort to prevent end users from being able to accurately assess their bandwidth? Also, does anybody know of other ISPs that use similar practices? This can be quite annoying when trying to determine whether a small client really needs to switch over to a T1 or if their current ISP will suffice."