[RobF]

I've been happily using the Tchibo/O2 Internet Flatrate XL tarif (5 GB of up to 7.2 Mbits/s speed) with a Tchibo Huawei E173 USB modem for more than half a year, without any major problems and generally getting DL speeds of 1-5 Mbits/s and UL speeds of 500-1.5 Mbits/s. On May 22, I recharged this prepaid account, continuing to get the customary performance. Then around May 25, when I still had 4 GB of data volume available with fast access, the DL performance dropped drastically and has remained at this unacceptable level ever since.

Web pages will still load, generally somewhat sluggishly, but sometimes it may take many seconds or loading will simply time out. When webpages load, at best I may still get a transient peak DL speed of a few hundred kbit/s, and Internet browing is still possible. However, the speed of file downloads is abominable: it generally remains steady at 50-70 kbit/s, so that it may take up to 10 min to DL a 2 MB file. Under these circumstances, it is impossible to DL larger doc files or videos, and Skype constantly terminates VoIP calls (audio only).

Curiously, the UL speed doesn't appear to have changed greatly; I still get 0.5-1 Mbit/s.

This lousy DL performance holds regardless of whether I use Windows or Linux with this modem on the Tchibo/O2 network and whether I use my laptop or my netbook, the same ones with which I used to get good peformance. Moreover, nothing was changed in the network config settings of the various network managers I'm using (NetworkManager in Linux, Mobile Partner or MWconn in Windows XP). Also the location of the modem remains the same as before, and there is no change if I move it by a few meters.

The LED on the modem and the network icon in the system tray consistently indicate that I'm connected via HSPA or UMTS; the connection alternates between these two.

Files from the same sites (e.g. Scribd, mediafire, youtube) that are DL at a snail's pace via GMS/O2, when DL on the same computers at the same time via a WLAN/DSL connection come in at a good clip, e.g. at several Mbit/s. So it's not the websites that throttle file DL speed.

I'm forced to conclude that Tchibo/O2, as of almost a week ago, has selectively throttled the DL of files to unacceptable levels. Is that conclusion waranted, or is there another explanation? Why would they do this? Is there a precedent? Is this likely to be a technical problem or an accidental misconfiguration that would be cleared expediently? Where could I find out what happened or what O2 might have done? Is there a website at which users would post their complaints about such a problem?

Tchibo CS seems to be of no use; they haven't responded to my complaint filed 5 days ago.

Thanks for your help.