Tchibo/O2 selectively throttling download speeds?

[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.

[dg7feq]

The only thing to make sure is to use a) a differnet hardware and b) a different SIM from the same network to see if only you have such slow download speeds or if the BTS has a technical problem (or if you got throtteled by mistake)...

[inquisitor]

I can't explain what exactly happened to you but anything from network congestition to intentional throttling could have happened. Has you signal strength been affected? Then the previously serving cell may face an outage or high load has an impact on link quality (so-called cell-breathing effect). Perhaps some other heavy users "steal" bandwidth from your serving cell or O2 have an issue on their backhaul (especially cells with an microwave uplink may suffer from weather or obstacles). Also plant growth may have an impact on the involved antennas.
Recently I've read an interesting article why network equipment suppliers are offering dynamic throttling solutions, which may be another reason why you've been throttled. I haven't heard about O2 or Tchibo in particular to throttle bandwidth before the monthly allowance has been reached, so I doubt your bandwidth limitation is linked to this.
Btw as you've expressed your interest to use Lidl on another thread please note that Lidl have an additional limitation of 500MB per day on their 5GB plan. So if you ever consume 500MB on a single calendar day you will be throttled until midnight despite you have a monthly allowance of 5GB.

[RobF]

Thanks for your attempts to help me.

@dg7feq

I don't really want to put out the money for a different USB modem and/or a different SIM card just to troubleshoot the present nuisance. Once I know more clearly what's going on I will be bothering Tchibo and/or O2. They are not coming up to their contractual obligations.

@inquisitor

Signal strength hasn't changed; it's been 40-60% for ages (as indicated by Linux NetworkManager, whatever that means).

This poor DL performance started abruptly from one day to the next and has been unremittingly in place for a week, without a break, 24 hrs. a day, even at 4 a.m. It's bizarre that UL speed hasn't been affected and DL speed can at times be tolerable for plain Internet browsing, i.e. webpage loading, but is intolerable for file downloads where it often drops into the ISDN range of 64 kBit/s max., to which DL should be throttled only after the 5 GB allowance for UMTS has been used up.

Re LIDL: I may be interested in using their 5 GB plan for €15/mo in the long term. Thanks for pointing out their 500 MB/day fast access limitation; I probably could live with that. For my present problem with Tchibo/O2, a LIDL SIM is not likely to be a solution, as they use the same network, O2, and the poor DL performance probably originates with the latter.

Or could Tchibo themselves be responsible? Tchibo Mobil completely revamped their customer web interface about 2 weeks ago, and it is still incredibly buggy. Could they also have monkeyed around with broadcasting settings, or told O2 to do so?

Added twist: Tried some file downloads using network protocols other than http. In a file DL via bittorrent got a rate of 2 Mbit/s, in two different ftp DL's got 400 kbit/s (Knoppix distro DL) and 150 kbit/s (Index of /), resp. The very same files DL with two different web browsers (Firefox and Chrome, i.e. using http) were again crawling in at a mere 60 kbit/s. So it looks as though a continuous http DL is affected the most in this performance degradation.

BTW, can I identify the location of the broadcast tower(s) that serve my cell and get their usage statistics?

[dg7feq]

Originally Posted by RobF

Thanks for your attempts to help me.

@dg7feq

I don't really want to put out the money for a different USB modem and/or a different SIM card just to troubleshoot the present nuisance. Once I know more clearly what's going on I will be bothering Tchibo and/or O2. They are not coming up to their contractual obligations.

Of course not, but i guess your friends/collegues etc. have some different hardware.
(sorry i always forget that not everybody has 10+x phones and modems and big packages of SIM cards at home)

[inquisitor]

Originally Posted by RobF

Or could Tchibo themselves be responsible? Tchibo Mobil completely revamped their customer web interface about 2 weeks ago, and it is still incredibly buggy. Could they also have monkeyed around with broadcasting settings, or told O2 to do so?

It's possible that O2 does apply some sort of throttling but I've neither experienced nor heard from such so far.

Added twist: Tried some file downloads using network protocols other than http. In a file DL via bittorrent got a rate of 2 Mbit/s, in two different ftp DL's got 400 kbit/s (Knoppix distro DL) and 150 kbit/s (Index of /), resp. The very same files DL with two different web browsers (Firefox and Chrome, i.e. using http) were again crawling in at a mere 60 kbit/s. So it looks as though a continuous http DL is affected the most in this performance degradation.

These observations rather indicate that there is no intentional throttling since if they throttled protocol-based then bittorent would be the first service to be affected.

BTW, can I identify the location of the broadcast tower(s) that serve my cell and get their usage statistics?

You can locate the basestation (or "nodeB" as it is called for UMTS) by finding out its MCC (Germany: 262), MNC (O2: 07), LAC and CellID and then looking it up it one of the many geolocation databases (see mobile - Public Cell ID databases - Stack Overflow).
A pretty straightforward method is to use Google Maps on your smartphone, on which you would disable WiFi and GPS - then localization is performed only by the cellID, which will result in a rather large blue circle shown on the map, which is the estimated coverage area of your serving cell. The tower itself is usually located somewhere close to the edge of this blue circle as it uses sector antennas covering a 120° angle from its location. Once you get a rough idea of where the tower is situated, check the regulatory authority's map for potential tower locations. If requested the regulatory authority does provide the approval documents ("Standortbescheinigung") for the desired location, which reveals the tower configuration (operator, each single antenna including direction, used radio technology and frequency).
But you won't find any load statistics - that's proabably one of operators' greatest secrets.

[RobF]

Thanks, inquisitor, for the interesting technical details. I'd also found the location of the 3G towers O2 uses in my cell through this link: o2 GIS BTSMap

It turns out I'm located within 1,500 ft. of 4 clusters of antennae on top of an 8-story building. I can see these antennae from my window - there is no newly introduced obstruction.

I'd also posted the present query in the following forum:
Drosselt O2 selektiv die Geschwindigkeit von html downloads?

The two people who replied so far thought that O2 is selectively applying bandwidth prioritization (through selective throttling & traffic shaping?) prior to exhaustion of the 5 GB allotment of fast access, presently perhaps none to their own O2 Netzclub Customers and plenty to Tchibo customers.

If this problem persists, I'm thinking of jumping from my Tchibo XL plan to the equivalent Lidl plan (prepaid 5GB of HSPA/UMTS access for €15/mo). However, Lidl also uses the O2 network. Are there any reports of Lidl/O2 resorting to the same manipulations as Tchibo/O2 appears to?

FWIW, some more details about this problem:

1. The worst aspect of this is the near 100-fold reduction, since late May, of the sustained speed of html DL of files to some 50-60 kbit/s. Interestingly, this throttling is only applied on a per-thread basis. If I download a file with a multi-thread DL-accelerator, such as the Firefox extension DownThemAll!, each thread will be downloaded at 50 kbit/s, so that if I use the max. setting of 10 threads, the file will come down at 500 kbit/s.

2. A name resolution problem at O2's DNS servers does not appear to be responsible for the slow webpage loading. Linux "dig" records quick lookups (100 msec), and when I replace the default O2 DNS nameserver addresses with those of the OpenDNS nameservers, there is no improvement in webpage loading.