BT's performance tester can be found here http://speedtester.bt.com/ . Note that it will only work on BT IPstream based connections.
If your throughput is below 400 kbps, you will be directed to perform a second test, which requires temorarily changing the ADSL username in your modem/router to bt_test_user@yourISP. Where "yourISP" is the normal bit after the '@' in your normal adsl login.
If this test also produces a very poor result you will be asked to reconnect after changing you username on the modem/router to speedtest@speedtest_domain and run test 3.
Test 3 connects you to BT's network bypassing your ISP, so a poor result here indicates that the problem is not caused by the ISP. It may be a line fault, your own equipment or household telephone wiring or a BT issue such as exchange congestion.
A guide to using the BT performance tester is available from here:- BT Performance tester End User Handbook.
If your speeds are poor, but not bad enough to reach test 3 in the normal BT performance tester, it is possible to run the old BT speedtester while connected using the BT login.
The following trick stopped working when BT discontinued the old fixed rate products, replacing them with capped rate adaptive ones.
This test is only intended for fixed rate connections up to 2mbps, so the results are not as accurate as the proper BT performance test 3.
However it can be a useful test if your ISP blames your equipment or BT for your speed issues and you suspect this is not the case, but can't get as far as test 3 in the performance tester.
And open the following link in your browser
If you also have poor ping times on your normal connection and want a rough idea of latency to the BT RAS you connect through run a tracert as below.
tracert -h 3 126.96.36.199
and you'll see something like
1 <10 ms <10 ms 1 ms www.routerlogin.com [192.168.0.1]
2 11 ms 11 ms 12 ms esr4.ilford5.broadband.bt.net [188.8.131.52]
3 * * * Request timed out.
Note only the RAS also known as ESR (Edge Service router) will respond.