Wednesday, 12 August 2009

Basic Information on Your Speed and Connection

The same symptoms of broadband problems - slow or falling speeds recur time and time again on the BT Beta Forum and other similar forums. Inevitably, the same problem requires a very similar answer, so here are the basic things you should do.

1. Collect the Basic information - The first thing to do is to collect you basic router stats. If you don't know how to find them, look here on the Kitz page for your particular router. They will look something like these.
Click on the picture to see an enlarged view. For the moment, the four most important sets of values are the System Up Time (Connection Time or similar), Connection Speed (the sync speed), Line Attenuation and Noise Margin (or SNR Margin). If you want to know what these represent, the Kitz website provides a useful guide here.

2. What Speed Could You Be Getting - this is a fairly difficult question, but you can get an idea by taking the Attenuation figure and putting it into the Kitz Maximum Speed Calculator. In my case, the Attenuation is shown 63.5 dB (its actually 68dB), but most routers will not record anything above this, so if your attenuation is 63.5 dB, what follows is very much a best estimate.

Now you can check to see what BT claim you should be getting. Kitz, thoughtfully, has another checker to help. Try this once with your post-code, once with your phone number and finally with both your post code and phone number. You may find a marked difference between them. My results are 1500kbps, 500kbps and 500kbps - a wide range of values. You can also get two measures of distance from the centre of your postcode, to the centre of the postcode where the exchange is situated - the direct 'as-the-crow-flies distance (3.44 km) and a calculated road distance (5.79km). In most cases, your actual line length will lie between the two values and be closer to the road distance. Unfortunately, some lines take circuitous routes and could be longer than those predicted. Thanks to BT, I know the exact line length between the exchange and the PCP (the green cabinet)is 3.361km and adding another 400m for the line length between the PCP and the house, gives me a line length of about 3.8km. Unusually, my line travels in virtually a straight line.

3. Your IP Profile - Now you need to run the BT Speedtester (NB You need Java TM installed on your computer for this to work). The important value here is the IP profile, in this case it's 1250 kbps. This fits with the sync speed of 1472kbps found in the first test and this one. With this IP profile, my throughput speed, the speed I can actually expect for downloading, is 1142 kbps. Compare that result, with this one, taken from the same line a few days earlier. Here, the sync speed is a little higher, but the IP profile is only 500kbps and the throughput is a pitiful 382kbps; a quarter of the throughput in the earlier results.

This last set of results show there is a problem with this connection - in this case it's a type of interference called Repetitive Electrical Impulse Noise (REIN). REIN causes the router to lose sync and the DLM at the exchange forces the IP profile down and the Noise Margin up(see first picture - Noise Margin = 12.9dB).

One last thing to do. If you are confident you have an accurate figure for your line length, you can ask the question - What attenuation and speed should I be getting? To work this out, go back to the Kitz Maximum Speed Calculator and vary the attenuation until the distance figure matches the line length you calculated earlier. For a line 3.8km long, a reasonable attenuation would be 53dB and the IP profile should be 3500kbps. Clearly, there is something badly wrong with this connection and in this case, it is because it links to the exchange with an old aluminium line, which suffers 50% more attenuation than a copper line of the same length. Remember though, these are only guideline figures and only as good as your calculation of the line length!

OK, now you have got all the router information you need to ask for help on the forums! Please take out any personal data, like IP address, home address and postcode before posting your stats on the internet!

No comments:

Having had some major problems with my own broadband service, I understand how others struggle to get help from BT.

There is a lot of good information out there, but it can be hard to find. So this blog is an attempt to pull some of it together, in one place.

It's a blog that really shouldn't be needed - if only BT and possibly other ISP's in the UK, provided useful customer support.