ADSL Problems

There are many different reasons why an ADSL connection is misbehaving. Most of the time they can be narrowed down to a very small number of problems. This guide will help you determine where the problem might be.

Slow Connection

By this we mean a you are not getting even close to your expected download or upload speed. There are three main areas that could be causing the problem. Start faultfinding by getting baseline result from a speed test site. Try WWW.SPEEDTEST.NET or WWW.THINKBROADBAND.COM.

Now, the first place to look is in the connection status page of the web interface of the router. When the router negotiates with your local telephone exchange, it will agree a best speed. This is the fastest error free speed that the line between the router and the exchange will support. This is usually determined during the first couple of weeks of a new connection, but can be renegotiated at any time by the exchange. This is what is called rate adaptive, and is why many ADSL connections have speed ratings as up to.., because if are were next door to the exchange that is what you would get. This information will say something like 448 Kbps Upstream, 6112 Kbps Downstream. Compare these numbers to your speed test. If they are very similar then that is the fastest speed your current connection can sustain. That is not to say that it cannot be improved, but that will depend on a number of factors. If you know that your line has been considerably faster in the past, then there may be a problem with the wiring somewhere. See Wiring Problems. However, if you are 5km from the local exchange, then that is probably the best you can get, and you may have to consider alternative technology to get a faster connection.

If the ADSL router says its connection to the exchange is much faster than the speed test result, the next place to look is if anything else on the local network is hogging the connection. Many routers have an ADSL activity light. If you shut down all of the computers on the local network and you still see a considerable amount of activity on the line, then maybe someone has piggybacked on your network. Consider disabling any wireless access points and trying the test again. Remember that there are people who would rather not have their on-line activities traced back to them, and an unsecured network is a real treat, as it will be your door the Police come knocking on. If the ADSL activity light stops flashing when all the computers are turned off, try turning them on one at a time, and allowing them enough time to fully start before moving on the the next. There are many file sharing programs that will use an idle computer to download or upload files. Older versions of BBC iPlayer used a distributed network of everybody's PCs to ease the load on their own servers, until people enough complained about it. You may also have a computer infected with malware sending out spam to lots of people. All of this could be taking up bandwidth.

If during all of the above tests the speed test results remain reasonably consistent, then your connection speed may be limited by the ISP. All broadband connections have a contention ratio. This is the percentage of the bandwidth you are entitled. Some ISP's average it out, some rate limit. In other words, if you have a 2mb ADSL line, with a 50:1 contention ratio, you are only guaranteed a speed or 2mb divided by 50, or about 40kb/s, which is slower than a modem. The original idea was that the likelihood of 50 people all downloading a web page at exactly the same time meant that you would get your 2mb/s for a short burst, and then someone else would use it while you were reading the page. These days, more and more people are streaming Internet Radio and TV, and so the average usage is creeping up, placing presure on the ISP who is buying the bandwidth in bulk. The more bandwidth you use, the more they have to charge you. If you are on a low tariff, they may well slow you down by rate limiting your connection. They will also claim that your speed test is not admissible as evidence as they cannot control the speed outside their network. This is true, so ask them for the location of an internal speed test web page (or ask them to carry out one on your behalf).

Wiring Problems

If your broadband speed has recently dropped, it may be because of a wiring problem. This problem can be within your own premises, or outside, and this makes it tricky to resolve.

The first thing to do is to check the audible quality of the line. You must never forget that fundamentally the line is an analogue telephone line. That is what is was designed to do, and that is why you are paying a monthly line rental. All ADSL does is piggyback on the voice line. It uses audio frequencies that are too high for us to hear, but any noise on the line that you can hear (crackles, pops, or pigeons (a strange sort of cooing sound...)) will also interfere with the ADSL signal. If there is any sort of noise, you must report it to the telephone line provider. The line (and it's quality) is their responsibility (a least until it gets to the master socket). Once the line noise problem is resolved, reboot the router and test again. Remember that the local exchange may need to optimise the line speed again, so even if you get the speed back, the line may reset itself a number of times over the following couple of weeks, and you will notice that the router status page will report different speeds as it hunts for the best.

If the line sounds okay, try disconnecting every telephone device on the line, and plug the router into the master socket. Once the router has booted up and connected, check the line speed on the status page. If it is better, the fault lies with one on the devices you unplugged. If it hasn't, try removing the front panel of the master socket (if it is a proper master socket it will have a front panel with a BT plug that when unplugged will disconnect the rest of the house wiring). Plug the router into the back of the master socket and try again. If the problem has disappeared then there is something hard wired, such as an alarm, that does not have a filter, or a wiring fault.

If the problem has not disappeared, then the next thing to to it to get the ISP to conduct some line tests, as there is a chance the line problem is outside your premises. It may well be a bad joint in a street junction box, or damage during some street works. Just because nothing has changed within your office or house does not mean that nothing has happened in the handful of miles to your local exchange.