Broadband Speeds FAQ

Q: What is the speed of the broadband service?

A: The advertised speed of any broadband service usually refers to the copper wires between your premises and your local exchange, which is the only part of the service that is dedicated for your use only. From the local exchange onwards you will always be joining a shared backbone network so the ‘speed’ you actually experience can be heavily influenced by the amount of other users and what they are doing. This is true of all broadband providers no matter what technology they use to deliver the service.

Q: Why is the advertised speed not always what you get?

A: All providers use the same copper exchange lines to deliver service, and all of the technologies used these days tend to be what is known as rate-adaptive: that is, rather than offering a fixed speed, within the first ten days of service they will settle on the highest stable rate your line can support, which could be anything within a certain range. The rate that your line settles on will be affected by factors such as the length of the line itself, the quality of the copper, and the amount of local electromagnetic interference, which usually don't change from one broadband provider to another. This means that the speed of your local line will be very likely to remain the same from one provider to another regardless of the speed advertised.

Only users who live very close to the exchange, with high-quality copper pairs and no local interference will get even close to the maximum speeds advertised. Despite some providers claiming to offer services up to 20Mb/s, the average speed of broadband lines across all users in the UK actually runs around a more modest 4Mb/s level so most users will not actually be able to achieve this speed even if the provider's technology offers it.

It should also be noted that with rate-adaptive broadband this speed can change: for example, an increase in local interference can sometimes mean that a line drops down in speed, although it should also eventually return to the previous speed if the interference returns to previous levels.

The other thing to bear in mind is that there are many different reasons why a service can run slowly. It could be a problem with the website itself. There could be a lot of congestion in your local exchange. Quite often, slow speed of service has nothing to do with the speed of the local exchange line.

Q: So is the advertised speed irrelevant?

A: No. Although it is not as important as some might say, it is still true that the speed of your local exchange line represents a maximum speed of your service, as data can only be transmitted as fast as the slowest part of the connection. The shared backbone network runs much faster than your local line, but is also shared by many thousands of other users simultaneously.

Q: What different speeds are available in the marketplace?

A: When broadband was first launched it only came in three fixed-speed offerings: 512Kb/s, 1Mb/s and 2Mb/s. After a while these came to be replaced by the first rate-adaptive offering known as MAX which offered speeds of up to 8Mb/s, although always variable and alwasy dependent upon factors such as line length etc (see previous question above). Recently, a new rate-adaptive technology called ADSL 2+ has been rolled out by some suppliers in some areas, which offers much higher headline rates (potentially up to 20Mb/s). However, only users who had a high speed before on max (such as 7-8Mb/s) are likely to benefit from this increased capacity. Everyone else will see little or no change in speed when moving from one technology to the other, so for the most part, users should expect to average around 4Mb/s whatever supplier or technology they use.

Claranet has conducted successful trials of ADSL2+ technology and will soon be rolling it out as a standard option. Because there is no guarantee that ADSL 2+ will increase a given customer's speed, we are looking into the possibility of offering this as a free upgrade for the same rental as current services based on MAX. Precise details of the offer will be confirmed shortly before launch.

Q: What is the difference between speed and usage limit?

A: The usage limit of a broadband connection is the amount of data that you can send and receive over that link in a given period (usually a month), irrespective of speed. Everything you do on the internet involves downloading data to your browser, and the volume of this data is counted to ensure that it remains within a specified limit. A faster link does not mean that you automatically use more, although it may be the case that you start to do more on the internet when you find your line is running faster.

Q: What about fibre-optic technology?

A: Fibre-optic technology offers much less signal degradation over distance, as well as being less sensitive to interference, meaning that it offers the prospect of more consistent speeds for users from place to place regardless of their distance from the exchange. However, it still does not change the basics of how broadband works in that you will still use the fibre-optic local tail to access a backbone network shared with thousands of other users. This means that whilst it helps, it does not in and of itself guarantee higher overall speeds or a higher quality of service. Whilst BT has been considering plans to ramp-up fibre optic deployment in the UK for some time, it remains a technology that has only been rolled out to a fairly limited geographical area, so most users remain tied to traditional copper pairs. Claranet Soho will be keeping a close eye on developments in this area, with a view to launching new products as soon as they are available.

Q: What is the difference between bits and bytes?

A: Computers talk natively in binary code – a stream of ones and zeros (eg : 0011100011). A ‘bit’ is a single one or zero, and line speeds tend to be measured in terms of how many of these bits can be transmitted in a second (so 8 megabits is 8 million ones or zeros each second). File sizes and disk capacities however, tend to be measured in ‘bytes’, which are simply blocks of eight (8) bits. So if you want to go from bytes to bits you must multiply by eight, and if you want to go from bits to bytes you must divide by eight. Your line speed is advertised in mega (or millions of) bits per second, but your usage limit is measured in Giga (or billions of) bytes per second. However, this is only approximate, as broadband networks add overhead so only very crude calculations of expected download time can be made using these basic numbers.