Steve Powell, Product Manager for Connectivity & Security Services at Viatel, notes that the press coverage of the report so far seems to be concentrating on how these results for average speed reflect poorly on service providers, drawing the inevitable conclusion that end users are not getting the service they paid for. He feels this is too simplistic and runs the risk of confusing the issue further.
“The ‘speed’ of an ADSL based broadband service not only has the issue of contention or congestion within various networks including the public Internet, but ADSL also has to deal with another limitation, this is the line rate or synchronisation speed of the line itself. The speed at which the equipment* at each end of a broadband connection on a phone line can successfully establish communications. This speed depends on the quality and overall length of the end users phone line. Data can only flow over this link once the speed has been negotiated by the equipment at each end.
ADSL1, the technology employed on the majority of ADSL services available within the UK can provide a maximum line rate of 8Mb/sec, ADSL2+ the later version of ADSL being rolled out as part of BT’s 21CN network and by many LLu providers can link up at a maximum of 24Mb/sec. However under both ADSL versions, the maximum line rate will drop with the length of the copper wire on the individual phone line. 10kms away from the serving exchange this will drop to a maximum of less than .5Mb/sec. So line speed is set by the individual user’s telephone line.
The other consideration is the level of contention or congestion that may hamper the flow of data over the established ADSL circuit. This can be within the serving exchange, within the national BT backhaul network, within a service provider’s network or out on the Internet itself. It would be fair to say much congestion is forced onto the service provider’s network at the point of aggregation from BT, by the huge cost of moving data from the end user’s connection to the service provider, which forces providers to squash more users onto the available bandwidth in order to maintain a cost effective service.
I think this is a very important issue for UK broadband users, that people need to be made aware of, but the national press needs to provide more information as to the real issues affecting speed when reporting, to avoid further confusion and explain exactly why service providers can only offer an “UP TO” ADSL service.”