Entanet (www.enta.net) has been trialling a solution to an ever increasing bandwidth utilisation problem to buy time until additional central capacity is available. The system is explained in a post by Entanet on our forums:
"After noticing severe packet loss on Friday night we have introduced an anti-loss tool. The tool works by reducing the maximum rate limit when capacity hits a certain point and then allows it back up slowly if the capacity returns. [ .. ] The variation in limits are applied on a per central basis so that if only one has a problem then only it has its limits adjusted. Users will be able to switch centrals and the limit will be reset to that of the central they reconnect to.
The rate limit changes only happen once the 5 minute average usage for that central hits 96%, once this occurs then the maximum rate limit is reduced by 500kbps. [.. ] One minute later the next 5 minute average is calculated, if usage remains above 96% then a further 500kbps will taken from the maximum limit and this will continue to a minimum of 2Mbps. [..] Once usage fall below 91% then the rate limit is raised by 200kbps. If the capacity hovers between 91% and 96% then the limit will continue at its current setting."Carol Davies, Entanet
This is rather different from the approach taken by most service providers in introducing limits on usage as the restrictions apply to the whole Central Pipe affecting larger groups of users rather than specifically those downloading a lot or using particular protocols. This rather coarse move is clearly an attempt to ensure that the network performance does not degrade to the point of becoming unusable for most users, although inevitably some will be annoyed by the throttling. It is worth remembering that if it wasn't throttled, the pipe would saturate and reduced speeds and packet loss would still result.
The minimum rate of 2 Mbps below which it will not throttle for an 8 Mbps connection is a generous 4:1 contention ratio. The systems implemented by other providers slow downloads down far more, although they can be more specific on examining the type of traffic and giving priority to particular applications. The success of the system will obviously be judged on how it performs but it is an interesting solution to a problem that affects every ISP at one point or another. If it does provide a practical long term solution, Entanet's implementation may well come at a fraction of the cost of systems users by other providers.
Entanet has faced some criticism from its resellers on the forums for its lack of communication about the testing of this system but the company points out that it needed the testing to be carried out under 'real world' conditions. Several resellers have since expressed support for the introduction of the system as an alternative to the problems caused by congestion or alternative systems.
Entanet have a fourth BT Central Pipe on order which is due to come into service in 3-4 months with the next segment of an existing 622 Mbps pipe scheduled to go live in two weeks' time.