Last year we published the distribution of our customers speeds in order to compare what our customers were starting to see on our 21CN network against what they previously had and also to see what speed distributions both 20CN and 21CN were giving. As we have over 800 customers on 21CN now we thought it would be useful to revisit the distribution of speeds as we have a much better sample size now. More…

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Today’s article from the BBC ‘Test your broadband speed’ has been interesting but hasn’t really told us anything we didn’t already know.  Since ‘Broadband Max’ was introduced in 2005 we’ve always known that the broadband speeds you experience can have many determining factors, such as distance from the exchange, line quality, capacity at the exchange and external interference. We’ve talked about many of these things in articles such as our ‘Advanced Guide to Broadband Max’ and ‘Get Ready for High-speed Broadband’. More…

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Ever had a random sync-speed drop that resulted in slow throughput for days?

The necessary evil of MaxDSL (otherwise known as the IP Profile) is the throughput cap that BT assign to customers’ lines. It’s designed to stop packet loss within BT Wholesale’s ADSL network and, working alongside our own Maximum Rate for your connection helps to improve end user performance by ensuring the traffic is intelligently managed from end-to-end.

The IP Profile and bRAS profile for customer lines react to fluctuations in sync-speed (the speed at which you connect with the telephone exchange). That means that if your connection speed drops – then the IP Profile limit swiftly follows suit. In turn, we then receive an update from BT which updates our own limit for customers’ throughput. The net result is a better performing line at lower sync-speeds and therefore better performance in some fault cases.

Fluctuations in sync-speed can be caused by a variety of things. Storms, for example, can result in a reduction in sync-speed and you can also affect it by plugging telephone equipment into the line without a microfilter. A line fault could also result in increased noise on the line and therefore a lower sync-speed.

The inconvenience occurs, however, when everything returns to normal. That is, everything except your IP Profile. As explained above, it doesn’t take much to trigger a decrease of your IP Profile – that all happens smoothly! But currently it can take 3-4 days of a stable sync for it to go back up and that is what BT are now changing the logic of.

From 7th August, BT Wholesale are introducing what they call “Adaptive Rate Logic”. Essentially, this means more granular management of the sync-speed to IP Profile relationship. Under “Adaptive Rate Logic”, raising the IP Profile after a sync blip will be based on the percentage increase monitored. Lines which quickly come back up to normal sync-speed will see the IP Profile lifted within just a few hours in most cases, whilst lines with a sync-speed that increases more slowly will result in a longer wait and thus proven stability of the line before the IP profile follows.

BT’s briefing to ISPs stated :-
“The current Max logic rules mean higher sync rates are required to be sustained for 3 days to invoke an upwards BRAS profile move, irrespective of the degree of line rate change.

This way any lines that have dropped to an artificially low line rate for any reason ( e.g..
thunderstorm) and revert to a higher line rate soon after may only need to wait a short time for the higher BRAS profile to be invoked.”

If you wish to find out what your IP Profile is then try a BT Performance Test at http://www.speedtester.bt.com

If you think you might be suffering a speed fault, have a read of James’s excellent blog post here : http://users.plus.net/QL:8831BC49

Liam Martin
PlusNet Comms Team

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