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Contention ratio : Where can I find out the answer ?




Is there anyone who can tell me EXACTLY how the contention ratios actually work now and ongoing ? I cannot get anyone from the business support to tell me.  Recently I have had <1MB at some times of the day. With the increase in the use of internet tv, am I to expect the service to get worst and worst. There is no minimum in the contract.


1) What are the current ratios for business accounts ?

2) Do business and home users have separate contention sharing groups and thus infrastructure ?

3) Why cant we have guaranteed minimum to give BTs capacity management teams some hard direction ?

4) Are BT investing in their (non-infinity) infrastructure as internet tv comes of age ?


Personally, being told to use a paying support line to attempt to get this type of information is a bit irritating.

Is there a BT person on this forum who is willing to point me to someone who can answer No 2 ?




BT Partner
BT Partner



1) Contention ratio disappeared when fixed rate broadband was taken away.  Now the network uses management to alter connections based on congestion patterns.  Congestion isn't nearly as much of an issue on ADSL2+, as that uses 21st Century Network.


2) As far as I'm aware no.


3) Because all that would do is further restrict non-fibre broadband.  At present anyone within about 9km of an exchange can, in theory, receive a broadband signal.  The only way to retain that is to make the minimum for broadband so low that it would be irrelevant.


Also there's no way to determine what the minimum on any given line should be.  Every line is different, and so any set figure would again be irrelevant.


Finally on this point there are many factors that could reduce a connection below any minimum figure.  That then becomes a complete nightmare to maintain or regulate.


4) Many exchanges are being moved to 21st Century Network, and so should have access to ADSL2+.  That, however, doesn't help for those at long distance from the exchange, as you'll still get about a meg or less when you get out to the maximum.


Eventually I believe that all exchanges would end up on 21CN, mainly bexcause the new network relies on it to function to its full potential.  Unfortunately any upgrade costs money, in the same way as it does with fibre.


If you want to put in a significant sum of money to aid the infrastructure then I'm sure BT Openreach would love to hear from you.




hi,   thanks for replying.


1+2) I thought as much. I was upgraded to ADSL2+, so I guess I must be on 21CN, right ?

Does your network management dynamically move connections around all your access points in my local exchange then ? Are you in theory effectively just sharing out all the usage evenly within an exchange or is it at a finer resolution ? Just curious 🙂

Does BTs own video on demand service share the same access point infrastructure as me in my exchange or am I insolated from that ?


3) I can see how it would be a nightmare. I already have about max 10MB on my last mile, what I was asking was more about the pinch points further up the chain in the exchange. My last mile is irrelavant if my business line is being congestion controlled in the access points against the other 1000 home users watching Eastenders on iPlayer :-).

I was really curious about what is in store for me as internet tv increases.


Do you not have a concept of different tiers of service that applies to the exchange infrastructure so people who buy more expensive packages will have a chance of downloading stuff in non working hours in the future 🙂


4) :-)).  Sorry, I'm a bit short this month 🙂


Thanks for your time. Sorry about questions, I am just a curious sole.


Also Dave.

BT Partner
BT Partner

Hi Dave (we are legion),


No problem.  Questions are always good.


To be honest I don't know the ins and outs of how the traffic is managed, but I do know that areas shouldn't suffer from a small number of big bandwidth hogs in the same way that they did on the old network.


I suspect that the use of internet TV will have an effect, especially if it's HD, although it would need a fair number of people all using it to have a significant impact.  Obviously that will change in future, but by then hopefully fibre will be much more widespread.


I realise that there is talk of a two tier internet, but right now everyone pretty much shares the same network.  Bear in mind that part of the reason BT still costs more than most is because of price regulation, not just because they want more money.  Blame Ofcom for that one. 🙂