2004-2006 (pre maxdsl) were the worst days for bandwidth.
The demise of 20:1/50:1 contention ratio's started in 2004 when BTw introduced two new forms of charging ISPs, meaning there were 3 ways of paying for bandwidth on the Centrals.
1) Standard based charging - ie with BTw controlling contention 20:1 and 50:1 at the exchange VPs. This was what was advertised as 50:1 etc.
2) CBC - Capacity based charging - contention occurring on the ISP centrals
3) UBC - Usage based charging - ISPs charged for exactly how much bandwidth their customers used.
Plusnet was the first ISP to move over to
CBC which co-coincided with the time they were the only ISP to offer 2Mbps to residential users. They got swamped with 2Mbps accounts, some of them at the time classed as heavy users. Cost of the centrals spiralled and at one point they were having to light new centrals every few weeks, hence why they introduced what became known as the 'Bad Boy Pipes'. Capacity on the centrals was at that time a big issue and in an attempt to keep things under control they were the first ISP to bring in Ellacoya's to help manage bandwidth by using traffic shaping.
Prior to CBC there were some horrendous issues of exchange contention. CBC just shifted the onus on the ISP to control bandwidth at the centrals.
By 2006 all ISPs were using
CBC. 20:1 & 50:1 was dropped because by this point none of the SPs were using the old Standard Based charging. No ISP that Im aware of ever used UBC.
ADSL was now available at most exchanges. CBC lowered the cost of more affordable to the masses and prices dropped quite a lot as the newer lighter users helped balance out costs in some respects, but adsl max meant higher speeds and peak time congestion for many ISPs.
Things started to get better after the roll out of 21CN and
Market Based charging.
- 21CN backhaul is more efficient with much larger pipes (20CN MiSP originally used 155Mb pipes, but most exchanges were upgraded to 622's for dslmax )
- OFCOM allowed BTw to reduce pricing on the Market 3 exchanges which helped reduced ISP costs on certain exchanges.