How are line speeds estimated

[tehidyman]

I contacted some ISPs some time ago to see what speeds I could obtain if I changed to an LLU supplier.  My recollection is that they estimated little more than my ADSL2 connection at the time - about 3meg.  My download speed has now fallen to 0.7meg. and asking LLU ISPs the same question I get answers of about 1.5meg.  When I was with an LLU ISP I got 3.5 meg.  So where do they derive the estimates.  The exchange is still the same distance away, my attenuation is still the same and I have a more up to date router. 

[Rik]

I don't know how LLU providers calculate it, but BT start by providing a guesstimate based on distance from the exchange. They then refine that to reflect speeds actually achieved. It may be that LLU operators have access to that data through BT Openreach. Lines are degrading, joints are failing for example, and there is increasing cross-talk as more and more people take to the net. This all produces reduced speeds compared to a few years ago.

[Glenn]

http://www.kitz.co.uk/adsl/max_speed_calc.php has a checker, where you can input you figures, it then gives a guess at the speed.

[tehidyman]

Just ran the calculator that Glenn recommended.  LLU figure is 3904 kbps with a throughput of 3455kbps so now  I puzzle as to why the ISPs give less than half 

[Rik]

BT profiles are part of the story.

[Technical Ben]

Hedging their bets?

[Rik]

Saving their costs.