- Joined PlusNet around Jan, when you say im sync'ing at 19999 up I shouldn't be getting 39999 down, do you mean it indicates I should be getting more down?
Openreach sell packages (to ISPs) at 40/2, 40/10, 55/10 and 80/20. The speeds are limited by Openreach in such a way that means the modems will not sync any higher than the package speed. So ... the only way to have a 19.999Mbps upstream sync speed is with an 80/20 package at the Openreach wholesale level.
However, the 80/20 is a maximum ... and other limitations can restrict your actual sync speed. The most obvious limit is distance - where a long line simply cannot attain a sync speed of 80 Mbps, so settles for something lower.
The other limit is an artificially-imposed one, where BT's quality-monitoring process "DLM" decides that your line is too unstable (too many bit errors, or too many resyncs), so imposes a lower speed limit in one or both directions. When this happens, it is known as banding, and usually results in a sync speed that is a few kbps below the band. 39.999Mbps is often seen as the sync speed of a 40/2 or 40/10 package, but it can also appear as a "banded" sync speed for a 55/10 or 80/20 package.
When you combine the analysis of both upstream and downstream together, it looks like you have an Openreach wholesale package of 80/20, where the downstream has been banded (by BT's DLM process) to a limit of 40Mbps.
- As above joined fair few months ago, speed has been consistent - at start it was higher as I checked to compare and was around mid 50's but that was before any initial training etc.
The "attainable" speed gives you some idea what you could achieve if the banding weren't in place. Your's reads 52Mbps, and you probably could get that - and probably used to.
You also have to remember that, as takeup has increased, so has the interference from crosstalk. FTTC suffers from this more acutely than ADSL, and as the consequent noise increases on a line, speeds drop somewhat and bit errors increase.
