Today I had a look at a friends Internet connection that was not playing ball. It was a BT Broadband connection, via a Voyager Voice Router. Everything looked good, but the connection was appallingly slow - as in less than 120 *bytes* a second. Yes, bytes. It was quiet a surprise.
Ping tests and traces all came back relatively normal - no latency issues. The router indicated a sync rate of full 8Mbps, with no major problems.
Attenuation, SNR etc were all REALLY good - the exchange is around 200 meters away - literally on the other side of the road.
But still the connection sucked. I suggested that they contacted BT, but knowing what their helpdesk is like, I wish them luck ... would be interesting to see what the problem is...