I've experienced progressive speed reductions on my FTTC connection over the last couple of months. My sync used to be a solid 56Mbps with 6dB SNRM and minimal errors but at the end of February the SNRM dropped to 3dB. The 56Mbps sync wasn't affected until three weeks later when I lost connection and had to reboot at the lower rate of 48Mbps.
The following day throughput had dropped to 9Mbps downstream and 0.12Mbps upstream so an engineer was sent. He reset the connection but the sync was lower still at 38Mbps with 6dB SNRM, sadly above the BT line speed estimate of 35Mbps. Several DLM-sensitive reboots later I was stuck on an exact 40,000Kbps sync despite there being no banding or cap.
A subsequent GEA test found an impaired junction but the engineer sent to fix that made no measurable difference. The next engineer checked the line back to the cabinet and determined that there was an AC imbalance on the dropwire. He changed the last 50m or so of overhead cable and downstream attenuation improved slightly from 26.2dB to 25.9dB but sync was back to 38Mbps again. After a couple of days there was a network initiated resync as G.INP was re-applied and I'm now on 44.7Mbps, so around 11.3Mbps down on what used to be normal.
There's now nothing apparently wrong with the line and I live in a rural area so have my doubts about the possibility of hordes of new users all coming online at the same time and eating up bandwidth. If the slowdown had been more progressive I'd have accepted the contention argument but I feel that there were sudden changes. Having tried three different routers and given DLM ample time to settle I've run out of options.
Maybe DLM isn't working as intended or has gained sentience and taken an arbitrary dislike to me. When I was on ADSL broadband with an LLU supplier it was a great relief to be free of BT profiles and over protective DLM which would limit me to painfully slow speeds for three days if offended. There are two LLU suppliers listed for my exchange but it's not clear whether they just provide a slightly more independent ADSL service or an FTTC connection which might let me have whatever speed the line is capable of without profiles and aggressive DLM. I don't want to switch to Talktalk and find that they are just reselling the BT product.
Edited by spinynorman (Sun 12-Jun-16 19:35:09)