Background Info:- ISP - Sky 40/10 Unlimited Fibre (FTTC)
Modem/Router - Billion 8800AXL Connected to ECI Cab
Distance to cabinet approx 800m (rounded up to allow for cables up/down poles). According to BT OR man. some of the cable run is Aluminium, although approx 150m of aluminium was swapped for Copper back in the Autumn) with my attenuation figures dropping from around 25.7 to 25.2dB
Have had this service for around 3 years now. Speeds have not been great (varying between 17.5 - 20.0 Mbps throughput DS and 4.5Mbps US), but have been consistent.
Just before Christmas, noticed DLM kicking in and speed gradually dropped to under 10Mbps DS, so logged a call with Sky who blamed my internal wiring. But that's another saga best left for another day.
Upshot - BT Openreach attended (15th Dec) and diagnosed high resistance joint on my line using his TDR, which he located and attended to. He was able to reset the line (to fast path?) and tested for speed and CRC's. He declared it good with a connection speed of just over 21.5Mbps down and very few CRC's (at the time).
I subsequently started monitoring line stats and logging to MDWS (username Scarab). I didn't expect my line to stay on fast path but have been surprised at the very high CRC bursts along with error seconds ES and severe error seconds SES counts following a few line resyncs and various levels of interleaving being applied.
I don't have MDWS stats dating back to when I received a more stable 17.5 to 20Mbps connection BUT I am fairly certain I never saw such huge bursts of ES/SES! I seem to remember the ES counters going into the low 100's (and SES being far less) even when I rarely reset the Billion's counters.
I am wondering if my line is suffering from random noise burst problems (thus the bursts of CRCs followed by stable CRC counts)? I can't think of anything that has changed internal to my house to be causing noise. I guess noise could be injected virtually anywhere along the cable run but I cannot identify anything obvious - ie roadworks, generators running etc
My other theory for the change I have seen is that the aluminium to copper change a couple of months ago saw me connected to a pair that is just suffering from a higher level of crosstalk than previously. If so, I want my old aluminium pair back! Would crosstalk manifest as bursts of high levels of CRCs? Or would the CRC errors tend to occur at a constant rate?
I am guessing that DLM is doing its thing, but I would appreciate it if some of the Kitz 'gurus' could cast an eye over the stats before I refer this back to Sky again.
Thanks.