Drop of SNR in working hours

[#1]

HI Alastair,
I'm not sure what we can find out from this end but I'll ask.
Jojo

[#2]

Thanks Jojo, you're a star.

[#3]

HI walker23,
I've just been speaking to one of the faults guys and there's not a lot we can test from here. I did see, however that the last agent didn't think it was a REIN issue, but I have just been explaining how we had already checked the contention and they are now getting on to the escalation owner to make sure you get the REIN engineer.
Jojo

[#4]

Thanks again Jojo, anything to try to get it back on track.
I'm at work at present but I can remote access my laptop, it keeps dropping the remote access and will not run the BT speedtester (page part loads then stops), I saw around 800000 CRC errors downstream in about 4 hours earlier today (in between remote access drop-outs).
I remain convinced there is interference on the line.
Thanks again,
Alastair Walker
(walker23).

[#5]

That's what my feeling is too.

[#6]

Hi Walker23,
I've just looked through this thread, and can see you're having horrendous problems. The gut feel here would be bad REIN problems.
The most striking thing I can see is how your downlink CRC graph changes from a straight line of 0 faults, to a straight line of 200,000 faults per hour. I think you are right - it is this rate of faults that means your line is not capable of sustaining *any* level of TCP/IP traffic. Here's why (or at least my understanding of why)... hope your maths is good.
Our downstream data is carried by ADSL from DSLAM to modem in "frames", at 4000 frames per second. 69 of these frames are built up into a superframe (although only 68 carry our data), and each superframe is CRC-checked. That means there are approximately 59 CRC checks going on every second. The frame rate seems to be constant, no matter what sync speed you have.
If I'm right with the theory there, then that makes for 211 thousand CRC checks per hour.
Your 2 graphs (and 1 written figure) seem to show these kind of error rates:
- 13/3: 1.4 million CRC over 7 hours (200,000 per hour)
- 16/3: 560k CRC over 3 hours (185,000 per hour)
- 17/3: 1.6 million CRC over 8 hours (200,000 per hour)
Thats a failure rate of around 95%! That kind of failure rate is going to see the kind of problems you experience, with pages failing to load all the content etc. I suspect that if you didn't have DLM turned off, then you'd have almost no connection whatsoever!
Of course, this depends on my theory being right about how often CRC checks happen, and depends on your router presenting valid data, but the numbers sure look suspicious.

[#7]

Hi WWWombat,
thanks for the very interesting figures, I had wondered why I got a straight line graph regardless of whether the line was actively being used for internet traffic.
Your estimate of around 95% loss certainly matched how the line 'feels' when this occurs as it slows down so dramatically it could easily be 5% or 1/20th of its normal speed.
Thanks again for the info.
-  Alastair (walker23)