I'll just alter that slightly...
OHF Errors are CRC errors (there is a 1:1 relationship).
RS Uncorrectable errors inevitably lead to CRC errors, but there can be (and usually is) a 1:many relationship. Any one of those "RS Uncorrectable errors" *will* cause the (bigger) CRC block check to fail. However, due to the nature of noise, where one RS Uncorrectable error occurs, there are often more. And many "RS Uncorrectable errors" can all happen within one CRC block. Once one error has broken the block, it doesn't matter if another 20 break it too...
LOS = Loss of Signal
LOF = Loss of framing
LOM = loss of margin
When modems are sending data back and forth, they need to keep control of it, and be able to exchange control data with the modem at the far end.
For this purpose, they surround your "user data" in frames, and protect that user data with CRCs and (optionally) with the FEC and RS mechanism. The frames provide a way for the modems to identify just where the user data is, and to exchange a few bits of data (so, for example, you can find out the stats from the other end).
If noise interferes with the user data, it gets detected as a CRC error, and reported by the modem that way. If noise interferes with the surrounding framing data, the modem will tend to report LOS or LOF errors. Too many LOS or LOF errors, and the modem decides a resync is needed.
When you have powered off your modem, the first thing the remote DSLAM probably discovers is LOS or LOF. If the modem supports the concept of "dying gasp", then the removal of power gives the modem a few last frames (powered by capacitor) to report a loss of power instead..
Ok, thanks for the detailed explanation, Kitz. It's greatly appreciated. Do you know why the Billion 8800NL doesn't report those LOS, LOF and LOM errors?
Here are my current line stats:
xDSL
Mode VDSL2
Traffic Type PTM
Status Up
Link Power State L0
Downstream Upstream
Line Coding (Trellis) On On
SNR Margin (dB) 9.6 6.3
Attenuation (dB) 25.8 0.0
Output Power (dBm) 12.0 5.8
Attainable Rate (Kbps) 44479 8897
Rate (Kbps) 35000 8447
B (# of bytes in Mux Data Frame) 73 196
M (# of Mux Data Frames in an RS codeword) 1 1
T (# of Mux Data Frames in an OH sub-frame) 0 0
R (# of redundancy bytes in the RS codeword) 6 6
S (# of data symbols over which the RS code word spans) 0.0666 0.7358
L (# of bits transmitted in each data symbol) 9610 2207
D (interleaver depth) 8 1
I (interleaver block size in bytes) 80 203
N (RS codeword size) 80 203
Delay (msec) 0 0
INP (DMT symbol) 54.00 55.00
OH Frames 0 0
OH Frame Errors 0 0
RS Words 4210451360 302016
RS Correctable Errors 857190 51
RS Uncorrectable Errors 0 0
HEC Errors 0 0
OCD Errors 0 0
LCD Errors 0 0
Total Cells 441853571 0
Data Cells 46830735 0
Bit Errors 0 0
Total ES 0 0
Total SES 0 0
Total UAS 30 30
I only powered the Billion BiPAC 8800NL off and on twice yesterday which would mean that the line was still in the green MTBR bracket. So, surely DLM should of taken action, decreased INP and increased the Downstream Rate to 40000 Kbps?
