On Saturday afternoon, my line #3 was unusable for three hours, constantly resynching with crazy rate changes and catastrophic packet loss. The modem is a ZyXEL VMG1312-B10A with the latest our kitizen Johnson firmware in it, the version that contains a continuous SNRM recording and graphical display via http feature. See enclosed a
24-hour picture of SNRM vs time. In a sense, the graph is upside-down, lower values mean higher noise. A forest of downward-going, so high, noise spikes can be seen, and these are overwhelming the modem.
Questions: Do you think this is the correct interpretation? Are these spikes real?
AA recommended that we try banding the downstream to 1-3Mbps sync rate. Recently it has been running at ~3.15Mbps downstream. But I’m not sure that that is enough. Engaging this banding mechanism dropped the sync rate too much, to ~2.858Mbps downstream and also not enough because the downstream SNRM after applying this feature was only 6.1dB and three of those spikes look taller than 7dB high to me. So that would require 9dB target SNRM but that would require sacrificing a vast amount of speed, maybe nearly a whole Mbps, I don’t know, for some very rare event which might only happen once a week or once a month.
Am I missing the point about banding?
When the graph was taken, the target SNRM downstream was actually set to 6dB even though it looks like 3dB. I am aware that I cannot necessarily expect any of the lines to run reliably at 3dB downstream, so 3dB has just been an experiment, but a very successful one, with all lines running very well for two years at 3dB downstream unless there has been a copper line fault.
Today 20:28:28 Today 20:28:36 BT Test xDSL Status Check:Pass Standalone sub test passed successfully. Pass OK.
Circuit In Sync BRAS=2802kb/s FTR=2278kb/s MSR=2848kb/s ServOpt=1 I/L=I
Up Sync=406kb/s LoopLoss=39.9dB SNR=6.1dB ErrSec=0 HECErr=0 Cells=0
Down Sync=2858kb/s LoopLoss=64dB SNR=5.6dB ErrSec=0 HECErr=N/A Cells=0 weaver@a
Today 14:34:32 Update Update AutoTestUntil=0000-00-00 00:00:00-> weaver@a
Today 14:28:34 Today 14:28:57 Test SNR reset: RateBandDS=1472-3072 InterleaveLevelDS=On TargetMarginDS=6dB RateBandUS=32-Uncapped InterleaveLevelUS=On TargetMarginUS=6dB:SNR Recalculation initiated which will enable the line to reach optimum speed, stabilization retrains can be expected over the next couple of days. weaver@a
Today 14:15:58 Tx rate (adjusted) 2737428 to 2462561 (rx 406000) -Auto-
Today 14:14:15 Today 14:14:27 Test SNR reset: RateBandDS=1472-3072 InterleaveLevelDS=On TargetMarginDS=6dB RateBandUS=32-Uncapped InterleaveLevelUS=On TargetMarginUS=6dB:SNR Recalculation initiated which will enable the line to reach optimum speed, stabilization retrains can be expected over the next couple of days. weaver@a
Today 14:12:30 Update Update AutoTestUntil=0000-00-00 00:00:00-> RateBandDS=160-24384.6dB->1472-3072.6dB weaver@a
Yesterday 11:45:57 Yesterday 11:47:01 BT Test xDSL Copper Test:Pass Standalone sub test passed successfully. Pass Copper Line Test Successful DS01:Line Test OK weaver@a
Saturday 17:25:08 Tx rate (adjusted) 2380447 to 2737428 (rx 402000) -Auto-
Saturday 16:29:30 Tx rate (adjusted) 2560234 to 2380447 (rx 355000) -Auto-
Saturday 16:09:04 Tx rate (adjusted) 1624132 to 2560234 (rx 396000) -Auto-
Saturday 15:42:18 Tx rate (adjusted) 2453053 to 1624132 (rx 190000) -Auto-
Saturday 15:28:30 Tx rate (adjusted) 2418479 to 2453053 (rx 376000) -Auto-
Saturday 15:24:53 Tx rate (adjusted) 2503186 to 2418479 (rx 358000) -Auto-
Saturday 15:21:04 Tx rate (adjusted) 2209304 to 2503186 (rx 379000) -Auto-
Saturday 15:19:05 Tx rate (adjusted) 2585300 to 2209304 (rx 358000) -Auto-
Saturday 15:01:45 Tx rate (adjusted) 2364024 to 2585300 (rx 379000) -Auto-
Saturday 14:57:22 Tx rate (adjusted) 2297468 to 2364024 (rx 355000) -Auto-
Saturday 14:49:50 Tx rate (adjusted) 2487628 to 2297468 (rx 355000) -Auto-
Saturday 14:46:35 Tx rate (adjusted) 2510101 to 2487628 (rx 358000) -Auto-
Saturday 14:43:57 Tx rate (adjusted) 2097801 to 2510101 (rx 382000) -Auto-
Saturday 14:40:53 Tx rate (adjusted) 2475527 to 2097801 (rx 341000) -Auto-
Saturday 14:36:14 Tx rate (adjusted) 2239556 to 2475527 (rx 379000) -Auto-
Saturday 14:29:25 Tx rate (adjusted) 2373532 to 2239556 (rx 358000) -Auto-
Saturday 14:25:32 Tx rate (adjusted) 2424529 to 2373532 (rx 358000) -Auto-
Saturday 14:23:53 Tx rate (adjusted) 2500593 to 2424529 (rx 355000) -Auto-
Saturday 14:07:06 Tx rate (adjusted) 2367482 to 2500593 (rx 379000) -Auto-
Saturday 14:04:58 Tx rate (adjusted) 2399463 to 2367482 (rx 379000) -Auto-
Saturday 14:03:13 Tx rate (adjusted) 2421072 to 2399463 (rx 355000) -Auto-
Saturday 14:01:30 Tx rate (adjusted) 2380447 to 2421072 (rx 352000) -Auto-
Saturday 13:59:00 Tx rate (adjusted) 2560234 to 2380447 (rx 358000) -Auto-
Saturday 13:50:32 Tx rate (adjusted) 2341551 to 2560234 (rx 382000) -Auto-
Saturday 13:48:34 Tx rate (adjusted) 1810834 to 2341551 (rx 358000) -Auto-
Saturday 13:46:31 Tx rate (adjusted) 2164357 to 1810834 (rx 376000) -Auto-
Saturday 13:45:03 Tx rate (adjusted) 2385633 to 2164357 (rx 331000) -Auto-
Saturday 13:42:11 Tx rate (adjusted) 1878254 to 2385633 (rx 352000) -Auto-
Saturday 13:35:23 Tx rate (adjusted) 2449596 to 1878254 (rx 289000) -Auto-
Saturday 13:31:13 Tx rate (adjusted) 2260301 to 2449596 (rx 376000) -Auto-
Saturday 13:26:53 Tx rate (adjusted) 2279317 to 2260301 (rx 352000) -Auto-
Saturday 13:22:26 Tx rate (adjusted) 2430580 to 2279317 (rx 358000) -Auto-
Saturday 13:19:14 Tx rate (adjusted) 1637097 to 2430580 (rx 382000) -Auto-
Saturday 11:38:30 Tx rate (adjusted) 2689888 to 1637097 (rx 184000)