Bearer 0 is your sync line. The Max line, (or Attainable in some other presentations) is what the line could achieve if Openreach weren't capping it at 80/20Mbps.

In reply to a post by bsdnazz:

DSL stats says the link has been up for 2 days, 18 hours and 44 mins so clearly there's been a drop and reconnect.

I was just going to point that out to you. It's the last section in the stats you posted .

Well that didn't last. After just under a week I had a resync at 13:31 today at 64536 (Reason: 1 Remote Defect Indicator/DLM) and my attainable is down to 63932 from 82488. I wonder what caused the jump and why has it reverted to where it was?

If anyone is capable of interpreting the great long string from modem_stats.log:

Before:
05/11/2015 13:31 66999 19999 5.3 9.2 14.0 6.9 82488 16368 PTM 1070 4430 1683170 65154 0 0 553562 0 485 7168 0 153.767 290947 27058 7168 0 4205415 0 485 750 485 3490668080 1529473 3171552 0 0 0 16 1 22 2341 20 31 10 10 20245 633305 15085 0 4.3 21.1 32.2 0.0 11.2 26.6 41.3 4.3 21.2 32.1 0.0 13.3 26.2 41.2 10.6 8.0 9.7 0.0 5.6 5.3 5.0 -3.4 -22.4 6.6 0.0 11.5 7.9 7.0 Showtime 1 1 L0 17a ON ON No Showtime 16.4 0.0 158 237 1 1 0 42 8 16 0.0754 0.3781 17724 5374 0 0 0 0 2601818657 0 1414376953 0 0 0 0 63 52 49.00 0.00 0.00 3.98 0.00 0.00 0.01 64.22 418392 964 VDSL2 46 4 49 0 0.00 0.00 0.00 0.00 0 0 1 0 0 0 10 0 0 0 1 0 1 0 G.INP 0 0 16 0 7 0 42 0 14 0 18 0 14 0 0 24 3 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 34462505 0 3735 0 0 0 0 0 344624436 0 2596 0 2593 0 0 0 0 0 70090 0 46 0 28512 0 26 0 69244 0 27836 0 338 0 66979 0 1132727547 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0.00 0.00 4.50 0.00 4.50 0.00 3 0 16.06 0.01 79.68 0.01 79.68 0.01

After:
05/11/2015 13:33 64536 19999 6.3 7.1 13.9 6.9 63932 21718 PTM 1723 4465 1687466 65713 0 0 80 0 653 4296 0 0.022 20 0 0 0 19915 0 0 0 0 2581416 836085 0 0 0 0 8 1 34 2342 32 31 12 1 0 0 0 0 4.3 21.1 32.2 0.0 11.3 26.6 41.3 4.3 20.2 31.3 0.0 13.3 26.4 41.3 7.2 7.0 7.1 0.0 6.3 6.3 6.3 -3.7 -22.3 6.5 0.0 11.3 7.8 7.1 Showtime 1 1 L0 17a ON ON No Showtime 16.4 0.0 243 237 1 1 0 42 10 16 0.1204 0.3781 16878 5374 0 0 0 0 9772737 0 354 0 0 0 0 104 81 48.00 0.00 0.00 3.98 0.00 0.00 0.01 64.22 45 1 VDSL2 0 0 0 0 0.00 0.00 0.00 0.00 0 0 2 0 1 0 18 0 8 0 1 0 0 0 G.INP 0 0 8 0 0 0 51 0 17 0 18 0 17 0 0 24 3 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 4918 0 0 0 0 0 0 0 48560 0 0 0 0 0 0 0 0 0 70090 0 0 0 28541 0 29 0 106327 0 37083 0 350 0 64532 0 1982031579 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0.00 0.00 4.50 0.00 4.50 0.00 3 0 16.06 0.01 79.68 0.01 79.68 0.01

Edit: here is the minute before. I just noticed that upstream attainable took a dive from 23409 to 16368 just before the resync.

05/11/2015 13:30 66999 19999 5.2 13.9 14.0 6.9 82260 23409 PTM 585 4381 1676002 44909 0 0 553502 0 0 61 0 153.751 283779 6813 61 0 4190330 0 0 701 0 3487496528 896168 3171568 0 0 0 16 1 12 2331 11 28 0 0 0 636796 15169 0 4.3 21.1 32.2 0.0 11.2 26.6 41.3 4.3 20.4 31.2 0.0 13.3 26.2 41.2 15.2 13.9 13.9 0.0 5.2 5.2 5.2 -3.4 -22.4 6.6 0.0 11.5 7.9 7.0 Showtime 1 1 L0 17a ON ON No Showtime 16.4 0.0 158 237 1 1 0 42 8 16 0.0754 0.3781 17724 5374 0 0 0 0 2595150125 0 1414375534 0 0 0 0 63 52 49.00 0.00 0.00 3.98 0.00 0.00 0.01 64.22 418346 960 VDSL2 52 0 0 0 0.00 0.00 0.00 0.00 0 0 1 0 0 0 10 0 0 0 0 0 0 0 G.INP 0 0 16 0 7 0 42 0 14 0 18 0 14 0 0 24 3 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 34458770 0 3736 0 0 0 0 0 344587081 0 3 0 0 0 0 0 0 0 70044 0 4 0 28486 0 4 0 41408 0 0 0 328 0 67020 0 1132674654 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0.00 0.00 4.50 0.00 4.50 0.00 3 0 16.06 0.01 79.68 0.01 79.68 0.01

Edited by kasg (Thu 05-Nov-15 20:09:11)

I've been getting weird things happening with my line where the downstream SNRM randomly jumps from 6dB to around 14dB for a couple of hours and returns to 6dB.

I resynced my router during one of these jumps and the downstream sync went up to just under 60 Mbps with a 10.5dB SNRM and a 74 Mbps max attainable. I also notice the QLN graph had dropped by around 10dBm/Hz across the board. Interestingly the max attainable is around what it used to be before I had a sudden 20 Mbps drop in sync 2 years ago which Openreach put down to deteriorating Cu/Al joints in the cable between the PCP and the DP I'm connected to.

In reply to a post by kasg:

Well that didn't last. After just under a week I had a resync at 13:31 today at 64536 (Reason: 1 Remote Defect Indicator/DLM) and my attainable is down to 63932 from 82488. I wonder what caused the jump and why has it reverted to where it was?

I'm not 100% convinced that you ever had a real attainable value that high. Generally, a high attainable value (compared to actual) only comes about because the actual SNRM is well above 6dB. My line has about 26Mbps "unused", which goes alongside an SNRM value of 12.5dB

It looks, to me, that the modem is mis-calculating the attainable, or mis-reporting the SNRM value.

In reply to a post by kasg:

If anyone is capable of interpreting the great long string from modem_stats.log:

Before:
05/11/2015 13:31 66999 19999 5.3 9.2 14.0 6.9 82488 16368 PTM 1070 4430 1683170 65154 0 0 553562 0 485 7168 0 153.767 290947 27058 7168 0 4205415 0 485 750 485 3490668080 1529473 3171552 0 0 0 16 1 22 2341 20 31 10 10 20245 633305 15085 0 4.3 21.1 32.2 0.0 11.2 26.6 41.3 4.3 21.2 32.1 0.0 13.3 26.2 41.2 10.6 8.0 9.7 0.0 5.6 5.3 5.0 -3.4 -22.4 6.6 0.0 11.5 7.9 7.0 Showtime 1 1 L0 17a ON ON No Showtime 16.4 0.0 158 237 1 1 0 42 8 16 0.0754 0.3781 17724 5374 0 0 0 0 2601818657 0 1414376953 0 0 0 0 63 52 49.00 0.00 0.00 3.98 0.00 0.00 0.01 64.22 418392 964 VDSL2 46 4 49 0 0.00 0.00 0.00 0.00 0 0 1 0 0 0 10 0 0 0 1 0 1 0 G.INP 0 0 16 0 7 0 42 0 14 0 18 0 14 0 0 24 3 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 34462505 0 3735 0 0 0 0 0 344624436 0 2596 0 2593 0 0 0 0 0 70090 0 46 0 28512 0 26 0 69244 0 27836 0 338 0 66979 0 1132727547 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0.00 0.00 4.50 0.00 4.50 0.00 3 0 16.06 0.01 79.68 0.01 79.68 0.01

After:
05/11/2015 13:33 64536 19999 6.3 7.1 13.9 6.9 63932 21718 PTM 1723 4465 1687466 65713 0 0 80 0 653 4296 0 0.022 20 0 0 0 19915 0 0 0 0 2581416 836085 0 0 0 0 8 1 34 2342 32 31 12 1 0 0 0 0 4.3 21.1 32.2 0.0 11.3 26.6 41.3 4.3 20.2 31.3 0.0 13.3 26.4 41.3 7.2 7.0 7.1 0.0 6.3 6.3 6.3 -3.7 -22.3 6.5 0.0 11.3 7.8 7.1 Showtime 1 1 L0 17a ON ON No Showtime 16.4 0.0 243 237 1 1 0 42 10 16 0.1204 0.3781 16878 5374 0 0 0 0 9772737 0 354 0 0 0 0 104 81 48.00 0.00 0.00 3.98 0.00 0.00 0.01 64.22 45 1 VDSL2 0 0 0 0 0.00 0.00 0.00 0.00 0 0 2 0 1 0 18 0 8 0 1 0 0 0 G.INP 0 0 8 0 0 0 51 0 17 0 18 0 17 0 0 24 3 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 4918 0 0 0 0 0 0 0 48560 0 0 0 0 0 0 0 0 0 70090 0 0 0 28541 0 29 0 106327 0 37083 0 350 0 64532 0 1982031579 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0.00 0.00 4.50 0.00 4.50 0.00 3 0 16.06 0.01 79.68 0.01 79.68 0.01

Edit: here is the minute before. I just noticed that upstream attainable took a dive from 23409 to 16368 just before the resync.

05/11/2015 13:30 66999 19999 5.2 13.9 14.0 6.9 82260 23409 PTM 585 4381 1676002 44909 0 0 553502 0 0 61 0 153.751 283779 6813 61 0 4190330 0 0 701 0 3487496528 896168 3171568 0 0 0 16 1 12 2331 11 28 0 0 0 636796 15169 0 4.3 21.1 32.2 0.0 11.2 26.6 41.3 4.3 20.4 31.2 0.0 13.3 26.2 41.2 15.2 13.9 13.9 0.0 5.2 5.2 5.2 -3.4 -22.4 6.6 0.0 11.5 7.9 7.0 Showtime 1 1 L0 17a ON ON No Showtime 16.4 0.0 158 237 1 1 0 42 8 16 0.0754 0.3781 17724 5374 0 0 0 0 2595150125 0 1414375534 0 0 0 0 63 52 49.00 0.00 0.00 3.98 0.00 0.00 0.01 64.22 418346 960 VDSL2 52 0 0 0 0.00 0.00 0.00 0.00 0 0 1 0 0 0 10 0 0 0 0 0 0 0 G.INP 0 0 16 0 7 0 42 0 14 0 18 0 14 0 0 24 3 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 34458770 0 3736 0 0 0 0 0 344587081 0 3 0 0 0 0 0 0 0 70044 0 4 0 28486 0 4 0 41408 0 0 0 328 0 67020 0 1132674654 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0.00 0.00 4.50 0.00 4.50 0.00 3 0 16.06 0.01 79.68 0.01 79.68 0.01

In time order, your downstream attainable speed goes
82260 -> 82488 -> 63932

meanwhile, downstream SNRM goes
5.2 -> 5.3 -> 6.3

Upstream, the same things are:
23409 -> 16368 -> 21718
13.9 -> 9.2 -> 7.1

On downstream, the attainable values just don't make sense with the comparable SNRM values. To really have an unused 15Mbps, you ought to have around 3-4dB spare SNRM, or a *lot* of bandwidth allocated to old-style FEC+interleaving.

On upstream, things seem even messier. There, it suggests funny things are happening on the line - perhaps noise.

On that front, I looked at the two graphs you posted originally. The most noticeable difference, to me, is the QLN graph. NB: This graph only shows what the noise environment looked like at the most recent re-sync, so doesn't change often.

The two QLN graphs show more than a 10dB difference in the noise environment (at the time of the syncs). The two SNRM graphs (with live values) show barely any difference, which suggests that the *live* noise environment is pretty similar.

Taken together, the difference in QLN but similarity in SNRM, suggests that the noise on your line can change significantly. The data isn't enough to say why this happens, or how often/regularly. That it does happen is something to consider.

Thanks very much for your analysis, but it did look to me that if I hadn't been banded at 66999 I would have synced at the maximum speed for those six days. Although the upstream SNRM diverged hugely for that period, the downstream SNRM seemed pretty stable and that was the one of most interest as I've always had maximum upstream sync anyway. It's not a problem, I'm perfectly happy with what I've got, but there did seem to be a few others that had reported strange things happening at about when I did.