I'm using a Zyxel VMG1312-B10D as supplied by Zen.

In reply to a post by Andrue:

In reply to a post by MrSaffron:

It has to remembered that xDSL modems will not drop the line to resync to a higher speed even if the data says its possible, they rely on something external doing this, i.e. usually a human.

DLM can force a resync to a higher speed as well, can't it?

Yes.

I always assumed that if you leave an FTTC modem alone it will generally end up at the 'right' speed anyway.

No. Only if DLM chooses to act one way or the another, which it doesn't necessarily do just for the sake of a difference we might find desirable but isn't really important. Like a couple of Mbps gain when we have 60Mbps already .

FWIW, I'm delighted with the speed I can have, this is just the novelty stage when I'm wanting to optimise and get the best out of what I can get.

A few meg here or there won't really matter, right now I can stream a few HD channels downstairs while downloading big files and working. But if I was missing something easy to fix, then I'd obviously want to do it.

Actual speed now matching attainable, apparently. So the speed will it seems creep up again.

Text

1 23 45 67 89 1011 1213 1415 1617 1819 2021 2223 2425

============================================================================     VDSL Training Status:   Showtime                    Mode:   VDSL2 Annex B             VDSL Profile:   Profile 17a            Traffic Type:   PTM Mode              Link Uptime:   0 day: 2 hours: 4 minutes============================================================================        VDSL Port Details       Upstream         Downstream               Line Rate:     18.186 Mbps       63.261 Mbps     Actual Net Data Rate:     18.155 Mbps       63.262 Mbps          Trellis Coding:         ON                ON               SNR Margin:        6.1 dB            6.0 dB            Actual Delay:          0 ms              0 ms           Transmit Power:        7.6 dBm          13.1 dBm           Receive Power:       -7.3 dBm         123.3 dBm               Actual INP:        0.0 symbols      52.0 symbols       Total Attenuation:       15.0 dB          4294967186.4294967294 dB Attainable Net Data Rate:     18.076 Mbps       63.436 Mbps============================================================================       VDSL Band Status    U0      U1      U2      U3      D1      D2      D3  Line Attenuation(dB):  8.0    32.8    48.6     N/A    14.5    37.9    57.8   Signal Attenuation(dB):  8.0    32.4    48.0     N/A    21.6    37.8   -116.9           SNR Margin(dB):  5.7     6.1     6.1     N/A     5.9     5.9     6.1      Transmit Power(dBm):  0.6   -10.7     6.6     N/A    10.0     7.8     6.4   ============================================================================

Interleaving has been turned off. DLM resync's the line when it does that. Actual rises, attainable falls. We don't know why attainable falls, but it's normal. And vice versa.

@Irby

In the variety of stats you have given us, look at the progression of two values in particular - neither of which is the speed.

Check downstream "actual delay" and "Actual INP".

Original install: unknown
Fri 10:39: delay=12ms, INP=4 symbols
Fri 13:21: delay=13ms, INP=4 symbols
Sun 09:28: delay=0ms, INP=52 symbols

In the first two readings, you are on an interleaved profile - and both the delay (of 12ms) and INP (of 4 symbols) are higher than standard DLM intervention used to be.

If, when you were originally installed, you were on a free profile, it would be easy to understand a loss of 10Mbps (edit: of /actual/ line speed) being down to DLM intervention. Do you have any data from the initial installation, rather than just /after/ the loss of attainable speed? And what happened to /actual/ speed over that time?

NB: Once DLM has intervened to turn on old-style FEC+interleaving, you lose some of your /actual/ sync speed, but modems then seem to report a higher /attainable/ speed. The difference is accounted for by the extra parity data being transmitted to provide error correction ... but the lesson to be learnt is that the attainable can never be fully attained when DLM relents. Quoting the /actual/ speed helps more.

In a case like this, where DLM appears to have intervened, and intervened quite heavily, the statistics that you need to monitor are the ones with all the error information - the FEC count, the CRC count, the ES count, the retransmission counter, the retransmission failure counter, and the LEFTRS counter.

Whatever has happened with the error counters, however, DLM has now decided to remove the heavy FEC+interleaving and turn on G.INP on your line (the latest INP value of 40+ seems to signify this). This has returned 10Mbps of actual speed.

The activation of G.INP after 48 hours is a fairly standard step for DLM these days.

In reply to a post by Irby:

I'm using a Zyxel VMG1312-B10D as supplied by Zen.

If you want to monitor the line statistics, I believe this modem is supported by DSLstats:
http://forum.kitz.co.uk/index.php/board,46.0.html

That would also allow the stats to be uploaded to MyDslWebStats.

Edited by deleted (Sun 22-May-16 11:04:03)

Thanks for the detailed reply, really anything over 50mbps is just gravy