Can someone please explain "Max" rate to me?

Evening,

Is anyone able to explain the "Max" quoted below? Should I be syncing closer to 49mbit than I am at present? My ISP is telling me my line is running as fast as it can and I have no reason to doubt them at all, im just trying to understand what this "Max" rate actually means.

Also in regards to the dslstats dump below, am I likely to be able to be rid of my interleaving given the amount of errors on my line after a few weeks? Still getting my head around the CRC/ES figures displayed!

adsl info --stats
adsl: ADSL driver and PHY status
Status: Showtime
Last Retrain Reason: 0
Last initialization procedure status: 0
Max: Upstream rate = 8577 Kbps, Downstream rate = 49615 Kbps
Bearer: 0, Upstream rate = 8420 Kbps, Downstream rate = 40691 Kbps

Link Power State: L0
Mode: VDSL2 Annex B
VDSL2 Profile: Profile 17a
TPS-TC: PTM Mode(0x0)
Trellis: U:ON /D:ON
Line Status: No Defect
Training Status: Showtime
Down Up
SNR (dB): 6.4 6.1
Attn(dB): 24.3 0.0
Pwr(dBm): 11.8 4.0

VDSL2 framing
Bearer 0
MSGc: 18 28
B: 51 238
M: 1 1
T: 64 30
R: 12 16
S: 0.0407 0.9027
L: 12592 2260
D: 797 1
I: 64 255
N: 64 255

Counters
Bearer 0
OHF: 131094445 512661
OHFErr: 2450 65
RS: 3495309746 1428775
RSCorr: 19047941 192
RSUnCorr: 141575 0

Bearer 0
HEC: 32123 0
OCD: 12 0
LCD: 12 0
Total Cells: 1029900545 0
Data Cells: 928282293 0
Drop Cells: 0
Bit Errors: 0 0

ES: 538 64
SES: 0 0
UAS: 24 24
AS: 342475

Bearer 0
INP: 3.00 0.00
INPRein: 0.00 0.00
delay: 8 0
PER: 2.61 13.59
OR: 73.49 20.01
AgR: 40764.76 8439.81

Bitswap: 153473/153478 75/78

Total time = 3 days 23 hours 8 min 31 sec
FEC: 19047941 192
CRC: 2450 65
ES: 538 64
SES: 0 0
UAS: 24 24
LOS: 0 0
LOF: 0 0
LOM: 0 0
Latest 15 minutes time = 8 min 31 sec
FEC: 17693 0
CRC: 11 0
ES: 3 0
SES: 0 0
UAS: 0 0
LOS: 0 0
LOF: 0 0
LOM: 0 0
Previous 15 minutes time = 15 min 0 sec
FEC: 28805 0
CRC: 3 0
ES: 1 0
SES: 0 0
UAS: 0 0
LOS: 0 0
LOF: 0 0
LOM: 0 0
Latest 1 day time = 23 hours 8 min 31 sec
FEC: 1895099 43
CRC: 580 13
ES: 144 13
SES: 0 0
UAS: 0 0
LOS: 0 0
LOF: 0 0
LOM: 0 0
Previous 1 day time = 24 hours 0 sec
FEC: 2381660 58
CRC: 742 21
ES: 119 21
SES: 0 0
UAS: 0 0
LOS: 0 0
LOF: 0 0
LOM: 0 0
Since Link time = 3 days 23 hours 8 min 5 sec
FEC: 19047941 192
CRC: 2450 65
ES: 538 64
SES: 0 0
UAS: 0 0
LOS: 0 0
LOF: 0 0
LOM: 0 0
>

Are you only on a 40mb package? Or 80mb?

looks to me like you on the 40meg package but your line is capable of getting 49meg.

Theres probably no point in upgrading to the 70meg product as you'll probably only get a little more speed and it'll cost more.

So you COULD pay extra to get on to the 70meg package and perhaps get a little more speed but its not really worth it.

Up to 80mbit yes, I think this is confirmed from the dslstats dump as im on a 17a profile.

All products are on 17a including 40/10 and 80/20

"Max" rate is usually the rate would expect to get with the current signal quality at your target snr.
Very roughly, the snr is the amount of 'extra' signal needed to cover noise problems.
The target snr is almost always 6db. That is the snr it tries to get when it makes a connection.
If you have a higher snr, that means more stability but slower speeds.

The stats when you took them show 6.4 snr downstream; the line must have been a little better then than when the previous connection was made.
If the line is periodically noisy, it is most likely to lose connection when the noise is high.
When it tries to reconnect it is doing it with a bad signal, so the connection will be on the slow side.
You can force a reconnection when the signal is good to get best speed and you should get a lot closer to your 49Mbps;
but that runs a significant risk of broken connection during the next noisy period (and reconnection back nearer 40Mbps).

When I am talking connection here, that is the connection between the modem and the cabinet; not the higher level one from router into the internet.

Whatever you do, don't force a reconnection for the modem by unplugging and replugging the phone connection.
If possible, disconnect/reconnect via the modem interface, if not by power down, wait a bit, and power up.
Any disconnect/reconnect may be mistinterpreted by DLM as noise, which will keep you on interleaved for longer.

I'm not sure what levels of errors trigger interleaving so can't help you on that one.
Once DLM does introduce interleaving, it can take three weeks or so before it removes it even if the line is near perfect.

I'm guessing that you are on a 40/10 package from those stats as it isn't normal to have such a big gap between the maximum achievable and actual data rate as you have downstream. It's normally a lot smaller, as you have on the upstream.

Anyway, to explain the difference, The maximum data rate is that which would could be achieved on your line with the target SNR margin (which will be 6dB) and without error correction overheads. As a certain amount of the bandwidth will be used for error correction (the actual amount varies according to the measures taken), the actual data sync rate will always be less than the maximum achievable. However, it's normally only the odd 100kbps or two (like your upstream rate), so I can only explain the 9mbps or so difference on downstream by concluding that you are on a 40mbps service. In that case, it will never sync faster than 40mbps (the exact number of kbps depends on some fairly arcane definitions of what the units actually mean; for strange reasons lost in the history of telecoms, 1 mbps is neither 1000 x 1000 bps or 1024 x 1024 bps, but a strange mix).

Another point that's worth mentioning is your modem is actually mislabeling what is more accurately called the "noise margin" or "SNR margin" as SNR.

Briefly, the SNR is limited by the electrical characteristics of your line and the amount of power put out be the modems at each end. As the latter has defined maximums and, if you've sorted out any domestic wiring, you can't change the electrical characteristics of your line (that is noise, attenuation, balance etc), then SNR is effectively fixed. A given SNR can achieve a particular data rate for a given modulation scheme (in this case VDSL2 with a particular frequence and spectral power plan). However, to try and sync at that speed would ask for trouble as it would constantly drop out of sync. So there will be a defined "SNR margin", which is essentially a "safety margin". It's usually defined at the cabinet end, most usually at 6dB and the line sync at the maximum rate it can achieve with the given margin and error correction overheads subject to any caps (like 40mbps).

That's why on poor quality lines with lots of dropouts and noise variation a higher margin will be set, but this will result in a lower sync rate.

17a doesn't define what package you are on. It's largely just a definition of the frequency profiles, carrier frequency allocations, power and so on (even then subject to local power masking).

TheEulerId is nearly right...

The Max Attainable speed is an estimate of what speed you would get at the target SNR (6dB), and the estimate is the raw bandwidth BEFORE any error correction overhead is taken off.

The error correction overhead is normally zero, unless DLM has intervened.

What @TheEulerId missed is that DLM intervention *has* happened here, as can be seen with an INP value of 3 and a "delay" of 8; this causes FEC and Interleaving to be turned on.

The actual overhead used by FEC and Interleaving is negotiated by the modems, and in this case has resulted in (R=12) bytes out of every (N=64) bytes as overhead - or around 19% of the bandwidth.

That overhead is the difference between the actual and attainable figures.

But there's more...

These statistics look like they have come from a Huawei HG612 modem; this modem shows a strange quirk in the display of the Max Attainable figure, when DLM has intervened. If DLM were removed, the max attainable figure would drop by around half of the amount it is above the actual figure, and the actual speed would increase by about half. In your case they'd meet at around 45Mbps.

Cheers guys.

FYI the stats are actually from a Billion 8100nl.

Perhaps the ISP are correct in saying 40mbit is the max for my line from what you're saying then Wombat?