Opinion on these FTTC stats please

Hi All,

May I please have an opinion on these FTTC stats from an HG612 modem. The reason why I'm asking, when I first switched from 6Mbit ADSL2+ to FTTC I got a max download speed around 120Mbit, with SNR of some 26dB. I was almost certainly one of the first people to go FTTC in the area. I've paced out distance to the cabinet at 120 meters. I know the route as I've had 3 REIN issues over the past 5 years (dodgy sat RX power supply, dodgy Sky+ box & a very dodgy ADSL modem/router wall-wart PSU all causing lots of stress to their owners and to me trying to track it down)

I don't have any stability problems, line up for months at a time, but I'm toying with going 80/20 rather than 40/10 and as it currently stands it doesn't look like I'd get the 80...and being so close I'm curious why.

Thanks,

Kevin

PS: Modem got rebooted this morning after a firmware upgrade, the stats so far look very typical of the before upgrade stats.

xdslcmd info --stats
xdslcmd: ADSL driver and PHY status
Status: Showtime
Retrain Reason: 0
Last initialization procedure status: 0
Max: Upstream rate = 26328 Kbps, Downstream rate = 76256 Kbps
Bearer: 0, Upstream rate = 9999 Kbps, Downstream rate = 39998 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): 17.9 22.1
Attn(dB): 7.3 0.0
Pwr(dBm): 13.8 -9.3
VDSL2 framing
Bearer 0
MSGc: 26 58
B: 237 236
M: 1 1
T: 64 23
R: 16 16
S: 0.1893 0.7543
L: 10736 2694
D: 1 1
I: 254 127
N: 254 254
Counters
Bearer 0
OHF: 8338417 988471
OHFErr: 41 46
RS: 533637651 1282370
RSCorr: 8 42
RSUnCorr: 230 0

Bearer 0
HEC: 382 0
OCD: 13 0
LCD: 13 0
Total Cells: 1949765602 0
Data Cells: 13852322 0
Drop Cells: 0
Bit Errors: 0 0

ES: 38 44
SES: 0 0
UAS: 24 24
AS: 25351

Bearer 0
INP: 0.00 0.00
INPRein: 0.00 0.00
delay: 0 0
PER: 3.04 8.70
OR: 84.20 58.79
AgR: 40082.29 10057.90

Bitswap: 3432/3432 2/2

Total time = 7 hours 2 min 55 sec
FEC: 8 42
CRC: 41 46
ES: 38 44
SES: 0 0
UAS: 24 24
LOS: 0 0
LOF: 0 0
LOM: 0 0
Latest 15 minutes time = 2 min 55 sec
FEC: 0 2
CRC: 0 1
ES: 0 1
SES: 0 0
UAS: 0 0
LOS: 0 0
LOF: 0 0
LOM: 0 0
Previous 15 minutes time = 15 min 0 sec
FEC: 1 4
CRC: 2 2
ES: 2 2
SES: 0 0
UAS: 0 0
LOS: 0 0
LOF: 0 0
LOM: 0 0
Latest 1 day time = 7 hours 2 min 55 sec
FEC: 8 42
CRC: 41 46
ES: 38 44
SES: 0 0
UAS: 24 24
LOS: 0 0
LOF: 0 0
LOM: 0 0
Previous 1 day time = 0 sec
FEC: 0 0
CRC: 0 0
ES: 0 0
SES: 0 0
UAS: 0 0
LOS: 0 0
LOF: 0 0
LOM: 0 0
Since Link time = 7 hours 2 min 29 sec
FEC: 8 42
CRC: 41 46
ES: 38 44
SES: 0 0
UAS: 0 0
LOS: 0 0
LOF: 0 0
LOM: 0 0
#
xdslcmd info --pbParams
xdslcmd: ADSL driver and PHY status
Status: Showtime
Retrain Reason: 0
Last initialization procedure status: 0
Max: Upstream rate = 26237 Kbps, Downstream rate = 76256 Kbps
Bearer: 0, Upstream rate = 9999 Kbps, Downstream rate = 39998 Kbps

Discovery Phase (Initial) Band Plan
US: (7,32) (871,1205) (1972,2782)
DS: (33,859) (1216,1961) (2793,3970)
Medley Phase (Final) Band Plan
US: (7,32) (871,1205) (1972,2782)
DS: (33,859) (1216,1961) (2793,3970)
VDSL Port Details Upstream Downstream
Attainable Net Data Rate: 26237 kbps 76256 kbps
Actual Aggregate Tx Power: - 9.2 dBm 13.8 dBm
====================================================================================
VDSL Band Status U0 U1 U2 U3 U4 D1 D2 D3
Line Attenuation(dB): 2.1 7.5 10.6 N/A N/A 4.0 8.1 12.5
Signal Attenuation(dB): 2.1 6.7 9.8 N/A N/A 4.7 8.0 12.5
SNR Margin(dB): 22.2 21.9 22.1 N/A N/A 17.9 17.9 17.9
TX Power(dBm): 23.5 36.4 9.5 N/A N/A 11.2 8.2 6.5
#

Edited by deleted (Wed 18-Feb-15 16:56:08)

Hello Kevin

That "max download speed around 120Mbit" I think is the maximum obtainable speed that you could get on your line at that time, not that you would get it.

But looking now its Max: Upstream rate = 26328 Kbps, Downstream rate = 76256 Kbps.
So upgrading should get you close to these new speeds, apart from your upstream will drop to around 19999 Kbps (20Mbps)
The reason your max obtainable speeds has decreased is more people on your cabinet getting fibre.

Paul

In reply to a post by PaulKirby:

Hello Kevin

That "max download speed around 120Mbit" I think is the maximum obtainable speed that you could get on your line at that time, not that you would get it.

But looking now its Max: Upstream rate = 26328 Kbps, Downstream rate = 76256 Kbps.
So upgrading should get you close to these new speeds, apart from your upstream will drop to around 19999 Kbps (20Mbps)
The reason your max obtainable speeds has decreased is more people on your cabinet getting fibre.

Paul

The current Upstream is only 9999 - capped. 26328 in the Max Attainable so moving to an 80/20 product would give 76xxx & 19999 Sync rates.

In reply to a post by MHC:

The current Upstream is only 9999 - capped. 26328 in the Max Attainable so moving to an 80/20 product would give 76xxx & 19999 Sync rates.

Wasn't that what I said?

I wasn't referring to his current sync speed.

Paul

In reply to a post by PaulKirby:

In reply to a post by MHC:

The current Upstream is only 9999 - capped. 26328 in the Max Attainable so moving to an 80/20 product would give 76xxx & 19999 Sync rates.

Wasn't that what I said?

I wasn't referring to his current sync speed.

Paul

No, how could his upstream drop to 19999 from 9999? It will rise to and be capped at 19999.

In reply to a post by PaulKirby:

So upgrading should get you close to these new speeds, apart from your upstream will drop to around 19999 Kbps (20Mbps)

Who said anything about 9999Kbps?

I said Max: Upstream rate = 26328 Kbps, Downstream rate = 76256 Kbps so that upstream of 26328 Kbps will be reduced to 19999Kbps.

Paul

So the considered opinion so far is that a drop from max 120Mbit 26db SNR (and presumably very few FTTC neighbours) to 76Mbit 18dB SNR is down to crosstalk rather than any low level line fault?

Most likely cause

The OP stated his Upstream is currently 9999

No you actually posted: upstream will drop to around 19999 Kbps (20Mbps)

In reply to a post by MHC:

The OP stated his Upstream is currently 9999

No you actually posted: upstream will drop to around 19999 Kbps (20Mbps)

Well the OP said that they was getting a speed of 120Mbps where I said that was the max obtainable speed for their line, and I was still referring to that max obtainable speed that they are still getting (not their sync speed) i.e.

But looking now its Max: Upstream rate = 26328 Kbps, Downstream rate = 76256 Kbps.

I was never referring to their current sync speed.
And the OP never said anything about the upstream, their sync upstream granted is in their posted stats, but they never spoke about that, it was more about their downstream.

If I was referring to they current sync speed I would of said it would of gone up.

Maybe I should of said if upgrading to the 80/20 option their upload speed would drop from 26328 Kbps (max obtainable speed) to 19999 Kbps (i.e. capped), I assumed people would of realised that I was still referring to the max obtainable speed that they can get from their connection to the fibre cabinet and not their current sync speed.

Paul

Edited by PaulKirby (Wed 18-Feb-15 18:36:23)

Im supprised that with SNR of 17.9 and Attenuation of 7.3 max is only 76. Shouldf be much higher no? On my line with SNr of 12.3 and Attn of 10 my max is 103 Mb, so in my opinon your max should be above 100 Mb.

My stats:
xdslcmd info --stats
xdslcmd: ADSL driver and PHY status
Status: Showtime
Retrain Reason: 0
Last initialization procedure status: 0
Max: Upstream rate = 36188 Kbps, Downstream rate = 102044 Kbps
Bearer: 0, Upstream rate = 19999 Kbps, Downstream rate = 79987 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): 12.4 23.1
Attn(dB): 10.0 0.0
Pwr(dBm): 12.8 -4.6

so your line stats are better then mine and still lower values...

Edited by deleted (Wed 18-Feb-15 19:01:19)

MHC is right and I am afraid you aren't.

You stated that the upstream would drop to 19999. The work "drop" is wrong:

Either, the sync will increase from 9999 to 19999

or

The max attainable will continue to be 26328 (ish)

Neither of these will drop by going from 40/10 to 80/20.

Theoretical question:

If the line was getting such high max rates is it possible that it has dialled back the power? By dialling back the power could this impact on the accuracy of the "guess" at max sync attainable?

This is a possibility too

At the end of the day the only way to know is to try and run the line at the faster speeds

In reply to a post by MrSaffron:

This is a possibility too

At the end of the day the only way to know is to try and run the line at the faster speeds

That's certainly a thought. And I see no point in a modem shouting when it has no need, it does no favours for crosstalk.

Thanks for everyone's contributions...I knew what you all meant

The OP has current sync speeds of 40/10 (capped by choice of package) while yours is 80/20.

The extra spare SNR (12dB) for him will give him an extra 36Mbps, while your spare SNR (6dB) will give you 20Mbps.

I note from you line profile that DLM has not intervened (INP=0.0 and delay=0), yet the modems have negotiated to turn FEC protection on, but without interleaving - in both upstream & downstream directions.

This protection is using 16 bytes out of every 255 bytes as the FEC protection overhead - which means it is using around 6% of your bandwisth.

I don't know whether that would give you the extra 2.5Mbps on top of the attainable if you switched package; when DLM intervenes, that attainable figure becomes less trustworthy - so I don't know whether it would be wrong here too.

From the error stats, it doesn't look like the downstream FEC protection is working too well, nor that it is particularly needed.