50mb Upload Speed Appauling!

[StumpyBloke]

Hi guys,

Newbie here so hi to all first-off!

I have had the 50mb service for the last few months but recently my upload speed has dropped to around 600kbps. I used to get over 1.5mbps. I have now had 2 visits and each time I phoned them up they said the voltage was too high at the modem. Today the engineer added an attenuator to lower the voltage but the upload speed it still rubbish. It has been like this for weeks and weeks.

I was given the usual guff that the posible 1.5mbps speed is only "up to" to which I replied is ****!! Surely to god I should be able to get a better speed than this???!!! I am so sick of being given the run-around!!

My download speed normally comes back at about 50000kbps. I dont know if this makes any difference but I am in the ST15 postcode (Staffordshire).

Any advice appreciated.

TIA, Rich

[Ignitionnet]

What are you uploading to to get that result sir?

You wouldn't be able to get the full 50Mbit download speed if your up were that low.

[Sephiroth]

Also I'm puzzled as to why an attenuator would need to be fitted for upload power? BBings will correct me quickly where I might be wrong, but upstream power is determined by the CMTS based in its SNR estimate. If an upstream attenuator is fitted, I'd expect the CMTS to continue to raise the upstream power to combat whatever noise is on the circuit and if none (now) to overcome the attenuator.

[StumpyBloke]

BB, I am using www.mybroadbandspeed.co.uk and www.speedtest.net, oh and also tried a bittorrent. They all max out at about the same figure.

Sephiroth - I dont understand all this stuff, all I know is it was perfect when first installed and its been useless for ages.

Latest results from mybroadbandspeed.co.uk - 50365kbps download and 630kbps upload.

Thanks for your replies guys.

Rich

[Ignitionnet]

Also I'm puzzled as to why an attenuator would need to be fitted for upload power? BBings will correct me quickly where I might be wrong, but upstream power is determined by the CMTS based in its SNR estimate. If an upstream attenuator is fitted, I'd expect the CMTS to continue to raise the upstream power to combat whatever noise is on the circuit and if none (now) to overcome the attenuator.

SNR no, CMTS tells modem to raise power to reach target received power. SNR only becomes an issue when it's so bad CMTS doesn't 'hear' modem, then it'll tell it to raise power as it assumes Tx power is too low.

Attenuator probably not for upstream.

I'll pass on commenting on the below in full beyond that the CMTS doesn't react to SNR conditions downstream, it has no visibility of unless asked to poll modems and won't change downstream modulation in response to modems in strife.

[Sephiroth]

A primer (I hope).

It's all suitably complex. You have a two way circuit from your perspective.

Downstream power is needed to send data TO you from the server (CMTS). Upstream power is needed to send data to the cable modem FROM the CMTS.

The CMTS controls everything. It sends out its data at a fixed power value of 50 dBmv (I won't explain the realtive power values here), calculated in theory to arrive at your modem with 0 dBmv (which represents a nominal power of, I think, 75 milliwatts - BBings will jump on this if I'm wrong). The cable modem is designed to work with lower or higher power levels because the path to the modem is not ideal; it may be nearer to or further from the street box, for example. IMO (and others have their own view) a range -3 dBmv to +6 dBmv is unlikely to cause problems. Too much power brings too much noise.

The cable modem estimates the signal to noise ratio (SNR) based on what it has demodulated with/without errors. This is presented in the modem stats. For reasons too complex to explain in this primer, the data density used in your downstream (256QAM!) needs the SNR to be higher than 30 dB at all costs; > 33 dB to handle effects at the margin and 35 dB to be on the safe side. The CMTS can only react to a poor SNR by lowering the modulation to 64QAM which has a lower low SNR threshold.

In the other direction, the CMTS estimates the SNR on the route from the cable modem based on initial ranging requests. It then commands the cable modem as to the power level needed to overcome the estimated noise impairment. The CMTS does this very frequently so as to maintain its upstream circuit and only when it fails does the modem event log report something. The cable modem maxes out at 58 or 61 dBmv depending on model. If you're over 55 dBmv upstream, there's a struggle to get data to the CMTS.

The potential causes of upstream impairments are many - from loosely screwed in coax in the home or on the other side of the wall, through RF noise ingress due to corrosion (dipole effect), badd connexions in the street box, failing laser, noise reflection - it's amazing it works at all because so much of the circuit is copper and modulators/demodulators, combiners and so on.

I might have misunderstood what he's fitted by way of an attenuator. He would have fitted a forward path attenuator to lower downstream power output - possibly because you're close to the streetbox and possibly connected to the wrong attenuation block in the street box.

After all that spiel above, perhaps you could pst your modem stats so we can attempt to judge what's going on, plus the event log REMOVING ANY CM-MAC ADDRESS INFORMATION.

HTH.

[StumpyBloke]

Hi, hopefully this is the info you need...

Cable Modem Information
Cable Modem : DOCSIS 1.0/1.1/2.0/3.0 Compliant
Serial Number : xxxxxxxxxxxxxxxxxxxxxxxx
Boot Code Version : 6.1.1c
Software Version : 3.11.1011
Hardware Version : 1.39
CA Key : Installed


Cable Modem Status
Item Status Comments
Acquired Downstream Channel 434.250000 MHz Primary Downstream Locked
Ranged Upstream Channel 47.400002 MHz Success
Provisioning State OK Operational
Ethernet Link Status Up 100 Mbps/Full duplex


Cable Modem Downstream
DS-1 DS-2 DS-3 DS-4
Frequency 434250000 442250000 450250000 458250000
Lock Status
(QAM Lock/FEC Sync/
MPEG Lock) Y/Y/Y Y/Y/Y Y/Y/Y Y/Y/Y
Channel Id 1 2 3 4
Modulation 64QAM 64QAM 64QAM 64QAM
Symbol Rate
(Msym/sec) 6.952 6.952 6.952 6.952
Interleave Depth I=12 I=12 I=12 I=12
J=17 J=17 J=17 J=17
Power Level
(dBmV) 4.62 4.53 4.39 4.78
RxMER
(dB) 35.54 35.20 34.87 35.37
Correctable
Codewords 3482 37446 82695 30960
Uncorrectable
Codewords 252 773 731 242


Cable Modem Upstream
US-1 US-2 US-3 US-4
Channel Type 1.0 N/A N/A N/A
Channel ID 3 N/A N/A N/A
Frequency
(Hz) 47400000 N/A N/A N/A
Ranging Status Success N/A N/A N/A
Modulation 16QAM N/A N/A N/A
Symbol Rate
(KSym/sec) 2560 N/A N/A N/A
Mini-Slot Size 2 N/A N/A N/A
Power Level
(dBmV) 39.25 N/A N/A N/A
T1 Timeouts 0
T2 Timeouts 0 0 0 0
T3 Timeouts 0 0 0 0
T4 Timeouts 0 0 0 0


Cable Modem Upstream Burst
US-1
Req
Init Maint
Per Maint
Short Data
Long Data

(1)
(3)
(4)
(5)
(6)



Modulation Type QPSK QPSK QPSK 16QAM 16QAM

Differential Encoding OFF OFF OFF OFF OFF
Preamble Length 64 128 128 144 160
Preamble Value Offset 140 6 6 216 216
FEC Error Correction (T) 0 5 5 5 10
FEC Codeword Information Bytes (k) 16 34 34 78 235
Maximum Burst Size 2 0 0 8 0
Guard Time Size 8 48 48 8 8
Last Codeword Length FIX FIX FIX SHORT SHORT
Scrambler on/off ON ON ON ON ON


Cable Modem Operation Configuration
General Configuration
Network Access : Allowed
Maximum Number of CPEs : 1
Baseline Privacy : Enabled
DOCSIS Mode : DOCSIS 3.0
Config File : Pcaa1a92007a50b13.cm
Primary Downstream Service Flow
SFID : 6657
Max Traffic Rate : 53000000 bps
Max Traffic Burst : 10000 bytes
Min Traffic Rate : 0 bps
Primary Upstream Service Flow
SFID : 6656
Max Traffic Rate : 1750000 bps
Max Traffic Burst : 1600 bytes
Min Traffic Rate : 0 bps
Max Concatenated Burst : 0 bytes
Scheduling Type : Best Effort


Cable Modem Event Log
First Time Last Time Priority Description
Wed Jan 20 00:46:30 2010 Wed Jan 20 00:46:30 2010 Critical (3) Unicast Maintenance Ranging attempted - No response - Retries exhausted;CM-MAC=xx:xx:xx:xx:xx:xx;CMTS-MAC=ff:ff:ff:ff:ff:ff:ff;CM-QOS=1.1;CM-VER=3.0;
Wed Jan 20 00:46:35 2010 Wed Jan 20 00:46:41 2010 Critical (3) No Ranging Response received - T3 time-out;CM-MAC=xx:xx:xx:xx:xx:xx;CMTS-MAC=ff:ff:ff:ff:ff:ff:ff;CM-QOS=1.1;CM-VER=3.0;
Wed Jan 20 00:46:42 2010 Wed Jan 20 00:46:42 2010 Warning (5) B-INIT-RNG Failure - Retries exceeded;CM-MAC=xx:xx:xx:xx:xx:xx;CMTS-MAC=ff:ff:ff:ff:ff:ff:ff;CM-QOS=1.1;CM-VER=3.0;
Wed Jan 20 00:46:53 2010 Thu Jan 21 04:18:46 2010 Critical (3) No Ranging Response received - T3 time-out;CM-MAC=xx:xx:xx:xx:xx:xx;CMTS-MAC=ff:ff:ff:ff:ff:ff:ff;CM-QOS=1.1;CM-VER=3.0;
Thu Jan 21 04:18:48 2010 Thu Jan 21 04:18:48 2010 Critical (3) Ranging Request Retries exausted;CM-MAC=xx:xx:xx:xx:xx:xx;CMTS-MAC=ff:ff:ff:ff:ff:ff:ff;CM-QOS=1.1;CM-VER=3.0;
Thu Jan 21 04:18:48 2010 Thu Jan 21 04:18:48 2010 Critical (3) Unicast Maintenance Ranging attempted - No response - Retries exhausted;CM-MAC=xx:xx:xx:xx:xx:xx;CMTS-MAC=ff:ff:ff:ff:ff:ff:ff;CM-QOS=1.1;CM-VER=3.0;
Thu Jan 21 04:18:56 2010 Thu Jan 21 04:19:02 2010 Critical (3) No Ranging Response received - T3 time-out;CM-MAC=xx:xx:xx:xx:xx:xx;CMTS-MAC=ff:ff:ff:ff:ff:ff:ff;CM-QOS=1.1;CM-VER=3.0;
Thu Jan 21 04:19:03 2010 Thu Jan 21 04:19:03 2010 Warning (5) B-INIT-RNG Failure - Retries exceeded;CM-MAC=xx:xx:xx:xx:xx:xx;CMTS-MAC=ff:ff:ff:ff:ff:ff:ff;CM-QOS=1.1;CM-VER=3.0;
Thu Jan 21 04:19:13 2010 Fri Jan 22 19:51:55 2010 Critical (3) No Ranging Response received - T3 time-out;CM-MAC=xx:xx:xx:xx:xx:xx;CMTS-MAC=ff:ff:ff:ff:ff:ff:ff;CM-QOS=1.1;CM-VER=3.0;
Fri Jan 22 21:50:29 2010 Sat Jan 23 17:57:07 2010 Warning (5) TEK Invalid - Invalid Key Sequence Number;CM-MAC=xx:xx:xx:xx:xx:xx;CMTS-MAC=ff:ff:ff:ff:ff:ff:ff;CM-QOS=1.1;CM-VER=3.0;
Sat Jan 23 19:19:37 2010 Sun Jan 24 19:38:09 2010 Critical (3) No Ranging Response received - T3 time-out;CM-MAC=xx:xx:xx:xx:xx:xx;CMTS-MAC=ff:ff:ff:ff:ff:ff:ff;CM-QOS=1.1;CM-VER=3.0;
Sun Jan 24 20:56:20 2010 Sun Jan 24 20:56:20 2010 Warning (5) TEK Invalid - Invalid Key Sequence Number;CM-MAC=xx:xx:xx:xx:xx:xx;CMTS-MAC=ff:ff:ff:ff:ff:ff:ff;CM-QOS=1.1;CM-VER=3.0;
Sun Jan 24 22:40:32 2010 Mon Jan 25 20:17:55 2010 Critical (3) No Ranging Response received - T3 time-out;CM-MAC=xx:xx:xx:xx:xx:xx;CMTS-MAC=ff:ff:ff:ff:ff:ff:ff;CM-QOS=1.1;CM-VER=3.0;
Tue Jan 26 20:15:07 2010 Tue Jan 26 21:58:33 2010 Warning (5) TEK Invalid - Invalid Key Sequence Number;CM-MAC=xx:xx:xx:xx:xx:xx;CMTS-MAC=ff:ff:ff:ff:ff:ff:ff;CM-QOS=1.1;CM-VER=3.0;
Wed Jan 27 07:47:45 2010 Wed Jan 27 07:47:45 2010 Critical (3) No Ranging Response received - T3 time-out;CM-MAC=xx:xx:xx:xx:xx:xx;CMTS-MAC=ff:ff:ff:ff:ff:ff:ff;CM-QOS=1.1;CM-VER=3.0;
Thu Jan 28 00:21:35 2010 Thu Jan 28 00:21:35 2010 Warning (5) TEK Invalid - Invalid Key Sequence Number;CM-MAC=xx:xx:xx:xx:xx:xx;CMTS-MAC=ff:ff:ff:ff:ff:ff:ff;CM-QOS=1.1;CM-VER=3.0;
Fri Jan 29 12:38:07 2010 Fri Jan 29 12:38:35 2010 Critical (3) No Ranging Response received - T3 time-out;CM-MAC=xx:xx:xx:xx:xx:xx;CMTS-MAC=ff:ff:ff:ff:ff:ff:ff;CM-QOS=1.1;CM-VER=3.0;
Fri Jan 29 12:38:38 2010 Fri Jan 29 12:38:38 2010 Critical (3) Ranging Request Retries exausted;CM-MAC=xx:xx:xx:xx:xx:xx;CMTS-MAC=ff:ff:ff:ff:ff:ff:ff;CM-QOS=1.1;CM-VER=3.0;
Fri Jan 29 12:38:38 2010 Fri Jan 29 12:38:38 2010 Critical (3) Unicast Maintenance Ranging attempted - No response - Retries exhausted;CM-MAC=xx:xx:xx:xx:xx:xx;CMTS-MAC=ff:ff:ff:ff:ff:ff:ff;CM-QOS=1.1;CM-VER=3.0;
Fri Jan 29 12:38:42 2010 Fri Jan 29 12:38:48 2010 Critical (3) No Ranging Response received - T3 time-out;CM-MAC=xx:xx:xx:xx:xx:xx;CMTS-MAC=ff:ff:ff:ff:ff:ff:ff;CM-QOS=1.1;CM-VER=3.0;
Fri Jan 29 12:38:49 2010 Fri Jan 29 12:38:49 2010 Warning (5) B-INIT-RNG Failure - Retries exceeded;CM-MAC=xx:xx:xx:xx:xx:xx;CMTS-MAC=ff:ff:ff:ff:ff:ff:ff;CM-QOS=1.1;CM-VER=3.0;
Fri Jan 29 12:38:57 2010 Fri Jan 29 12:38:57 2010 Critical (3) SYNC Timing Synchronization failure - Loss of Sync;CM-MAC=xx:xx:xx:xx:xx:xx;CMTS-MAC=ff:ff:ff:ff:ff:ff:ff;CM-QOS=1.1;CM-VER=3.0;
Fri Jan 29 12:39:22 2010 Fri Jan 29 12:39:22 2010 Critical (3) No Ranging Response received - T3 time-out;CM-MAC=xx:xx:xx:xx:xx:xx;CMTS-MAC=ff:ff:ff:ff:ff:ff:ff;CM-QOS=1.1;CM-VER=3.0;
Fri Jan 29 12:39:41 2010 Fri Jan 29 12:39:41 2010 Critical (3) SYNC Timing Synchronization failure - Loss of Sync;CM-MAC=xx:xx:xx:xx:xx:xx;CMTS-MAC=ff:ff:ff:ff:ff:ff:ff;CM-QOS=1.1;CM-VER=3.0;
Fri Jan 29 12:39:52 2010 Fri Jan 29 12:39:52 2010 Critical (3) Received Response to Broadcast Maintenance Request, But no Unicast Maintenance opportunities received - T4 time out;CM-MAC=xx:xx:xx:xx:xx:xx;CMTS-MAC=ff:ff:ff:ff:ff:ff:ff;CM-QOS=1.1;CM-VER=3.0;
Fri Jan 29 12:40:26 2010 Fri Jan 29 12:40:32 2010 Critical (3) No Ranging Response received - T3 time-out;CM-MAC=xx:xx:xx:xx:xx:xx;CMTS-MAC=ff:ff:ff:ff:ff:ff:ff;CM-QOS=1.1;CM-VER=3.0;
Fri Jan 29 12:40:33 2010 Fri Jan 29 12:40:33 2010 Warning (5) B-INIT-RNG Failure - Retries exceeded;CM-MAC=xx:xx:xx:xx:xx:xx;CMTS-MAC=ff:ff:ff:ff:ff:ff:ff;CM-QOS=1.1;CM-VER=3.0;
Fri Jan 29 12:40:45 2010 Fri Jan 29 12:42:41 2010 Critical (3) No Ranging Response received - T3 time-out;CM-MAC=xx:xx:xx:xx:xx:xx;CMTS-MAC=ff:ff:ff:ff:ff:ff:ff;CM-QOS=1.1;CM-VER=3.0;
Sat Jan 30 01:00:36 2010 Sat Jan 30 01:00:36 2010 Warning (5) TEK Invalid - Invalid Key Sequence Number;CM-MAC=xx:xx:xx:xx:xx:xx;CMTS-MAC=ff:ff:ff:ff:ff:ff:ff;CM-QOS=1.1;CM-VER=3.0;
Sat Jan 30 01:01:39 2010 Sat Jan 30 01:01:39 2010 Critical (3) No Ranging Response received - T3 time-out;CM-MAC=xx:xx:xx:xx:xx:xx;CMTS-MAC=ff:ff:ff:ff:ff:ff:ff;CM-QOS=1.1;CM-VER=3.0;
Sat Jan 30 01:02:25 2010 Sat Jan 30 01:02:25 2010 Warning (5) TEK Invalid - Invalid Key Sequence Number;CM-MAC=xx:xx:xx:xx:xx:xx;CMTS-MAC=ff:ff:ff:ff:ff:ff:ff;CM-QOS=1.1;CM-VER=3.0;
Sat Jan 30 01:04:47 2010 Sat Jan 30 01:04:52 2010 Critical (3) No Ranging Response received - T3 time-out;CM-MAC=xx:xx:xx:xx:xx:xx;CMTS-MAC=ff:ff:ff:ff:ff:ff:ff;CM-QOS=1.1;CM-VER=3.0;
Sat Jan 30 01:05:29 2010 Sat Jan 30 01:05:29 2010 Warning (5) TEK Invalid - Invalid Key Sequence Number;CM-MAC=xx:xx:xx:xx:xx:xx;CMTS-MAC=ff:ff:ff:ff:ff:ff:ff;CM-QOS=1.1;CM-VER=3.0;
Sat Jan 30 01:05:50 2010 Sat Jan 30 01:05:50 2010 Critical (3) No Ranging Response received - T3 time-out;CM-MAC=xx:xx:xx:xx:xx:xx;CMTS-MAC=ff:ff:ff:ff:ff:ff:ff;CM-QOS=1.1;CM-VER=3.0;
Sat Jan 30 01:07:04 2010 Sat Jan 30 01:08:17 2010 Warning (5) TEK Invalid - Invalid Key Sequence Number;CM-MAC=xx:xx:xx:xx:xx:xx;CMTS-MAC=ff:ff:ff:ff:ff:ff:ff;CM-QOS=1.1;CM-VER=3.0;
Sat Jan 30 20:20:50 2010 Sun Jan 31 21:27:43 2010 Critical (3) No Ranging Response received - T3 time-out;CM-MAC=xx:xx:xx:xx:xx:xx;CMTS-MAC=ff:ff:ff:ff:ff:ff:ff;CM-QOS=1.1;CM-VER=3.0;
Tue Feb 2 00:15:04 2010 Tue Feb 2 00:15:04 2010 Notice (6) DHCP Renew - lease parameters tftp file-Pcaa1a92007a50b13.cm modifie;CM-MAC=xx:xx:xx:xx:xx:xx;CMTS-MAC=ff:ff:ff:ff:ff:ff:ff;CM-QOS=1.1;CM-VER=3.0;
Tue Feb 2 18:18:24 2010 Tue Feb 2 18:18:24 2010 Critical (3) No Ranging Response received - T3 time-out;CM-MAC=xx:xx:xx:xx:xx:xx;CMTS-MAC=ff:ff:ff:ff:ff:ff:ff;CM-QOS=1.1;CM-VER=3.0;
Wed Feb 3 13:42:50 2010 Wed Feb 3 13:44:39 2010 Error (4) Map Request Retry Timeout;CM-MAC=xx:xx:xx:xx:xx:xx;CMTS-MAC=ff:ff:ff:ff:ff:ff:ff;CM-QOS=1.1;CM-VER=3.0;


Hopefully this will mean more to you than it does to me! :)

Thanks again.

Rich

[Sephiroth]

A primer (I hope).

It's all suitably complex. You have a two way circuit from your perspective.

Downstream power is needed to send data TO you from the server (CMTS). Upstream power is needed to send data to the cable modem FROM the CMTS.

......

Just a quick correction (and thanks to Broadbandings for his adjustments to my primer).

Upstream power is needed to send data to the CMTS from the cable modem.

---------- Post added at 09:22 ---------- Previous post was at 08:40 ----------

So the engineer came in the early afternoon on 03-Feb? And that's the current event log - nothing happened since in the log?

Upstream problems could have been explained against the T3 timeouts. Just why a downstream attenuator would correct that is beyond me (but my good friend BBings might have a suggestion based on his vastly greater depth of knowledge).

I noted also the downloaded configuration file on 02-Feb, which I take to be for 64QAM downstream modulation, but we can't see if you were 256QAM provisioned prior to that. It doesn't really speak to the upstream numbers but lurking there may be some significance. The 64QAM modulation allows greater downstream SNR tolerance (35 dB isn't great but is supposed to be more than OK for 64QAM).

What is significant to my reading is the number of codeword errors. You should look at your stats again, and if the numbers are rising, you have a problem that needs attention. At simplest, your modem could be faulty or there are loose/intermittemt connections somewhere, or noise ingress or something wrong in the cabinet.

To my simple mind, if your downstream is OK and your modem power/SNR are OK, then the codewords issue could be a combiner/splitter issue at the street cabinet. But I'm here, BBings is watching and the engineer needs to be there with some of these comments laid before him in advance.

HTH.

[Ignitionnet]

I noted also the downloaded configuration file on 02-Feb, which I take to be for 64QAM downstream modulation, but we can't see if you were 256QAM provisioned prior to that. It doesn't really speak to the upstream numbers but lurking there may be some significance. The 64QAM modulation allows greater downstream SNR tolerance (35 dB isn't great but is supposed to be more than OK for 64QAM).

The config file is nothing to do with downstream modulation.

[StumpyBloke]

I dont understand any of this stuff you guys are talking about :D and all I know is it used to work as expected upto a few weeks ago and now it doesnt, so I have made an official complaint to Virgin.

Thx for all the replies, much appreciated.

Cheers, Rich

[Ignitionnet]

I dont understand any of this stuff you guys are talking about :D and all I know is it used to work as expected upto a few weeks ago and now it doesnt, so I have made an official complaint to Virgin.

Thx for all the replies, much appreciated.

Cheers, Rich

Nah you don't need to understand or care, point is it's broken and there's nothing you can do about it so getting Virgin to sort it is the way to go :)

[StumpyBloke]

Yip lets hope they will! :)

Just noticed another thing which may or may not mean anything... whenever I run a speedtest from any site, during the upload part and at about 2/3rd of it the upload always drops sharply and instantly from about 800ish to 600ish.

Rich