50M : Packet loss, very slow speeds and pain

[GuestUK]

Hi all,

I'm getting a problem where the internet starts running very slow and then eventually drops all together. I'm trying to diagnose what's going wrong, but I'm at a bit of a loss. When it is working, I'm getting about 10% packet loss on a ping to google, in usual surfing, it's a painfully slow experience!

The Virgin Superhub is running in Modem Mode. Attempting to reach it at 192.168.100.1 99% of the time results in:

The server at 192.168.100.1 is taking too long to respond.

The other 1% of the time when I'm really lucky, after a long wait, I get a page load. I used these page loads to try to get to the log - which seemed to be suspiciously empty other than these items :

Network Log First Time Last Time Priority Error Number Description
20/11/2012 21:06:27 20/11/2012 21:06:27 Warning (5) 84020300 MDD message timeout;CM-MAC=;CMTS-MAC=00:30:b8:d7:9d:20;CM-QOS=1.1;CM-VER=3.0;
20/11/2012 21:07:18 20/11/2012 21:07:18 Critical (3) 82000500 Started Unicast Maintenance Ranging - No Response received - T3 time-out;CM-MAC=;CMTS-MAC=;CM-QOS=1.1;CM-VER=3.0;

Eventually, the internet comes back after a long wait, buy doesn't stick around for longr

My superhub information is showing:
Information Cable Modem EuroDOCSIS
Boot Code Version 2.3.0beta7
Software Version V2.37.01
Hardware Version 2.00
CA Key Installed

Other information and levels:

Downstream   	DS-1 	DS-2 	DS-3 	DS-4 	DS-5 	DS-6 	DS-7 	DS-8
Frequency (Hz) 	323000000 Hz 	267000000 Hz 	275000000 Hz 	283000000 Hz 	291000000 Hz 	299000000 Hz 	307000000 Hz 	315000000 Hz
Lock Status(QAM Lock/FEC Sync/MPEG Lock) 	Locked 	Locked 	Locked 	Locked 	Locked 	Locked 	Locked 	Locked
Channel ID 	56 	49 	50 	51 	52 	53 	54 	55
Modulation 	QAM256 	QAM256 	QAM256 	QAM256 	QAM256 	QAM256 	QAM256 	QAM256
Symbol Rate (Msym/sec) 	6.952000 	6.952000 	6.952000 	6.952000 	6.952000 	6.952000 	6.952000 	6.952000
Interleave Depth 	I=12
J=17 	I=12
J=17 	I=12
J=17 	I=12
J=17 	I=12
J=17 	I=12
J=17 	I=12
J=17 	I=12
J=17
Power Level (dBmV) 	-0.5 dBmV 	1.8 dBmV 	1.7 dBmV 	1.0 dBmV 	0.5 dBmV 	1.1 dBmV 	0.6 dBmV 	0.0 dBmV
RxMER (dB) 	37.1 dB 	34.4 dB 	37.8 dB 	36.3 dB 	37.8 dB 	36.7 dB 	38.2 dB 	38.1 dB

Upstream   	US-1 	US-2 	US-3 	US-4
Channel Type 	2.0 	2.0 	N/A 	N/A
Channel ID 	3 	1 	N/A 	N/A
Frequency (Hz) 	27400000 Hz 	45800000 Hz 	N/A 	N/A
Ranging Status 	Success 	Success 	N/A 	N/A
Modulation 	QAM16 	QAM16 	N/A 	N/A
Symbol Rate (Sym/sec) 	5120000 	5120000 	N/A 	N/A
Mini-Slot Size 	128 	128 	N/A 	N/A
Power Level (dBmV) 	49.3 dBmV 	47.0 dBmV 	N/A 	N/A
T1 Timeouts 	0 	0 	N/A 	N/A
T2 Timeouts 	0 	0 	N/A 	N/A
T3 Timeouts 	49 	49 	N/A 	N/A
T4 Timeouts 	4 	4 	N/A 	N/A

 General Configuration Network Access 	Allowed
Maximum Number of CPEs 	1
Baseline Privacy 	Enabled
DOCSIS Mode 	EU DOCSIS 3.0
Config File 	
Primary Downstream Service Flow SFID 	25002
Max Traffic Rate 	133000000 bps
Max Traffic Burst 	10000 bytes
Min Traffic Rate 	0 bps
Primary Upstream Service Flow SFID 	25001
Max Traffic Rate 	12000000 bps
Max Traffic Burst 	16320 bytes
Min Traffic Rate 	0 bps
Max Concatenated Burst 	16320 bps
Scheduling Type 	BestEffort

At the moment on doing a speed test, I'm getting

Ping: 10ms
Download Speed: 23mbps
Upload Speed: 10.82mbps

But when it starts getting bad, I can't even get the speed test past the ping!

This should be on the 50mbps plan I believe

Any ideas? I'd really appreciate any thoughts or suggestions :-)

Thanks!

[thenry]

your config states your on 120meg down and 12meg up. connection levels look good. T3, T4s.. have you called in and asked an agent to check the network? some offshore agents know how to check but most seem to be obsessed with turning the SH firewall off even in modem mode

get a ping monitor going on thinkbroadband.

[ferretuk]

Originally Posted by GuestUK

Hi all,

I'm getting a problem where the internet starts running very slow and then eventually drops all together. I'm trying to diagnose what's going wrong, but I'm at a bit of a loss. When it is working, I'm getting about 10% packet loss on a ping to google, in usual surfing, it's a painfully slow experience!

The Virgin Superhub is running in Modem Mode. Attempting to reach it at 192.168.100.1 99% of the time results in:

The server at 192.168.100.1 is taking too long to respond.

A few thoughts:

Have you turned the SH off and on again? Does the ping to the SH improve if you do?
Have you turned your router off and on again?
Are you connected wirelessly to your router? Test via an Ethernet cable if you are.
Do you have any devices on your LAN that you can ping at the same time as pinging the SH?
Try plugging your PC directly to the SH

I suggest that getting to the bottom of the apparently unreliable connection to the SH ought to be your first move...

[qasdfdsaq]

Yeah, if you have trouble accessing the Superhub then ping the Superhub. The problem may be local.

[GuestUK]

Thanks very much for the replies!

Restarting the SH seems to solve the problem for a while, but then it comes back. After restarting, connection to the SH returns to normal - accessing the admin pages becomes instant, internet works well again etc.

I've been using the same setup for years without a problem, but I'm connected via Ethernet to a Billion router which is connected to the SH in modem mode. Rebooting the router doesn't fix the problem, only rebooting the SH. No problems reaching any other network devices when the problem occurs.

It almost seems that when the connection goes unstable, the SH becomes so busy trying to work with the connection that it doesn't have time to respond to the admin interface.

It generally seems to happen at busy times of day (e.g. the evenings) - the connection speed starts to get lower and lower (from say 78mbps normally to about 7mbps), then eventually dies altogether. Even restarting the SH brings the connection back up but still at a slower speed and still unstable. It only tends to become more stable into the early hours of the morning or less busy times of day.

Is it perhaps just normal that the VM network just gets busy, and when it does, you lose most/all of your internet and the SH isn't great at coping?

[ferretuk]

Originally Posted by GuestUK

It almost seems that when the connection goes unstable, the SH becomes so busy trying to work with the connection that it doesn't have time to respond to the admin interface.

Probably still worth bypassing your router and plugging a PC directly into the SH (still in modem mode) to prove where the fault lies.

Then it's a phone call to VM armed with the facts...

[Sephiroth]

I can see what's wrong. The 2nd downstream channel has poor SNR (not out of theoretical range for 256QAM but at 120 meg it's poor). This means that your SH cant properly assemble packets if the interleaved data it receives is corrupted (post-RS errors).

You can check this for yourself in modem mode (I think that's your mode). You log into the admin page of the SH. You invoke a new browser tab and put this into the URL line:

http://192.168.100.1/advanced_list.asp

You will see the full advanced manu. Get to the stats and you'll see the Pre-RS and Post-RS errors. I bet that DS channel 2 looks tasty.

The T3 errors occur if the modem can't properly read the keep-alives and so can't respond; the T4 event occurs when this happens on 16 consecutive retries and so reboots.

If a single channel is misbehaving then it's either the SH (unlikely) or something in the optical node which a visiting engineer can't fix. A reboot (or better still leaving the SH off overnight) might give you different downstream channels and that could cure the condition.

Hope that helps.

[qasdfdsaq]

That shouldn't be giving him trouble accessing the Superhub locally though.

[Sephiroth]

Originally Posted by qasdfdsaq

That shouldn't be giving him trouble accessing the Superhub locally though.

Originally Posted by GuestUK

Hi all,

I'm getting a problem where the internet starts running very slow and then eventually drops all together. I'm trying to diagnose what's going wrong, but I'm at a bit of a loss. When it is working, I'm getting about 10% packet loss on a ping to google, in usual surfing, it's a painfully slow experience!
The Virgin Superhub is running in Modem Mode.

Any ideas? I'd really appreciate any thoughts or suggestions :-)

Thanks!

I hope you don't mind that I have tried to answer the substantive part of the question, Qasi.

[qasdfdsaq]

Yes, but as he's seeing the same symptoms accessing any web page, including the Superhub's own internal page, you've got to consider the possibility of a common cause.

[Sephiroth]

Such a common cause would point to the SH.