Superhub : My Network

[TROTER]

Thought I would share a diagram of my network. As many of us have a growing number of devices within our homes I often wonder how our house would cope with just the standard virgin equipment.

This network copes with all that is thrown at it, 2 TVs streaming, Xbox gaming phones and tablets all at the same time. No buffering dropouts or resetting equipment, rock solid.

Although my Linksys is now a few years old now which does the brunt of the work within my network I wander if upgrading to a newer router with a more powerful CPU and memory would make a difference? Would the gigabit LAN perform any better on a newer model?

The only worry I have is the ever degrading noise within the virgin network as shown by my superHub 31dB down stream which I am told is within spec. This used to be 39dB a few years ago.

Is the large number of Pre RS errors anything to be concerned about?

[qasdfdsaq]

A new router would not make any difference unless you're planning on moving to the 300Mbps+ packages in the future.

There's no such thing as gigabyte LAN. All your devices are already gigabit LAN. Since all gigabit devices operate at... a gigabit, a new gigabit router won't make any difference.

Your SuperHub (no not Supper hub, I would not ever have a router for supper) does not show downstream noise. Your SNR (if that's what you're talking about) of 31dB is not within spec.

[TROTER]

Originally Posted by qasdfdsaq

A new router would not make any difference unless you're planning on moving to the 300Mbps+ packages in the future.

There's no such thing as gigabyte LAN. All your devices are already gigabit LAN. Since all gigabit devices operate at... a gigabit, a new gigabit router won't make any difference.

Your SuperHub (no not Supper hub, I would not ever have a router for supper) does not show downstream noise. Your SNR (if that's what you're talking about) of 31dB is not within spec.

Thanks for pointing out my mistakes, Why is it that when I have reported the SNR in the past I have been told its within spec contradictory to what you guys report within this forum? ( SNR no lower than 34 dB)

[qasdfdsaq]

I don't know. VM support are well known for telling you fibs to get you off the phone.

[TROTER]

I did have a tech out last year he changed the superHub and said all is fine with SNR. Problem could be with out door splitter, cable or further up line to cabinet? Any advice to how I can get this rectified?

[pip08456]

Get another tech out.

[General Maximus]

I am just so glad that you have got a super spiffing network with a Linksys router. I am amazed Qas resisted the temptation for one of his witty comments. The EA4500 is famous for being a top notch router dude so all I am going to say is if ain't broken don't fox it.

[TROTER]

Can not get a visit from a tech until SNR is 30dB, I was told to monitor the level and give them a ring back when levels drop.
They have shown this low before in the past, what a palaver!

---------- Post added at 18:30 ---------- Previous post was at 18:27 ----------

Originally Posted by General Maximus

I am just so glad that you have got a super spiffing network with a Linksys router. I am amazed Qas resisted the temptation for one of his witty comments. The EA4500 is famous for being a top notch router dude so all I am going to say is if ain't broken don't fox it.

Well I was going to have my router for supper!

[MUD_Wizard]

Originally Posted by TROTER

Can not get a visit from a tech until SNR is 30dB, I was told to monitor the level and give them a ring back when levels drop.
They have shown this low before in the past, what a palaver![COLOR="Silver"]

You shouldn't accept RxMER less than 34.5 dB.

VM's RxMER threshold is around 30 dB as you say, though they have been known to raise network faults around the 32-33 dB mark, at least via the forum anyway.

I'd advise you to create a thread on community.virginmedia.com and post a Thinkbroadband BQM graph, which should show lots of red packet loss due to noise, along with your modem stats.

Btw, unless things have changed recently, general tech's have no equipment to test/fix/faultfind SNR levels.

A network engineer would need to be called out, to trace where the problem is in the network (noisy modems somewhere, cabinet amplifier dying, machinery interference etc), and that won't happen until the fault is raised to networks with a fault reference number.


---------- Post added at 20:28 ---------- Previous post was at 20:16 ----------

Originally Posted by qasdfdsaq

Your SuperHub (no not Supper hub, I would not ever have a router for supper) does not show downstream noise.

?

[vm_tech]

Although the downstream SNR is on the low side, is it causing any problems? Because you don't seem to be reporting any actual issues. Worry about it when a problem arises. As that's the downstream levels, it won't show up as a noise fault. I've never come across noise on the forward spectrum, although I'm told it is possible, mainly on analogue.

[qasdfdsaq]

Originally Posted by MUD_Wizard

?

It displays received signal power and SNR. It doesn't display a figure for noise.

[TROTER]

Thanks to all for your information.

[MUD_Wizard]

Originally Posted by vm_tech

Although the downstream SNR is on the low side, is it causing any problems?

While it's always a good idea to ask this question, if someone's RxMER is around 31 dB they'll be prone to several orders of magnitude more pre-rs errors and a much higher likelihood of post-rs errors, than someone at 35 dB.

If it's not causing problems it would be a miracle.

Originally Posted by vm_tech

I've never come across noise on the forward spectrum, although I'm told it is possible, mainly on analogue.

Really? Happens on-and-off for a few months of every year to most cable users, and that's at the fault level. Maybe you don't notice. If I wanted to be pedantic I could say there's always noise on the forward spectrum, that's what is described by the noise floor level.


---------- Post added at 01:36 ---------- Previous post was at 01:22 ----------

Originally Posted by qasdfdsaq

It displays received signal power and SNR. It doesn't display a figure for noise.

RxMER is the ratio of average signal constellation power to average constellation error power, in the receiver after demodulation. Not quite the same thing. An approximation of SNR yes, but RxMER does factor in impairments due to noise above the noise floor.


---------- Post added at 01:43 ---------- Previous post was at 01:36 ----------

Originally Posted by TROTER

Thanks to all for your information.

Unless you suspect the coax cabling in your home has been nobbled then I wouldn't stress about it (as annoying as these intermittent faults are). There's little you can do, apart from post a thread on the community forum or notify them by phone (as you have done). VM wait until enough customers complain before doing something and you calling up every day won't change that.

I generally post a thread, sit back and keep an eye on my Thinkbroadband graph, then switch to 3G phone whenever it drops out.

These things usually get resolved without further intervention in a few days to a couple of weeks.

[Kushan]

Originally Posted by TROTER

Thanks for pointing out my mistakes, Why is it that when I have reported the SNR in the past I have been told its within spec contradictory to what you guys report within this forum? ( SNR no lower than 34 dB)

Possibly because the SNR targets have shifted over the years as the network has migrated from DOCSIS1 to DOCSIS2 to DOCSIS3. I know when I was there, there was still a distinction between ex-NTL and ex-TW areas in terms of acceptable power levels and SNR (Likely to do with the CMTS/UBR systems used by each franchise). Not all of the agents paid particular attention to the distinctions, though.

[MUD_Wizard]

Originally Posted by Kushan

Possibly because the SNR targets have shifted over the years as the network has migrated from DOCSIS1 to DOCSIS2 to DOCSIS3.

That's not it at all. The SNR targets/thresholds haven't shifted for 256 QAM over the years and 256 QAM has been used for a long time.

SNR thresholds are based on modulation, not whether it's Docsis 1/2/3 as such. Docsis 1 did introduce support for QPSK and 16 QAM modulations and Docsis 2 added 8-QAM, 32-QAM and 64-QAM.

256 QAM lower threshold ranges from 28 to 30 dB.
Add 3 dB headroom for local conditions and you get 33 dB.
VM will often quote one or the other of those figures, but they haven't moved.

Data corruption, visible in the form of post-rs errors, usually starts around 34 dB, but the noise errors need to come in clumps in order to trigger post-rs errors. If they're spread out enough then you'll just get lots of pre-rs errors and no or few post-rs errors.

However, to make things more complex different Superhubs display slightly different RxMER figures on the same circuit, which you have to take into account when giving advice.


Btw, the next modulation down is 64 QAM, the lower threshold for which is 22 to 24 dB. So they won't be quoting that.

Originally Posted by Kushan

I know when I was there, there was still a distinction between ex-NTL and ex-TW areas in terms of acceptable power levels and SNR (Likely to do with the CMTS/UBR systems used by each franchise). Not all of the agents paid particular attention to the distinctions, though.

There are slight differences in power level ranges due to area, but the current range of -6 to +10 dBmV (downstream) generally holds, with some fine tuning by area. RxMER / SNR has an impact on how far outside that range you can go before experiencing problems.

CMTS manufacturers is a whole other conversation.