My Network
 

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?

Re: My Network
 

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.

Re: My Network
 

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)

Re: My Network
 

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

Re: My Network
 

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?

Re: My Network
 

Get another tech out.

Re: My Network
 

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.

Re: My Network
 

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 ----------

Well I was going to have my router for supper!

Re: My Network
 

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 ----------

?

Re: My Network
 

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.

Re: My Network
 

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

Re: My Network
 

Thanks to all for your information.:)

Re: My Network
 

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.

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 ----------

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 ----------

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.

Re: My Network
 

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.

Re: My Network
 

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.

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.

Re: My Network
 

You need to define "A long time". I'm talking about ~5 years ago now and I don't know what the OP's timeframe is, nor if there are agents that still use the "old" guidelines (Wouldn't surprise me).

I'm not disagreeing with anything you're saying, however all I can tell you is what VM staff were actually trained to look at. I'm not saying it's correct, just that's what the training told agents to look for. Modulation never came into it (it was very briefly glossed over).

Again, agents were taught to look at it slightly differently. They largely ignored post-rs errors for individual customers and instead only looked at the errors on a specific line/cable. They have (or had) a tool that gave a lovely colourful view on the errors in that area and a lovely arbitrary %. If the % was above a certain number, it was raised as an outage. If not, it was left to it (Ironically, the threshold was something like 30% but when a line was completely down, the tool only ever reported a static 25% - NFF!). For individual customers, it was T3 and T4 timeouts that mattered in this case (As well as power/SNR).

No indeed, they quoted 20dB in some areas as being acceptable (ex-NTL if I recall).



The power levels these days are definitely more consistent and it was aligned internally with the Docsis 3 rollout, however prior to that the range was much larger (I want to say -10 to +12 but I'm not 100%) and again, did differ by area on occasion.

If I had to guess, the guidelines being different for ex-TW and ex-NTL possibly stem from the merging of the two. I would not be surprised if both companies simply had different guidelines for their agents and Virgin simply decided to keep treating them separately until they got their ducks in a row.

Re: My Network
 

Virgin introduced Docsis 3 in 2009, with multiple bonded 256 QAM downstreams channels for 50Mb, however 256 QAM would have been available on Docsis 2 before that (but not at launch of Docsis 2).

http://about.virginmedia.com/press-r...test-broadband
http://forums.thinkbroadband.com/vir...fpart=all&vc=1

The number of channels bonded doesn't change the SNR thresholds set by the Docsis specifications. So, sometime after 2003 and well before 2009. Unless VM skipped Docsis 2 for some areas..

Of course most people will have been on Docsis 1 and gradually been moved over to Docsis 3.



The flap list etc for area outages.

T3 and T4 timeouts are upstream. It's SYNC errors and MDD's for downstream.

As I said, it's related to modulation. For more info see: http://community.virginmedia.com/t5/...4/td-p/2271297


Power level ranges changed over the years due to aggregate/bonded downstream power and the number of bonded channels changing. See the primer linked above, it has a section devoted to it.

Sure there were differences as far as I understand it. Though not on the basics.

Re: My Network
 

Again, you're not really listening to what I'm saying. Internally at Virgin, they have shifted the SNR and power level targets over the years. Again, it seems TW and NTL had different targets as well for whatever reason (Either different equipment in use, different standards, or whatever). The guidelines used to be a lot looser than they are now, so it may well have even been a cost-cutting measure, who knows.

Also, when Virgin first released 50Mbit, not all agents were trained to deal with it. There was a special "50Meg" team of agents and only those agents would handle 50meg calls (as a customer you had a special number, or if you phoned through to regular BB support, you'd get transferred into the "50meg queue"). Part of this training involved understanding different power levels and SNR targets (As well as the channel bonding). If the only difference was that channels were bonded, then the "training" wouldn't have taken a week and been done by all agents.

And it doesn't matter. From the agent's perspective, they don't care if it's upstream or downstream, just that they're either going to send a tech to the customer or raise an outage for the area - so that's how faults are diagnosed, either it affects the customer or it affects the area. Beyond that, the responsibility ends for the agent so they were never trained to understand what was really going on or what those errors truly meant. That was the job of either the fault tech or the outage teams to determine.


Once more, and I really must stress this, that's not how the agents were trained. The agents were not trained to check modulation and then assess power levels, they were simply told "If this customer is ex-TW, the levels are x and if they are ex-NTL, the levels are y". Again, I'm not saying this was correct (In fact I know later this was very very wrong as new equipment was installed in both areas) and I'm not disagreeing with your statements, I'm simply telling you that this is how the agents were trained to identify the "correct" power levels. There were 3 sets - TW, NTL and DOCSIS3. Also, not all agents were remotely kept up to date with this either, not all of them got retraining as the targets were adjusted.

Once more, I'm telling you how agents were trained to identify it, not what the actual reasoning is. And this is probably why different agents gave out different information over the years.


I was not present pre-merge so I cannot comment.