Re: Why I regret joining virgin media
 

There's some downstream RF issues that don't show up on the SNR reported by the modem, same goes for upstream in the other direction too.

Challenge is to find someone at VM who'll actually persue the matter for you.

Re: Why I regret joining virgin media
 

Igni got in before me!

The Motorola BSR problem that's gathered under that single ticket is characterised by TEK and T3 errors in the event log (and codeword errors in the stats). You don't have the TEK error and so it's prolly a leap to align your problem with the Motorola BSR fault or whatever it is.

Of course I'm just being logical based on the tiny evidence we see. Either VM are massively incompetent technically or the so-called BSR problem is massively complex, but people with the right equipment seem not to have discovered the cause of the Motorola problem.

Re: Why I regret joining virgin media
 

Codeword errors are not related to TEK / T3 beyond that downstream errors may cause TEK / T3s due to BPI+ / RNG-RSP messages being lost due to the codeword carrying them erroring.

Segmentation of downstream traffic into codewords is done by different bits of hardware and software within the line cards from those governing control messages.

Of note also is that only a limited subset of modems were experiencing instability, errored codewords would affect every modem on the line card.

Re: Why I regret joining virgin media
 

Yes - The associations I mentioned are anecdotal, albeit fairly consistentl. I posted this in the other place:

All cable traffic related to an authorised CM is encrypted with a Primary Security Association ID. The key for this encryption is the TEK (and is derived from the CMTS allocated Authorisation Key).

The TEK has a finite lifetime (as does the Authorisation Key), and periodically this has to be refreshed as part of the authorisation maintenance process. The TEK packet header holds the TEK sequence number. The CM requests a new TEK from the CMTS. The response includes the new TEK and the lifetime remaining in the current TEK.

Now, here's what I think might happen. If there is an upstream problem, the next (delayed) packet sent upstream could contain the TEK sequence number of an expired TEK. hence the message: TEK Invalid - Invalid Key Sequence Number

In this case, there is a disconnexion of your session because you are non longer obeying the Security Association protocol.

There could be other causes of the Invalid Key Sequence Number. It could simply get corrupted on the way up or become corrupted at the CMTS.

The T3s are not yet a disconnect, but could be a symptom of the TEK errors.

Note that this response, which is more or less accurate, casts little/no light on what could be the cause of the BSR issues.

Re: Why I regret joining virgin media
 

The issue is actually with a broken BPI+ implementation on the CMTS side causing the modem and the CMTS respective BPI+ state machines to go out of sync. The KSN only goes across the wire during BPI+ TEK state machine updates. A modem would have to send multiple TEK refresh requests within a very short period, milliseconds, for this to be due to upstream impediments.

Modems aren't disconnected via T3s / T4s, if they aren't properly authenticated and authorised their primary service flow would be de-authorised, reflected in the modem by a BPI+ state of 'denied'.

There is a grace period, default an hour, to mitigate modems being disconnected due to their BPI+ state machine falling out of sync with the CMTS.

Control messages, ranging requests, etc, are not encrypted by BPI+.

Re: Why I regret joining virgin media
 

I,m not claiming to understand what your saying here Igni/seph, but what happens if the modem doesn't know what time it is.

A lot of problematic modems are showing "time not established" errors, despite numerous attempts to re-establish it.

So what I,m curious about, can the T3 actually cause an outage/loss of service if the modem doesn't know what time it is, going off what's written above in bold

Apologies if this is a dumb question

Re: Why I regret joining virgin media
 

Look at all that info we have gleaned from him Seph :D

Thanks guys, they are sending me a different modem to try out on the DOCSIS 1 or 2 so I'll update when Ive tried that, going to be 3-5 days. In the meantime he has promised to chase up the codeword issue though he was in the past told by networks that they wont cause any issues

Re: Why I regret joining virgin media
 

Spot on! Gotta get that book.

---------- Post added at 16:18 ---------- Previous post was at 16:12 ----------

Igni doesn't think I know what I'm saying! :LOL: He's good, eh?

ToD synchronisation isn't a show stopper AFAIK. The modem substitutes a default time (and its clock ticks are then good). Every 5 minutes it tries again to synchronise time, and so on. All other functions perform, including the 30 second ranging request.

Without inside knowledge, I can't say why the ToD errors occur - but it is a discardable request from the CM and it is possibly due to a large number of CMs simultaneously trying to get ToD after restart or some other event.

Re: Why I regret joining virgin media
 

Damnit :D

---------- Post added at 16:31 ---------- Previous post was at 16:26 ----------

It's optional for D1/1.1/2.0 and some CMTS don't have one configured. As you say modems don't really need the time to function they just need to stay in sync with the CMTS, same as a clock that hasn't been set still knows how long a second is a modem that hasn't been 'set' by ToD still knows what a 6.25us tick is.

---------- Post added at 16:33 ---------- Previous post was at 16:31 ----------

You have never worked with cable practically, you're reciting what Brady Volpe and others say which doesn't necessarily mean you totally understand it, and of course regarding specifics, optional and non-standard configs Virgin's mileage may and does vary, as has caught me out a few times since I left too :)

Re: Why I regret joining virgin media
 

Seph has been right all along about my issues even when 2nd line weren't acknowledging any issues so good on Brady I say :D :p: Infact he near enough diagnosed my first fault that was found around 7 weeks before it was found by VM! which was noise on the line. Im going to have to have a google of this Volpe, Im quite enjoying learning the ins and outs of cable :)

My cisco modem has arrived but I wont be trying 10Mb until monday, just posting this graph so I have something to refer back to and compare with the new modem, the red bars are packet loss (also posting it in the hope the CEO guy will see it :D ) actually scrap that, Ive just emailed him the graph, he must hate me :)

Look at that pabs and I still managed to kick ass on BFBC2 :angel: :p: It always seems to be the osr hop that things start bad

Re: Why I regret joining virgin media
 

Well if you want to get into a peeing contest have a laugh at this :shocked: :D

Re: Why I regret joining virgin media
 

Bloody show off :D

Quite odd that Im looking forward to 10Mb!

Re: Why I regret joining virgin media
 

You started it :D

In a way so am I, as long as it works that is, I rang Mr CEO up today just to report the upload light flashing continuously last night (no internet), he said something about that might indicate a specific fault (or at least it did on the old modems), he wasnt sure what, but said he would look into it.

Either way roll on next week, keep your fingers and toes crossed that I will be back to kickin yo ass asap. :D

Re: Why I regret joining virgin media
 

Seph is great for putting things into focus and pointing out when things aren't as they should be though in your case not diagnosis, he pointed out the fault rather than its' cause, which is of course very difficult to narrow down without access to the network. Big numbers on modem stats in the 100s of millions without Hz next to them are usually a giveaway :)

Regrettably your case goes to show how incompetent VM can be. Google would tell you the answer in a few minutes as those 9 digit numbers do stick out a touch in the modem stats.

A quick Google for "Correctable Codewords" brought up http://www.dslreports.com/forum/r237...internet-speed amongst other matches.

http://www.dslreports.com/ is a great site for wanting to know more about cable. No offence intended to this site's readership but the level of knowledge there tends to be considerably higher due to how much bigger cable is in the States. I tend to troll there more than here for technical related stuff.

I tend to leave you in Seph's capable hands to look after you as only he can :)

Re: Why I regret joining virgin media
 

Hey dont be like that I value your input!!! :D Thanks for the links :)


Right I went on to DOCSIS1 10Mb and it did seem slightly better gaming wise, speeds are consistent, normally around 11/12 down. The part of the network Im now on only hits 30% utilisation max. VM said Ive had 15000 correctables in 24 hours which they said is nothing to worry about. I did experience some bad lag whilst gaming, I ran ping plotter and some parts of the graph dont look that good. Im now trying out the 20Mb service but its looking like Im going to have to stay on that until the 50Mb service problems are resolved, god damn motorola!

Ive attached some ping plots but Ive been told they cant guarantee pings and packet loss so maybe this is as good as it gets. I did have some graphs showing pings over 1000ms but I forgot to save them. At least my speeds are now stable


https://www.cableforum.co.uk/images/...2010/04/21.png

Downstream Status

Operational
Channel ID

3
Downstream Frequency

331000000 Hz
Modulation

256QAM
Bit Rate

20480000 bits/sec
Power Level

0.7 dBmV
Signal to Noise Ratio

39.0 dB
Upstream Channel
.

Upstream Status

Operational
Channel ID

3
Upstream Frequency

29200000 Hz
Modulation

16QAM
Symbol Rate

768000 bits/sec
Power Level

41.0 dBmV