Appalling unreliability

This Sunday 1st December, my pppd service on Linux has logged that the VDSL modem was disconnected and had to reconnect 19 times. This unreliability I've been having is therefore, unfortunately, getting worse. I will be contacting Zen tech support when they open on Monday but I just thought this fact should be noted. At one point, the modem was disconnecting so often I basically lost the internet connection for 10 minutes and had to forfeit a chess game I was playing. I know I'm not paying for a guaranteed 100% uptime leased line or something, but surely there is SOME implied level of service quality for a broadband service? This is totally unacceptable. Yet I can't seem to find anything on Zen's website about any service guaranteed for their fibre broadband. For an ISP that touts how great its network is, this is pretty surprising.

If this continues and cannot be resolved, I may have to go back to ADSL2+. FTTC is not worth it if it means you can't rely on your connection not to drop out all the time.

Edited by jez9999 (Mon 02-Dec-13 01:20:48)

What speeds is the line running at? Also its Christmas light season, so if someone nearby has just lit the street up, then it may be they are the issue.

The speed and latency are fine, staying around the level in the speed test linked in my sig; 75/15. It's the fact that it keeps disconnecting that's the problem.

Why would Christmas lights cause this?

I now have no broadband service whatsoever and am connecting to the net using my mobile's broadband tethering.

It looks lile my local cabinet is screwed as BT has a fault reference indicating "A Network Element Down is the root cause". This is the second time I've had my connection cut off because of such an error. Seems like 21CN is falling apart at the seams.

21CN is the BT Wholesale network. What you're talking about here is Openreach's GEA-FTTC.


Frustrating as it is, the total failure of your line may well have done you a favour. It seems odd that a line that synchronises at a fairly high speed and does not seem to have been subjected to speed drops by DLM is so flaky, but, as MrSaffron has said, flashing Christmas lights or a similar source of REIN might be the root cause.

I hope that the root cause is something more immediately terminal and straightforward to fix than REIN, such as a dodgy line card port in the DSLAM. Finding permanent faults is often easier than intermittent faults.


What are Zen proposing to do now?

In reply to a post by jez9999:

Why would Christmas lights cause this?

interference in the relevant signal bands.

Does your VDSL connection to the router stay up (I guess you have to rely on the lights to tell you) but the PPP session drop ? What timeout settings do you have on PPP.

Nothing, basically. BT have "cleared" the fault, and for now, the connection is back up. I wouldn't be surprised if I continue to see what I've been seeing for the past few weeks, which is more intermittent PPP disconnections. "Dodgy line card port" is sounding about right given the symptoms.

Do you mean the VDSL connection to the modem? It appears to stay up as the DSL light stays on. The PPP settings are that it tries a reconnection after 4 failed LCP echos, and the timeout for each echo is 5 seconds.

A bit left field here, but it might be worth trying a different network interface in your Linux box or temporarily using the Zen supplied router instead to see if that makes a difference to your PPP layer stability.

One of three threads abut this the OP has started today, with two previous.

Considered a longer timeout for the echo timeout?

if the VDSL is staying up, then suggests not an interference issue, but differences in how FTTC handles things and getting your Linux box to play nicely.

The joy of using one of the non-standard routers is getting it configured just right.

If this was me I'd be ditching the Linux box for a few days to try another router and see if things are stable, before pestering ISP. www.sinet.bt.com may detail the spec for LCP timeout

In particular SIN 498 is a likely candidate for FTTC.

+1 for ditching the linux box for a while. I've had a fair amount of issues with this kind of setup in the past. Use the ISP supplied router for a week and see how that goes.

As for xmas lights - essentially they generate interference in the same band as the broadband so they can cause interference down the broadband line which causes dropouts etc.