PPP disconnection when line sync still up. Why?

Hi,
I've recently started to have issues with my ADSL PPP connection dropping out even though the line remains synchronised. Yesterday and today this happened at the exact same time, to the minute (08:41am BST) and I know it has happened at very close to that same time at least one more time recently. My line has been pretty good for a long time so I don't know why I'm suddenly seeing issues.

Some facts: 21CN connection of about 4km length. Typical sync speeds from 3 to 4.5Mbps. Speedtouch ST516v6 router mounted next to master socket with short cable between. ADSL Nation faceplate filter with cordless phone base station connected and until yesterday Sky HD+ box. Also got an alarm dialler connected to the filtered connections on the back of the faceplate. Speedtouch was bought in Feb 2011 to replace one of the same type which had been running for about 4 years. Faceplate filter is probably 4 or 5 years old now.

I spoke to Zen TS and didn't really get anywhere other than a description of the fault finding process which I am working through just now. So far I have removed the Sky HD telephone connection and this has not cured the issue. I also removed my cordless base station tonight when another dropout occurred and the connection was very slow to reconnect which leads me to believe it's not the phone either.

I was so sure that the regularity of the fault pointed to some sort of issue at Zen's end but maybe my faceplate filter is reaching the end of useful life. The odd thing is that on both occasions, I've had the dropout when I've been alone in the house with nobody using any electrical or electronic equipment or phones etc. The central heating has been off (no spark interference) and I was just reading the morning news on my iPhone via WiFi when it went off. Both times at exactly 08:41am.

I've pulled the log files from my router and it shows more disconnections than just the ones I've noticed. Some of these have happened when nobody else was in the house. Note that through all of these PPP dropouts, my line sync has remained good at 4.5Mbps or thereabouts. (Note times are in GMT so add 1 hour for BST)


<132> SysUpTime: 00:00:55 PPP link up (Internet) []
<132> Sep 5 18:34:25 PPP link down (Internet) []
<132> Sep 5 18:43:34 PPP link up (Internet) []
<132> Sep 5 21:38:31 PPP link down (Internet) []
<132> Sep 5 21:38:49 PPP link up (Internet) []
<132> Sep 6 07:41:55 PPP link down (Internet) []
<132> Sep 6 07:42:42 PPP link up (Internet) []
<132> Sep 6 20:54:55 PPP link down (Internet) []
<132> Sep 6 21:00:07 PPP link up (Internet) []
<132> Sep 7 07:41:02 PPP link down (Internet) []
<132> Sep 7 07:52:03 PPP link up (Internet) []
<132> Sep 7 15:00:38 PPP link down (Internet) []
<132> Sep 7 15:03:32 PPP link up (Internet) []
<132> Sep 7 15:03:35 PPP link down (Internet) []
<132> Sep 7 15:03:36 PPP link up (Internet) []
<132> Sep 7 15:03:58 PPP link down (Internet) []
<132> Sep 7 15:06:56 PPP link up (Internet) []
<132> Sep 7 15:20:53 PPP link down (Internet) []
<132> Sep 7 15:24:26 PPP link up (Internet) []
<132> Sep 7 15:26:39 PPP link down (Internet) []
<132> Sep 7 15:30:14 PPP link up (Internet) []
<132> Sep 7 15:31:10 PPP link down (Internet) []
<132> Sep 7 15:32:16 PPP link up (Internet) []
<132> Sep 7 15:33:14 PPP link down (Internet) []
<132> Sep 7 15:34:36 PPP link up (Internet) []
<132> Sep 7 18:36:27 PPP link down (Internet) []
<132> Sep 7 18:37:23 PPP link up (Internet) []
<132> Sep 7 18:41:04 PPP link down (Internet) []
<132> Sep 7 18:42:17 PPP link up (Internet) []
<132> Sep 7 18:43:34 PPP link down (Internet) []
<132> Sep 7 18:44:13 PPP link up (Internet) []

Anyone seen anything like this before? My next move is to remove the faceplate filter and connect a brand new (bought with the Speedtouch in Feb and unused) ADSL filter and see how I get on over the next 24 hours.

Really annoying so if anyone has any ideas please let me know.
Thanks,
Craig.

Have Zen said anything about the possibility of an exchange issue i.e. its connection to the rest of the BT network.

They do have to do the bog standard diagnostics though.

Strangely enough, this just happened to me this evening (though I'm not with Zen). From 8.00pm onwards, I started to get packet loss until the loss is so great, the PPP drops, and reconnects. It does this 2-3 times over a half hour (error) period, until about 9.15pm, all is good again. This has not happened before for the entire history of my line, so I find it a bit mysterious.

I put it down to some obscure line interference, but having said that, no actual re-sync has occurred on the line. It's almost as if because I'm running interleave mode, the ADSL modem has just refused to re-sync, and just held strong and solid, even though it may have been experiencing corrupted frames causing the PPP link to disconnect. I don't really understand why, if it's that bad, it wouldn't re-sync, but according to my modem logs, it definitely hasn't.

Although it may not have been line noise at all. It may have been something further along the chain (between the ISP and BT). But the graph that I have from my ISP seems to suggest line noise, as there is a gradual half hour onset of packet loss before the disconnects start happening.

I would recommend in your case setting up a ping monitor and get some graphs of what is going on. If you see a gradual onset of packet loss leading up to a disconnect, line noise is probably the culprit.

I have a freind who lives in the states and loss of pppoa sessions are a regular occurrence with AT &T bellsouth, it could be a radius server issue

Edited by tommy45 (Thu 08-Sep-11 22:30:02)

That is very interesting, thanks for sharing your experience. Mine went off again at around 7pm BST tonight and since I've connected a brand new micro filter directly to the test socket, I can safely rule out my internal wiring and other local factors.

Like you, I can't understand why the line doesn't resync to a lower speed to maintain noise margin because sometimes it takes a good few minutes before the line is able to reconnect whereas in the past a resync would have the line back up within a minute or so.

I might try what you suggest and track packet loss. I think I've got an old telnet script somewhere which I have used in the past to track ADSL line stats. I can use it to track noise margin against time.

Thanks,
Craig.

No they just gave me the standard script on what I needed to do before a line fault could be suggested.

I'm pretty sure it is a BT or Zen issue ( maybe a Radius issue as suggested by another poster ) . I have taken great care to have as perfect a setup as possible with my broadband in my house so although I understand the need to rule out issues at my end, I didn't expect to find anything wrong with my kit.

On 21CN, where is the split in responsibility between BT and Zen? Anyone know? Who owns the radius server?

For reference it can't be a RADIUS issue as RADIUS is only involved for authentication and accounting. Once a PPP session is up RADIUS is no longer in control, so couldn't be the cause of the drops.

It does sound, to me, like an ATM packet corruption issue - not sufficient for the sync for fail but bad enough to cause the PPP to disconnect. I suffer from similar issues, but I always put it down to my TG585 overheating regularly. I'll have to look to see if the eval TG582 I have is showing similar problems.

Your best option is to discuss this with TS.

Thanks Jander, much appreciated.

I'll get back in touch with TS now that I've carried out some of the requisite tests at this end. I've gone through similar intermittent issues (albeit affecting sync not PPP) in the past with Zen and they have always turned out to be BT issues. On one occasion a distant neighbour had a faulty Sky box which was bursting out RFI and affecting half my street. It was only happening sometimes though so was difficult to track down. I've also heard of street lights causing interference too although the timing of my problems doesn't coincide with street lighting.

Cheers,
Craig.

Hi,

Just a quick update. I spoke to Jon in tech support this morning and he was very helpful. I think the options for investigation probably open up quite a bit once the initial steps have been carried out. Anyway, Jon sent me a graph showing my line uptime/downtime in 15 minute blocks over the last 40 days or so. It was very interesting as it showed a notable increase in dropouts starting from the evening of 31 Aug. It also showed some subtle patterns of dropouts at certain times of day. Not clear patterns as such but certainly clusters.

I was talking to my next door neighbour tonight and we virtually asked each other at the same time whether the other was having broadband issues. When I told him I started having issues on 31st August and that I had three mornings in a row where it failed at 08:40am and that it seemed to last for 5 - 8 minutes at a time he started to laugh! It turns out his wife has bought a Power Plate type exercise machine and they used it for the first time on (you guessed it) 31 Aug! A typical session is 6 minutes and she uses it at the same times as I have been seeing broadband issues! They also have broadband issues and their router loses sync completely. I've just had an email from them to say that they tried tuning an AM radio in to 612kHz (as suggested by Jon earlier) and sure enough, they can hear a lot of interference from the machine. Even worse, the machine was recommended to them by their other neighbour (two doors from me) who has had one for a month or so. They are round there just now with their AM radio comparing interference patterns to establish if it is a design fault or a specific fault on their machine. Either way I think a solution may be about to emerge!

They tried running the machine tonight and my line stayed up but I think that may be because I'm running from the test socket. Normally I would have my alarm connected to the line (via the faceplate filter) and it has a standard phone cable running up the inside of the wall into the attic. That would make an ideal aerial for an AM signal! So, I think tomorrow I'm going to reconnect my faceplate filter and internal wiring and then get him to put his machine on and see if it kills my signal. If it does then I might offer to loan him a pair of wire cutters to cut the plug off his machine!!! Or just send it back as faulty and get a refund - I think the novelty has worn off anyway...

So, there you go - problem probably caused by indicative pickup from a large electric motor!
Cheers,
Craig.