Loss of Sync

Tacitus · Aug 09, 2009, 11:11:40

This isn't an iDNet problem - I'm with Demon - but there is a wealth of technical knowledge here, so I hope Rik won't mind.

I'm currently experiencing continuous drops in connection - the DSL line usually stays up but the internet connection drops. I can generally identify 2/3 times a day when this happens, but Bangalore tell me it's as many as 8/10. Generally speaking the line stays up - constant DSL light - although sometimes (not always) the line is dropped and it reconnects at a slightly lower speed.

My feeling is that if it was noise bursts forcing the line to drop altogether, the DLM would have pushed speeds right down, which doesn't seem to have happened. They are slightly lower, but not as much as I would have expected if it was happening 8/10 times a day.

Bangalore have me on the swap modems/filters/test socket routine at the moment and won't depart from the script. Just fitted a new NTE5A with a filtered faceplate so it's unlikely, although not impossible, to be that. The modem is currently sitting by the main socket and has been stable for the last hour.

I'm stumped at present for any clue as to where the problem might be. Bangalore are very polite but don't really tell you anything. Any ideas, advice etc will be gratefully received.

Current figures are:
2368 kbps / 448 kbps - sometimes drops to around 2170 kbps, but is otherwise fairly constant in the 2100/2300 range. In the past it has been driven down to 1600 due to storms or heavy noise bursts, but is normally in the above range.

noise margin upstream: 18 db
output power downstream: 16 db
attenuation upstream: 31 db

noise margin downstream: 11 db
output power upstream: 11 db
attenuation downstream: 56 db

Rik · Aug 09, 2009, 11:17:23

It sounds like you're dropping the PPP session, rather than sync, Tac? Does the router log identify that?

Tacitus · Aug 09, 2009, 11:22:53

Quote from: Rik on Aug 09, 2009, 11:17:23
It sounds like you're dropping the PPP session, rather than sync, Tac? Does the router log identify that?

That's what I thought Rik. Unfortunately the router logs tell you precious little

Tacitus · Aug 09, 2009, 11:27:21

There is one curious item that keeps popping up:

08/09/2009 10:41:19 Unsupported/out-of-order ICMP: ICMP(Normal router advertisement) 192.168.2.1 224.0.0.1

I don't have a subnet on 168.2.1 and I'm not sure what 224.0.0.1 is.

Glenn · Aug 09, 2009, 11:31:26

Port 224.0.0.1 everybody

This address means "all hosts" on the network.

http://www.iss.net/security_center/advice/Exploits/Ports/Multicast/224.0.0.1/default.htm

Rik · Aug 09, 2009, 11:35:27

Why your router is responding with that subnet is weird. Is your router set up not to respond to pings?

If the DSL light is staying on, and you're not seeing any changes in sync speed when the drops occur, we have to assume it's PPP. That needs to be investigated by Demon, unfortunately, as you need to know what they are seeing at their end.

Tacitus · Aug 09, 2009, 11:43:59

Quote from: Glenn on Aug 09, 2009, 11:31:26
Port 224.0.0.1 everybody
This address means "all hosts" on the network.
http://www.iss.net/security_center/advice/Exploits/Ports/Multicast/224.0.0.1/default.htm

I'm on a Mac so I wouldn't have thought it was an exploit. Just to be sure I might download a trial of Intego VirusBarrier and give it a run. Rootkits on Macs are not unknown, but I can't see where it would come from, particularly as I run as user, not admin.

Quote from: Rik on Aug 09, 2009, 11:35:27
Why your router is responding with that subnet is weird. Is your router set up not to respond to pings?

Respond to pings is disabled so presumably there is no response.

Quote from: Rik on Aug 09, 2009, 11:35:27
If the DSL light is staying on, and you're not seeing any changes in sync speed when the drops occur, we have to assume it's PPP. That needs to be investigated by Demon, unfortunately, as you need to know what they are seeing at their end.

Thanks for that Rik - it's pretty much what I thought but they won't depart from the script and they don't tell you anything if try to engage them in conversation.

Glenn · Aug 09, 2009, 11:50:44

Tac, it has nothing to do with being on a Mac, it's an IANA reserved address http://www.cisco.com/en/US/docs/internetworking/technology/handbook/IP-Multi.html#wp1020570, if you need something to put you to sleep at night, they you can read the complete document

Tacitus · Aug 09, 2009, 13:32:40

Quote from: Glenn on Aug 09, 2009, 11:50:44
Tac, it has nothing to do with being on a Mac, it's an IANA reserved address http://www.cisco.com/en/US/docs/internetworking/technology/handbook/IP-Multi.html#wp1020570, if you need something to put you to sleep at night, they you can read the complete document

I was thinking of a Mac rootkit/trojan trying to call out to the rest of the LAN. I'm fairly well locked down but I know these do exist even for Macs

Thanks for the heads up though, I'll give it a read - until I fall asleep that is...

I recently updated the firmware and I'm beginning to wonder if it could be that, so I might revert to the previous version and see what happens.

Am I correct in thinking this is more likely to be a problem located either with me or with Demon rather than BT?

zappaDPJ · Aug 09, 2009, 14:44:27

My line continually drops sync as well but there's nothing to show that in my Netgear router log. IDNet can see it, last week I was told it had happened around 20 times in the previous few hours. I'm aware of it happening, especially if I'm running an on-line game. There's no audible noise on my line and everyone is at a loss to know what's causing it. It sounds like the same problem as my DSL light is also green when it occurs.

My gut feeling is that the problem is an exchange issue because I've been swapped to a new twisted pair and the problem still occurs. It's certainly nothing my side of the faceplate because there is nothing my side of the faceplate other than a microfilter which has been swapped. In short, it's a mystery to everyone.

Rik · Aug 09, 2009, 15:09:26

Later Netgear firmware stopped logging loss of sync, Zap. Have you tried running Routerstats for 24 hours?

zappaDPJ · Aug 09, 2009, 15:29:10

Ah! I didn't know that and I stopped running Routerstats a while ago but I run it up now as it would be interesting to see what's going on. Cheers

Rik · Aug 09, 2009, 15:31:04

I reported it as a bug, but they never acknowledged. To me, it was a crazy decision to drop that logging.

Tacitus · Aug 09, 2009, 15:53:02

Quote from: zappaDPJ on Aug 09, 2009, 14:44:27
.... I'm aware of it happening, especially if I'm running an on-line game. There's no audible noise on my line and everyone is at a loss to know what's causing it. It sounds like the same problem as my DSL light is also green when it occurs.

I think for me there are two separate problems. BT have been doing some work in the village so the line's a bit more stable lately, but it still drops most days.

The other is the loss of sync which like you I become aware of but it doesn't show up in the logs unless there's more info via the cli. According to Demon it happens several times a day.

Quote from: zappaDPJ on Aug 09, 2009, 14:44:27
My gut feeling is that the problem is an exchange issue because I've been swapped to a new twisted pair and the problem still occurs. It's certainly nothing my side of the faceplate because there is nothing my side of the faceplate other than a microfilter which has been swapped. In short, it's a mystery to everyone.

No idea whether mine is an exchange problem or whether it lies with Demon. That's the problem with script monkeys you can't get anywhere beyond the script. I've tried swapping the faceplate for a new one (Clarity to an XTE2005) but that made no difference.

I'll have another go with Bangalore - more in hope than any realistic prospect of finding an answer.