Connection dropout

[samp]

Hi All

I've been with Idnet for around 3 weeks and am getting intermittent connection problems. The most part the connection speeds are good and I get good warcraft latency (typically ~70ms). However my connection will often completely drop, sometimes the net will be completely unresponsive for 20-30 seconds and then return to normal, occasionally the router will disconnect (reporting LCP down) and I have to manually click reconnect through the router to get it back up. It seems much worse at peak times. Last night for example the line was dropping out every few minutes until about midnight when it all worked fine. Throughout these dropouts the connection from PC to router is fine, the router stats for tx/rx packets barely moves. I've included some stats below

Windows XP (sp2)
Netgear DG834PN router
Stats from the router:
connection speed 6624 down 448 up
line attenuation 32db down 14.5 up
Noise Margin 5.8db down 22.0db up

I've yet to attempt using the NTE5 master socket as that involves moving furniture. My main question is the downstream noise margin of ~6 bad? Any other ideas would be greatly appreciated


Sam

[Rik]

A Max service has a default noise margin of 6db, so you're seeing the right results. It sounds, though, as if you may be getting some sync problems. Take a look at this sticky, and see if it helps you get more stability. If it does, the problem lies with your wiring, if it doesn't, call IDNet support and they can get an ADSL engineer out to you (don't report a fault via 151, that's for voice only).

Note, though, that if the engineer find a fault after the master socket, ie in your wiring, you may be charged for the visit, so it's best to work right through the the sticky before making the call.

[samp]

Thanks Rik I will give the info in that sticky a try.

[Rik]

Let us know how you get on, and if anything's not clear, yell.

[samp]

Hi

I'm now connected to through the microfilter to the nte5 behind the faceplate.

As per the norm my connection was perfect until after 6 when it consistently drops every 5-20 minutes. I also noticed my noise margin had dropped to ~3.0db. I rebooted the router, noise started at 5.6 and is now slowly dropping to <5. I've included some of the log from my router.

Any ideas on what could cause such noise/drop outs only at peak times?

Sam

Sat, 2007-03-17 14:45:08 - Receive NTP Reply from time-g.netgear.com
Sat, 2007-03-17 14:43:31 - Router start up
Sat, 2007-03-17 14:43:32 - Router start up
Sat, 2007-03-17 18:21:41 - LCP down.
Sat, 2007-03-17 18:21:49 - Initialize LCP.
Sat, 2007-03-17 18:21:49 - LCP is allowed to come up.
Sat, 2007-03-17 18:22:49 - Initialize LCP.
Sat, 2007-03-17 18:22:49 - LCP is allowed to come up.
Sat, 2007-03-17 18:23:37 - CHAP authentication success
Sat, 2007-03-17 18:50:38 - LCP down.
Sat, 2007-03-17 18:50:47 - Initialize LCP.
Sat, 2007-03-17 18:50:47 - LCP is allowed to come up.
Sat, 2007-03-17 18:51:47 - Initialize LCP.
Sat, 2007-03-17 18:51:47 - LCP is allowed to come up.
Sat, 2007-03-17 18:52:47 - Initialize LCP.
Sat, 2007-03-17 18:52:47 - LCP is allowed to come up.
Sat, 2007-03-17 18:53:19 - CHAP authentication success
Sat, 2007-03-17 18:53:47 - Initialize LCP.
Sat, 2007-03-17 18:53:47 - LCP is allowed to come up.
Sat, 2007-03-17 18:54:47 - Initialize LCP.
Sat, 2007-03-17 18:54:47 - LCP is allowed to come up.
Sat, 2007-03-17 18:55:48 - Initialize LCP.
Sat, 2007-03-17 18:55:48 - LCP is allowed to come up.
Sat, 2007-03-17 18:56:48 - Initialize LCP.
Sat, 2007-03-17 18:56:48 - LCP is allowed to come up.
Sat, 2007-03-17 18:57:41 - CHAP authentication success
Sat, 2007-03-17 18:58:41 - LCP down.
Sat, 2007-03-17 18:58:47 - Initialize LCP.
Sat, 2007-03-17 18:58:47 - LCP is allowed to come up.
Sat, 2007-03-17 18:59:09 - CHAP authentication success
Sat, 2007-03-17 19:01:29 - LCP down.
Sat, 2007-03-17 19:01:36 - Initialize LCP.
Sat, 2007-03-17 19:01:36 - LCP is allowed to come up.
Sat, 2007-03-17 19:02:36 - Initialize LCP.
Sat, 2007-03-17 19:02:36 - LCP is allowed to come up.
Sat, 2007-03-17 19:03:36 - Initialize LCP.
Sat, 2007-03-17 19:03:36 - LCP is allowed to come up.
Sat, 2007-03-17 19:04:23 - CHAP authentication success
Sat, 2007-03-17 19:06:23 - LCP down.
Sat, 2007-03-17 19:06:30 - Initialize LCP.
Sat, 2007-03-17 19:06:30 - LCP is allowed to come up.
Sat, 2007-03-17 19:07:30 - Initialize LCP.
Sat, 2007-03-17 19:07:30 - LCP is allowed to come up.
Sat, 2007-03-17 19:08:30 - Initialize LCP.
Sat, 2007-03-17 19:08:30 - LCP is allowed to come up.
Sat, 2007-03-17 19:09:30 - Initialize LCP.
Sat, 2007-03-17 19:09:30 - LCP is allowed to come up.
Sat, 2007-03-17 19:10:30 - Initialize LCP.
Sat, 2007-03-17 19:10:30 - LCP is allowed to come up.
Sat, 2007-03-17 19:11:30 - Initialize LCP.
Sat, 2007-03-17 19:11:30 - LCP is allowed to come up.
Sat, 2007-03-17 19:11:59 - CHAP authentication success
Sat, 2007-03-17 19:15:16 - LCP down.
Sat, 2007-03-17 19:15:24 - Initialize LCP.
Sat, 2007-03-17 19:15:24 - LCP is allowed to come up.
Sat, 2007-03-17 19:15:47 - CHAP authentication success
Sat, 2007-03-17 19:20:44 - LCP down.
Sat, 2007-03-17 19:20:52 - Initialize LCP.
Sat, 2007-03-17 19:20:52 - LCP is allowed to come up.
Sat, 2007-03-17 19:21:53 - Initialize LCP.
Sat, 2007-03-17 19:21:53 - LCP is allowed to come up.
Sat, 2007-03-17 19:22:53 - Initialize LCP.
Sat, 2007-03-17 19:22:53 - LCP is allowed to come up.
Sat, 2007-03-17 19:23:53 - Initialize LCP.
Sat, 2007-03-17 19:23:53 - LCP is allowed to come up.
Sat, 2007-03-17 19:24:53 - Initialize LCP.
Sat, 2007-03-17 19:24:53 - LCP is allowed to come up.
Sat, 2007-03-17 19:25:53 - Initialize LCP.
Sat, 2007-03-17 19:25:53 - LCP is allowed to come up.
Sat, 2007-03-17 19:25:57 - CHAP authentication success

[Lance]

For some reason, it keeps losing LCP, whatever that is! Possibly due to your noise margin dropping too low. If it is doing this while you are connected to the test socket, behind the NTE5 faceplate, that rules out any internal wiring. Perhaps try plugging directly into the test socket without the filter, the filter is used to filter out the telephone signal and lets the Internet connection straight through.

If it happens at the same time each day, have you noticed anything else which happens around the same time? It is possible for a central heating system, for example, to upset a connection in some cases. Likewise, a microwave in use can also possibly upset a connection.

If we are still none the wiser by Monday, it may be worth giving support a call to see if they can offer any help. It may be there is a problem with your line before the master socket, in which case support will arrange for an ADSL trained BT engineer to come out to your house.

Hope this helps.

Lance

[samp]

It certainly isn't a microwave and whilst I doubt it's central heating I will try turning it off tomorrow. I'm guessing the noise margin had only dropped so because I had so many disconnects. My other thought was to mess around with the MTU settings, maybe I'm "getting away" with a certain amount of fragmentation outside of peak times but when the local xchange gets busy it causes enough packet loss to take the connection down. I'm merely clutching at straws here.

Sam

[Lance]

I wouldn't expect it to be the central heating either. It was just a suggestion based on you stating it always happens around the same sort of time.

As far as I know, your noise margin would drop simply because of disconnects, but I may be wrong on this.

The recommended MTU for IDNet seems to 1458. You could be right about the fragmentation at peak time but I don't think this necessarily causes packet loss. However, I think that a high RWIN value could cause packet loss, it may be worth trying to reduce the RWIN, but only if if you believe you are seeing packet loss.

Another thought is have you tried removing the ring wire from terminal 3 (ofter orange/white) in all telephone sockets in the house? Many people have found doing this it removes some noise from the line.

I can't think of anything else that may help, but Rik, who will no doubt be about later, might be able to offer more help.

Lance

[samp]

I've since tried connecting the router directly to the RTE5 port and it refuses to connect at all, despite a couple of reboots.

[Lance]

Prehaps my memory was failing me on that point and I was wrong. Sorry! 

[CaptainSlow]

I'd just add, do not underestimate the power of domestic central heating, it can wreak total havoc on broadband. I know of one that clobbers broadband, phone, TV and radio signals, and that was simply the thermostat/box on the side of the hot water tank having hysteresis for some still unknown reason. Plumber still can't find the fault on that, but we know for sure it is the culprit!

I've also known a fridge that could reset a computer going back many years! (Circa 1984?)

[Rik]

I'm now connected to through the microfilter to the nte5 behind the faceplate.

As per the norm my connection was perfect until after 6 when it consistently drops every 5-20 minutes. I also noticed my noise margin had dropped to ~3.0db. I rebooted the router, noise started at 5.6 and is now slowly dropping to <5. I've included some of the log from my router.

As others have said, this is a fairly common issue. There are many factors at work:

* Increased MW radio propagation

* Electrical appliances including things like central heating, microwaves and fluorescent lights (not necessarily in your house)

* Cross-talk on the cable between you and the exchange as more people come online

* A radio ham in the area - least likely, they know what they are doing

* A rogue Sky box. I've heard reports of them taking out a whole street

Sat, 2007-03-17 14:45:08 - Receive NTP Reply from time-g.netgear.com
Sat, 2007-03-17 14:43:31 - Router start up
Sat, 2007-03-17 14:43:32 - Router start up
Sat, 2007-03-17 18:21:41 - LCP down.
Sat, 2007-03-17 18:21:49 - Initialize LCP.
Sat, 2007-03-17 18:21:49 - LCP is allowed to come up.
<snip>
Sat, 2007-03-17 19:25:57 - CHAP authentication success

The log seems to show a problem with your connection. Normally, I'd expect to see a 'Loss of synchronisation' entry dotted about in there, but you have none, just LCP going down.

From Wikipedia

"In computing, the Link Control Protocol (LCP) forms part of the PPP. In setting up PPP communications, both the sending and receiving devices send out LCP packets to determine specific information that the prospective data transmission will require. The LCP protocol:

    * checks the identity of the linked device and either accepts or rejects the peer device
    * determines the acceptable packet size for transmission
    * searches for errors in configuration
    * can terminate the link if requirements exceed the parameters

Devices cannot use PPP to transmit data over a network until the LCP packet determines the acceptability of the link, but LCP packets are embedded into PPP packets and therefore a basic PPP connection has to be stablished before LCP can reconfigure it. The LCP over PPP packets have control code 0xC021 and their info field contains the LCP packet, which has four fields. (Code, Id, Length, Data)

    * Code: Operation requested: configure link, terminate link, ... and acknowledge and deny codes.
    * data: Parameters for the operation"

If the problem continues at the test socket, and therefore your internal wiring is eliminated (and not causing additional noise), then I'd be inclined to have a word with support. It may be that there is a fault on the exchange side of your BT line.

In the interim, go here and download Routerstats. Run that and it will graph and log your noise, which might be a useful tool for diagnosis.

Note that your noise margin is not affected, directly, by the disconnects. The target is set at the exchange and will remain constant. However, your disconnects are affected by noise - as it increases, your noise margin is eroded until the router can't pick out the signal from the background noise, so it disconnects. A possible cure for you will be to have the target noise margin increased to 9db, to give you more headroom. I did this, and rarely lose sync now. You do lose a little speed, though, but that's better than losing the connection, at least in my book.

[samp]

Using the RouterStats app you suggested I've seen a similar story this evening, the noise level slowly dropped from ~5 to ~2.5 over the course of an hour with disconnects the result. Over the same period the sync speed stayed a constant 6600kbps. After rebooting the router my nose is back to ~6 and the sync speed has dropped to 6000kbps. It's been perfectly fine for about half an hour now.

I'm not entirely sure if thats any use but it seems vaguely interesting that the router would connect at a lower speed but less noise after a reboot. Is it naive/ignorant of me to expect my router and/or the exchange to figure that out without me re-booting the router? Or am I misunderstanding how rate-adaptive connections work?

[Rik]

Max starts off with a target noise margin of 6db. It will then negotiate a connection between DSLAM and router at a speed which can attain that noise margin. Therefore, if the line drops because of a noise issue, the chances are that you will see a lower sync speed. This is not always the case though as it make pick up some frequencies which are less noisy, as a result of which you can get a higher sync speed. It's more common to see a lower speed, though. If you want to sync at the highest speed, re-boot your router early in the morning, if you want to sync at a speed which is likely to maintain stability, re-boot between 8-11pm.

I don't normally see a re-sync on my routers (only one at a time ) unless the margin goes negative. At 2.5db, I'd expect to maintain connection. It may well, therefore, be worth your while moving to a target noise margin of 9db, which would avoid the drop, ie you shouldn't get to less that 5.5db based on the example you quote.

Is it naive/ignorant of me to expect my router and/or the exchange to figure that out without me re-booting the router? Or am I misunderstanding how rate-adaptive connections work?

Possibly. Rate adaptive services work on the principle that they will try and maintain a connection with a 6db noise margin. If noise on the line increases sufficiently for the router to re-sync, it will generally do so at a lower speed, as described above. The noise margin will then be restored to 6db. The system does not allow for upwards movement of sync speed automatically, so if the noise improves, your router will not re-sync at a higher speed.

A re-boot should not be necessary, btw. Normally, a router will simply re-sync.

[samp]

Thanks for all your help on this Rik.

It seems we may be near some sort of conclusion on this, either

(A) I figure out how to get my router to re-sync at lower speeds when the noise margin drops without manually rebooting

(B) As you suggest, move to a target noise margin of 9db.


Sam

[Rik]

The latter is the better option, it works permanently - and I speak from experience!