[WXC/VFX] Frequent disconnection

Forums › One New Zealand (including Vodafone, WxC, Farmside) › [WXC/VFX] Frequent disconnection

Niel

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#14067 13-Jun-2007 13:53

My DSL-502T log shows the ADSL line disconnects frequently. It used to be 1 or 2 times a day, the other day it was more than 5 times. It says the carrier is lost and 10 seconds later it is up again. Earlier this week it happened almost exactly every hour for about 4 or 5 times in a row. Also, the sync speed can vary anything from about 6500 to 5200 bps. The SNR sits around 13dB. Can get more data if it would help, not at home at the moment.

I am in Pakuranga about 1km from the exchange. There are ADSL2 junction pillars on both sides of our road, however I found out that Telecom provides (speed limited) ADSL2 connections only to new Telecom customers and I'm with XNet. Although there is an ADSL2 junction point on my sidewalk, my phone line still goes to the other side of the road and appears to be connected into an old junction box. My modem definately can negociate only ADSL_G.dmt Annex A, nothing else.

When we were on dial-up we used to be able to connect at 48k, but since the overhead line was ripped off 3 or 4 years ago the connection speed slowly dropped until we could not connect faster than 32k. It was a fault in the junction box, most likely water entered the cables.

It is not a fault in the modem, nor is it related to heat in any way. The wiring in my home is fine, and I'm using a central splitter. Any suggestions as to how I can get this sorted? I am using the latest NZ firmware. I would suspect the phone line outside my home, but surely Telecom tests the line for damage when they switch you over to ADSL? We switched 2 months ago.

Thanks for any help.

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maverick

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#74515 13-Jun-2007 14:32

I will have one of our Support People contact you Niel, since you are a VFX customer as well , let me see what we can do

Yes I am a employee of WxC (My Profile) ... but I do have my own opinions as well

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neilinnz

165 posts

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#74519 13-Jun-2007 15:16

Niel,

I've had this problem before with my D-Link 502T both in Auckland and in Nelson so it doesn't seem to be location specific. I've tried 2 modems too so it wasn't the modems fault.
In both cases to fix it I had my ISP turn interleaving on (I think? maybe they switched it off, anyway they changed it from the default setting).
Once that is done configure your modem to use the ADSL (ITU G.992.2) setting found under Advanced and then ADSL.

There is a downside in that your download and upload speeds will be limited, mine are currently at 3616 and 512 which are fast enough for me.

Since changing that setting I went from between 5 and 20 disconnections a day to none.

I would guess a lot of people get these disconnections but they just don't realise, if they are just surfing the web and it reconnects within a minute then they'll just be assuming the internet is 'going slow'.
I have to have a solid connection for video chats with the UK and for a VPN connection.

I hope this helps.

Neil

Niel

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#74528 13-Jun-2007 16:45

Cameron at WxC phoned me and we spoke for 25 minutes on my mobile, what a 5 star service! (And it paid off for them as well, I'm telling my friends at work, already got one guy wanting to sign up!) We've got one or two ideas, but I am on a new exchange and the signal quality is good and there is no clear reason for this to be happening. Will post back whatever we find...

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Niel

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#74843 15-Jun-2007 17:48

It seems to be stable if I set the ADSL mode to ASNI T1.413, it was on G.dmt. I have tried all the ADSL2+ modes, but they don't work. Cameron (at WxC) said I am definately on an ADSL2+ exchange and some circuits are already enabled with sync speeds around 18Mbps, but it appears my line is just not yet turned on for it. Will see how it goes with the line stability.

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Niel

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#74895 16-Jun-2007 11:47

Spoke too soon... After 1 day the DSL-502T started disconnecting again. I've noticed my 13dB SNR dropping to 6 dB this morning and then gone up to 10 and down to 8 and up to 12, all over the place. My old DSL-302G was stable for 2 days so I have switch back to that. The problem appears to be the modem itself.

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Trkstr

23 posts

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#75045 18-Jun-2007 17:27

What kind of speeds are you getting on your old modem?

Cos if your situation is similar to what i have, it may be impossible to fix just changing modems.

I had the same variable SNR scenario happening. Starting at about 12, then dropping to 3 when there is traffic, and then back up to 7 and then dropping out and reconnecting after about 20 minutes but a lower speed.
At this lower speed, the SNR was higher and the same modem was able to hold the connection for more than a day.

I have been advised by some of the wise people here at the Geekzone forums that this may be due to cross-talk in the lines, and there isn't really much that can be done about that.

Don't worry i feel your frustration as well. I'm now stuck with 1mbit internet when i paid for fullspeed up and down...

Niel

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#75064 18-Jun-2007 18:46

The old one sync at about 6.5Mbps, the new one at about 7.5Mbps but 3dB lower SNR. I have a central splitter, and now have also replaced the old long phone wiring with a short new wire. I can still see dips in the SNR, and it is not me downloading anything. Every time it disconnects it will reconnect automatically after 10 seconds. That is okay for internet browsing, but not for VoIP.

A friend at work also had lots of disconnections on his D-Link, be switched to something else which apparently pings the server every 10 minutes with a keep-alive signal and says he does not get any disconnections any more. Will ask him what he has, but he is convinced D-Link is one of the worst modems available.

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Trkstr

23 posts

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#75357 20-Jun-2007 17:09

Usually i find that i connect at a maximum of about 5mbit with a SNR of about 12 to start with. But then when there is traffic, this drops down to about 5 sometimes 2, sometimes the connection just drops out entirely. I understand that faster speeds = lower SNR in most cases. A lot of people have said it is the hardware at fault.
I first noticed this problem in my old WAG54G which served me well when i had 2mbit. But wasn't able to handle the new speeds.
Then i moved onto a Netgear DS834G which seems to handle ok. It can maintain a connection of about 1.1mbit for extended periods of time with a reasonable SNR. Anything faster and the SNR dies.
I have also tried an old Dynalink which seems to have the same SNR drop problem.

This may be a safe conclusion that it is definitely my line. But, is it possible that xnet could be doing something at their end to cause this? I never really had any problems of this nature until i switched from ihug.

Niel

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#75467 21-Jun-2007 08:57

It is not XNet and it is unlikely to be Telecom (although we all would like to blame them). The line will be fine as long as the wires are installed properly and not loose in the connections.

Another, lengthy search on the internet brought up something:
http://forum.exetel.com.au/viewtopic.php?=&p=151201

RFI:
I have redone all the wiring in my house, and the modem was stable for just under 2 days... Started dropping out again and reconnect after 10 seconds. After finding the link above, I am convinced this guy is on to something. I'm using a wireless router and also have a DECT phone close to my modem. Then there is also this huge old 21" monitor besides the modem. Definately a better solution is having the modem and WiFi in one box, because then it is designed to work together and mostly eliminates one source of RFI. My connection drops any time of the day/night, and even with the PC off. So I can eliminate RFI from the PC as a source (still can be monitor in standby, DECT, or WiFi).

LCP:
My modem stays up for about 2 days and then suddenly starts dropping connections. This tells me that it is more likely to be loss of LCP packets due to a bug in the older Linux PPP driver (many modems run Linux as an operating system). Perhaps the problem is something like a counter overflows and corrupts a byte in the modem, and so will run fine for some time after a modem reset, and then start disconnecting randomly.

The SNR dipping points towards RFI, but would be expected to be more frequent and periodic. Not sure if lost LCP packets are reflected in the SNR, but the writeup suggests that the driver reports packets as sent but actually at random they are not and it is actually the exchange not receiving the packets that causes the disconnection.

So for me the next test is to move the modem away from anything else, disable WiFi, turn off the DECT base station, and remove batteries from the DECT phones. Will let you know in a few days what happens. (Oh, I just remembered I also have a wireless alarm system...)

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Niel

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#77235 7-Jul-2007 11:48

Since we got ADSL2+ enabled last week for all connections in Pakuranga, my modem has disconnected only once in a week. This week my SNR also improved from 10dB to 14dB, and appears to be very stable (previously would jump all the time). My connection speed with the old 502T (updated long ago to the latest firmware which supports ADSL2+ protocol, but hardware limits speed to 8Mbps max) connects at about 7.5 Mbps on the ADSL2+ profile which is as good as it gets with these old models. Telecom is right now actively doing experimentation with firstly their modems, but also others (I think 17 it total), with results due for release (if it is not yet). I suspect that they were still tweaking settings on the new ADSL2+ exchanges, and now that it is launched they made adjustments for everyone on those exchanges.

As said, my modem is now so stable that I am almost impressed with the 502T. It can also be that now with ADSL2+ enabled for all, my modem is stable due to significantly less crosstalk from other users.

Anyway, would be good to get feedback from others as well. If ADSL2+ is enabled on your line, is your modem suddenly stable?

You can never have enough Volvos!