Bad connection

[dunkers]

Is there something up this evening? I've had to switch to my Entanet connection in order to post this

There are two problems I seem to be having: firstly tracerts would fail in interesting ways to various places, and trying to post messages on a BBS, for instance, would sometime be fine and other times very very slow. Some sites I can reach whereas others, at the same time, I couldn't.

Secondly, my connection seems to be down quite regularly for up to a minute at a time. You can see from this chart that my normal 10-15ms pings have taken a strange dive today. The packet loss bars are misleading - sampling is happening at 5 minute intervals here, so I could lose the connection and so long as it's back before the next sample it won't show up.


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[Sebby]

You mention an Entanet connection; that means you have another line for that service? Two lines can be completely different. Could you provide a bit more information about your setup on the IDNet line, and also post your router stats?

[dunkers]

Wow! You replied there before I'd finished posting 

Router stats could be tricky you want anything deep - it's an Edimax AR-7084A and the webificated interface has:

Code Select Expand


Downstream Upstream
       SNR Margin: 5.5 9.0 db
Line Attenuation: 46.0 31.5 db
        Data Rate: 6144 832 kbps


The IDNet line used to be Nildram and had few problems (other than Pipex and then Tiscali taking over). It used to run a Vigor 2600 and stayed up for months at a time, although this was with a fixed 2MB service. When I changed to IDNet about 4 weeks ago I left the Vigor as it was. On migration, I gaine interleave which I asked support to remove, which they did. All seemed OK except that there would be strange pauses periodically, and I put this down to the Vigor running out of steam on a MAX line, hence the swap to the Edimax.

I had this sort of trouble a week or two back and then it cleared up for a week and I got an uptime of 5+ days.

[Sebby]

Okay, the stats look good. You've got a very decent sync for a 46dB line. The SNRM is healthy too, so there's no issues in this department.

Does the Edimax provide any log of errors? I wonder if your line could be suffering from high errors now than interleaving has been turned off.

You could do a BT speed test too and post the results. It's always useful for us to see, though perhaps not so much in this case.

Do you have a NTE5 master socket? If so, could you remove the front plate and connect the router to the socket behind (the test socket). Then see if things are any better in terms of pings and pages loading. Again, I don't think this applies so much in this case as your stats look fine, but it's always good to check.

Lastly, it might be worth changing the microfilter/RJ11 lead if you haven't already. I'm sure it's not that, but it's good to eliminate everything if possible.

If none of the above makes any difference, I think it might be one for IDNet, who'll perhaps have to raise it with BT.

[dunkers]

The log is typically along the lines of:

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1/1/2000 6:0:27> MPOA Link Down
1/1/2000 6:0:27> SNMP TRAP 2: link down
1/1/2000 6:0:43> netMakeChannDial: err=-3001 rn_p=804649f8
1/1/2000 6:0:51> Last errorlog repeat 1 Times
1/1/2000 6:0:51> MPOA Link Up
1/1/2000 6:1:16> ppp_ready: ch:804764d0, iface:803f9090
1/1/2000 6:1:16> SNMP TRAP 3: link up
1/1/2000 6:1:16> Accept() fail
1/1/2000 6:1:16> Accept() fail
1/1/2000 6:7:50> MPOA Link Down
1/1/2000 6:7:50> SNMP TRAP 2: link down
1/1/2000 6:8:14> MPOA Link Up
1/1/2000 6:8:40> ppp_ready: ch:804764d0, iface:803f9090
1/1/2000 6:8:40> SNMP TRAP 3: link up
1/1/2000 6:8:40> Accept() fail
1/1/2000 6:8:40> Accept() fail

The date I forgot to set after resetting the router earlier to see if that would fix things.

The speed test nearly always comes out great. I had it very low once, but every other time it's impressive and implies the full line ability is utilised.

The master socket isn't like that one, but has separate sockets for phone and modem. I'll whip out the phone and see if that helps any. Thanks for your help/interest

[Mytheroo]

5.5db snr downstream is right on the cusp, if you have some extra noise at points this will cause the loss of sync. Have been doing alot of testing with my parents and it was dropping all the time with 5-6db. (6km line 61db att.)

See if you can get it changed to 9db snr. Is it connecting with a.gmt or ADSL2 do you know?

[paulsmith109]

I `ve also seen ping variations on my connection. By disconnecting and then reconnecting PPP (no loss of synch) I can regain a steady ping of 11-12ms. Do you connect via the `gw5` realm by any chance?

[J!ll]

      dunkers

[Ray]

Dunkers  and have a welcome

[Rik]

Hi Dunkers and welcome to the forum.

I also had to dump a 2600 on moving to Max, it just didn't seem to be able to cope. Sebby has taken you through everything I would normally suggest, I just wonder if it's possible for you to extract the error count from the router? Usually, if interleaving gets turned on, it's for a reason, and it may be that you're getting bursts of noise, and with it errors, which is causing the problems you are seeing.

If you're satisfied you've eliminated your own equipment and wiring, give support a call and they can test the line and, if necessary, get an engineer out to you. Be aware, though, that if he/she finds the fault on your side of the master socket, they will raise a charge of £160+.

[Simon]

Hi Dunkers, and 

[dunkers]

Thanks for the welcome, people  8)

@Mytheroo: On checking this morningafternoon the SNR is reported as 8.5 down and 9 up, with basically the same attenuation. I wonder if that's because I unplugged the phones last night... For connection, all it says is g.dmt on the webcon front end.

@paulsmith109: Yep, it's the gw5 realm. I'm hesitant to ask if that's good or bad  . I did try a router restart when there were obvious problems, and that didn't affect anything that I could see.

@Rik: The ADSL error count on the router stays at 0 whatever seems to be happening. It doesn't inspire confidence in the report, though - the Vigor would show corrected and uncorrected errors, as you know. <pokes around a bit...> Ah! I get this from the telnet interface:

Code Select Expand

near-end FEC error fast: 0
near-end FEC error interleaved: 0
near-end CRC error fast: 972
near-end CRC error interleaved: 0
near-end HEC error fast: 1424
near-end HEC error interleaved: 0
far-end FEC error fast: 0
far-end FEC error interleaved: 0
far-end CRC error fast: 12
far-end CRC error interleaved: 0
far-end HEC error fast: 6
far-end HEC error interleaved: 0
Error second in 15min           : 2
Error second in 24hr            : 429
Error second after power-up     : 429
ADSL uptime     7:50:31

Means nowt to me, and I think the line is OK at the moment anyway.

Something I haven't mentioned is that I get a similar problem on the Enta line. I didn't mention it before because that do it at different times (that is, one will be fine and t'other a bit dodgy), and the IDNet line has only started doing it since I dropped Nildram. Er... and it just occurred to me that Nildram wasn't MAX. Doh!

So... given that, does it sound like a problem between the pole and premises? BT have checked the Enta line and found nowt wrong from the exchange, and want the £160 to come out and poke around here. However, a client also on Enta had dropping connections and got the full BT call out thing but they reported no fault and they just basically put up with the drops. A month or so ago they lost the line completely for 6 days and BT eventually found a problem with the incoming pairs (there was another problem as well, but that's something else). The pairs were fixed and the connection has been up ever since. The point I'm getting to here is that I could easily see BT coming out and finding nothing wrong but stiffing me for the £160 (or £320!) all the same.

[Rik]

Your error count is quite low, and interleaving is not on, so the line looks fundamentally sound. If the Enta line is doing something similar, it would suggest an external noise source or a line fault - the problem is going to be finding out which it is from your side of the connection. I'd suggest contacting support, letting them know what is happening and that it affects the other line too. They can they test and see what's visible to them. Possibly, if you report your Enta line too, the response from them will enable a sort of 'triangulation' to try and determine what is happening. Ultimately, though, you do risk being stuck with a hefty bill - not an ideal situation. I do know that IDNet will try to ensure that doesn't happen by eliminating your side of the master socket as far as possible.

[dunkers]

Yes, I think that's going to be inevitable now. My reason for posting originally was mostly to check that it really is a problem here (i.e. that no-one else is suffering, as happened a couple of weeks ago). I'd really hate to spend an evening swapping kit out if unnecessarily . Your diagnosis is much appreciated 

[Rik]

Have you tried wandering around with a de-tuned MW radio, btw. Follow the path of the phone line and see if the noise increases anywhere.

[dunkers]

That's clever idea! I can't at the moment 'cos I'm deaf and my partner is AWOL at the moment, but I'll get her to try it when she gets back.

[Rik]

Sorry to hear about that, Dunkers, it must make life difficult for you at times.

ADSL operates in the MW band, so if the radio picks up noise, your ADSL will be doing too. Take the radio off tune, to an area of the dial between stations, then it will latch onto any signal in the spectrum.

[Sebby]

For a 46dB line with interleaving off, the line looks to be great, so I'm at a bit of loss. Rik's suggestion of a detuned MW radio is the best way of finding a noise source, though I must admit that I'd be surprised if there was a source of noise around as the sync is so good for a 46dB line!

[Rik]

Me too, Sebby, but it's worth a try.

[Sebby]

Indeed. Anything's worth a try in these mind-boggling cases!

[Rik]

It really comes down to try everything you can to prevent BT raising a no fault charge. After which, offering a sacrifice to the gods of ADSL sometimes works. 

[dunkers]

It's back to very bad again tonight, and I noticed that the SNR was 4.5 (now at 5.5). How would I go about getting it pinned at 9? Just talk to support?

[Gary]

The snr is not hugely bad for this time of night, each 3db increase reduces your overall speed as far as I am aware, I have connected at 3db at night with my old router and not had any speed of throughput issues though

[dunkers]

Oh well. Seemed a reasonable straw to clutch at the time

[Sebby]

4.5dB isn't bad for night, as Gary says. If you sync during the day at 6dB (the default target) then it's going to decline at night. If you sync at night, you'll have a SNRM of 6dB at night and higher in the day.

But, like I say, your stats really do appear to be fine. You could get your target SNRM upped to 9dB, but I don't think it'll help, unless of course we find out the issue is errors (thought we've seen that your error count is quite low, unless your router is reporting inaccurately).

[Rik]

Hi Dunkers

Everything is pointing at a BT-side issue at the moment, so once you've had a chance to do the MW walkabout, I'd suggest you get support to take a look at the line and see what they find.

For anyone interested, if you want your target margin pinned at a higher level to improve stability, just ask support, and they can get it done. I have mine at 9db because the line quality is poor.

[Simon]

Mine still seems to be pinned at 18db. 

[Rik]

Impossible, Simon, the highest official rate is 15db. If your router re-syncs at night, it will get a lower speed for the target margin than it will during the day. I currently have an 11db margin, which drops back to 9db at night, for example.

How stable is your connection, have you been able to hold the line for 14 days or more?

[Simon]

The connection seems to be stable, and here's what I can find:

Current Rate:         3776 kbs         448 kbs
Max Rate:       4912 kbs       836 kbs
Current Connection:
Current Noise Margin:       17.0 dB       18.0 dB
Current Attenuation:       34.8 dB       18.0 dB
Current Output Power:       19.5 dBm       12.1 dBm

[Rik]

Looks like you've only reached 11.5 days, Simon, hang one for another four or so, then re-boot.

[Simon]

OK, that was a manual reset, which I didn't think would have any negative effect.

[Rik]

Reset of the PPP session or a full re-boot. The latter would have counted.

[Sebby]

As Rik says, the last re-sync was about 11.5 days ago so give it another 4 to be on the safe side.

With regards to the 18dB margin, it must be 15dB. Remember that if the noise reduces since the sync, the SNRM will improve, regardless of the target.

[Simon]

Reset of the PPP session or a full re-boot. The latter would have counted.

No, it wasn't a full reboot.  Just a DSL Link reset.

With regards to the 18dB margin, it must be 15dB. Remember that if the noise reduces since the sync, the SNRM will improve, regardless of the target.

So, why does it say 18dB? 

[Sebby]

So, why does it say 18dB? 

Okay, so BT assign you a target of 15dB. You plug in your router and it negotiates with the exchange. What will happen is that the sync will be a figure such that the SNRM is 15dB. So your sync is going to depend on line conditions at that point in time.

Say you did that at night (the noisiest time). The next day, the noise will have reduced. So although your target remains unchanged, the actual SNRM can move either way after you have sync'd.

You could re-sync now and your new sync will be different to achieve a SNRM of 15dB. But then come tonight, you'll find that your SNRM will actually be lower than 15dB.

Don't try it though as you're trying to stay sync'd for 14 days.

[Gary]

Okay, so BT assign you a target of 15dB. You plug in your router and it negotiates with the exchange. What will happen is that the sync will be a figure such that the SNRM is 15dB. So your sync is going to depend on line conditions at that point in time.

Say you did that at night (the noisiest time). The next day, the noise will have reduced. So although your target remains unchanged, the actual SNRM can move either way after you have sync'd.

You could re-sync now and your new sync will be different to achieve a SNRM of 15dB. But then come tonight, you'll find that your SNRM will actually be lower than 15dB.

Don't try it though as you're trying to stay sync'd for 14 days.

which he cant as we have the engineering works this week unless that does not effect sync just ppp of course

[Rik]

I have a feeling it will drop PPP sessions, not sync, Gary, but that's just a guess.

[Gary]

I have a feeling it will drop PPP sessions, not sync, Gary, but that's just a guess.

I hope so Rik, if its been like the other lots of work done buy BT the it should be PPP, odd thing is I checked my exchange for listed work after my PPP session drop the other day and no work at my exchange was listed, saying that its probably just BT not giving the when and wears out for it correctly

[Rik]

Last year we were able to get a list of exchanges and dates. I haven't seen one this year.

[Gary]

Last year we were able to get a list of exchanges and dates. I haven't seen one this year.

BT probably can't guarantee their engineers will wake up in time from naps in from mobile phone black spots to complete the work

[Sebby]

[dunkers]

Thanks for the info peeps. I think I'll try having it pinned at 9db just to be sure that doesn't fix it (or maybe it does and that's job done!).

Er.. why would it be expected to get worse at night?

[Rik]

ADSL operates in the MW band, so at night, when radio waves travel further, there's more interference (the old Radio Luxembourg effect). As a result, you'll tend to see the noise margin drop during the hours of darkness and recover as it gets light. There is also an increased incidence from street and other lights.

[Gary]

There is more noise at night Dunkers, street lights etc can all cause line noise, it always dips at night time, I would honestly say that a sync of 4.5 is not bad for night as long as you go up to about 6db in the day which is your target, if you increase your snr by 3db you lose about 1MB on your sync rate for each 3db increase if I remember correctly

What Rik said 

[Mytheroo]

just to add, my mom's was 6db snr on 60db att. line, sync was lost every 2-30 minutes. Is now very stable at 15db snr target.

It all depends on the variance of noise I suppose, if noise bursts are 8db then u need 12-15db snr to survive the burst. If noise burst is 0.5db then you could probably sync with a 4.5 snr and survive it

[Gary]

just to add, my mom's was 6db snr on 60db att. line, sync was lost every 2-30 minutes. Is now very stable at 15db snr target.

It all depends on the variance of noise I suppose, if noise bursts are 8db then u need 12-15db snr to survive the burst. If noise burst is 0.5db then you could probably sync with a 4.5 snr and survive it

60db is a very long line though, Dunkers has an attenuation of 46db which is less than myself so I would have thought 4.5snr would be fine.

[Rik]

I agree with Myth, Gary - it depends on the noise. Because my line is prone to bursts, I have the target margin pinned at 9db to achieve stability. I could step up a profile if I had it at 6db, but I'd be forever re-synching (and probably dropping back the profile step I had gained).

[Gary]

I agree with Myth, Gary - it depends on the noise. Because my line is prone to bursts, I have the target margin pinned at 9db to achieve stability. I could step up a profile if I had it at 6db, but I'd be forever re-synching (and probably dropping back the profile step I had gained).

Its odd though that Dunkers has such noise on his line, but saying that it could be anything, living in the sticks does have some advantages it seems then, about the only one though, I just thought having such an attenuation of 46db he should not really have to have it pinned at 9db but of course environmental issues vary form place to place 

[Mytheroo]

The analogy I gave my Dad was, it's like building a tunnel to the exchange that you want to drive a car down, but you only have a set amount of bricks.

If the exchange is a long way away, then your tunnel has to be narrower, and you can't fit your Rolls Royce (8mbit) down it, you can just about fit an Astra (4mbit), and a Seicento (2mbit) fits fine.

Also, noise on the line is like the walls flexing in and out, so even though the Astra fits normally, occassionally the noise (flex) will trap the car and you lose sync, so you set the gap between car and tunnel to be higher (target SNR) and only try to send the Fiat.

[Gary]

I must admit its a great analogy, but you picked some awful cars, I have 4mb at 49db with a 6ish snr and its NOT an Astra being driven here

[Rik]

I'll never be able to discuss noise margin in the same way again.

[Inactive]

Of course the Fiat will break down and jam the tunnel, still Fiat + Italy = Tiscali...

[Mytheroo]

I actually own the bad Fiat  

good news is it has fitted in all tunnels so far  

[Gary]

I actually own the bad Fiat 

good news is it has fitted in all tunnels so far 

they fit in skips to 

[Inactive]

I actually own the bad Fiat 

Whoops Sorry.. 

[Mytheroo]

Of course the Fiat will break down and jam the tunnel, still Fiat + Italy = Tiscali...

Very Truissimo. Luckily I do all the work on it myself, which keeps me in full time employment  

[Inactive]

they fit in skips to 

They not only fit in skips, they are skips when upturned.. 

[Inactive]

Very Truissimo. Luckily I do all the work on it myself, which keeps me in full time employment 

[Rik]

Very Truissimo.

I thought that was a dessert! 

[dunkers]

Hmmm... we happen to have a Passat and a Civic here. Not sure which goes with what line, though.

Spoke with support who say my SNR was 9db (which it was at the time) so therefore my target must be set to that. Didn't stop the line dropping, but I don't know what the SNR was at that time. Hmmm.

[Rik]

Did they test the line?

[dunkers]

BT or support? I don't actually know either way.

[Rik]

Support would normally have tested the line to see if they could identify a problem. What did you actually ask them?

[dunkers]

Me:

Hi, I'm having intermittent problems with my connection. Could I have the down SNR pinned at 9db for a while, please, so I can rule this out as a potential cause/fix. I understand that this could reduce my bandwidth.

Them:

Your SNR margin is already at 9db, suggesting this is the current target
for your circuit.

[Rik]

Ah, OK. It might be worth going back and reporting the instability, asking them if they could take a look at the line for you (a woosh test).

[dunkers]

Yes, you're right. However, I didn't want to start an actual investigation because when it inevitably gets to BT needing to come out they can't do that until next month (for access reasons here, rather than them). It would be tricky to sort of put it on hold if/when it gets to that point, so I was holding off until I can follow through (fnarr). Also, it seems  reasonable to think the same or similar problem afflicts both lines, so I'll probably need to coordinate Enta and IDNet to have 'em both looked at by the same engineer.

[Rik]

Sounds like a plan.