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[Berrick]

I had problems with the telephone line recently, adsl would drop a lot and on several occasions at amost the same time on consecutive days for the same amount of time. I had enough eventually and called my ISP after using the telephone would cause the adsl to fail on demand BUT not until I had connected to the test socket and changed the ADSL filter. This made no difference.

Several engineer visits and the ISP is trying to convince me all is well, though they haven't closed the call so I'm not convinced they are sure they have fixed it themselves.

I was wondering if someone could comment on the stats I have included below, they don't look too healthy too me but I'm no expert.

I have tried using DSLstats but it isn't returning anything for my router

ADSL line status
Connection information
Line state   Connected
Connection time   0 days, 1:17:34
Downstream   1,867 Kbps
Upstream   440 Kbps

ADSL settings
VPI/VCI   0/38
Type   PPPoA
Modulation   ITU-T G.992.3
Latency type   Interleaved
Noise margin (Down/Up)   3.7 dB / 13.6 dB
Line attenuation (Down/Up)   67.5 dB / 41.6 dB
Output power (Down/Up)   0.0 dBm / 12.9 dBm
Loss of Framing (Local)   283
Loss of Signal (Local)   43
Loss of Power (Local)   0
FEC Errors (Down/Up)   28923 / 4294967273
CRC Errors (Down/Up)   1227 / 2147480000
HEC Errors (Down/Up)   nil / 9
Error Seconds (Local)   16765

[roseway]

Unfortunately those error figures don't make a lot of sense. They are probably cumulative since the router was last booted, and don't relate to the reported connection time. So it's difficult to assess them realistically. If you reboot the router it should reset the error values, then you can see how they increase over time. Also, you really need to monitor the SNR margin at least, to get a better indication of what's happening. What model of router is it?

[Berrick]

Thanks for the reply.

Try these

ADSL line status
Connection information
Line state   Connected
Connection time   0 days, 0:03:25
Downstream   2,019 Kbps
Upstream   440 Kbps

ADSL settings
VPI/VCI   0/38
Type   PPPoA
Modulation   ITU-T G.992.3
Latency type   Interleaved
Noise margin (Down/Up)   3.7 dB / 12.3 dB
Line attenuation (Down/Up)   65.5 dB / 41.6 dB
Output power (Down/Up)   0.0 dBm / 13.0 dBm
Loss of Framing (Local)   0
Loss of Signal (Local)   0
Loss of Power (Local)   0
FEC Errors (Down/Up)   3632 / 0
CRC Errors (Down/Up)   61 / 2147480000
HEC Errors (Down/Up)   nil / 7
Error Seconds (Local)   1

[roseway]

You can ignore the upstream CRC value because it's exactly the same as it was previously, and it's much too high for such a short uptime. Also it's suspiciously close to 2^31, which probably isn't coincidence.

Apart from that, the figures don't look too unreasonable. You're obviously on the end of a long line and you're getting a reasonable speed in relation to the attenuation. Your upstream speed seems to be capped at 440 kbps, but that's probably the profile which you're on.

The real question is how stable it is now. If you can monitor the SNR margin we can see what the interference conditions are.

Did you mention what router model you have?

[Berrick]

Hi Eric,

Please can you look at the most recent figures.

As you can see both FEC and CRC errors are going up quiet fast, which suggests to me there are still issues with the line, especially when you see that the uplink FEC errors are through the roof again.

Router is a BT HH 2.0a

ADSL line status
Connection information
Line state   Connected
Connection time   0 days, 0:34:01
Downstream   2,019 Kbps
Upstream   440 Kbps

ADSL settings
VPI/VCI   0/38
Type   PPPoA
Modulation   ITU-T G.992.3
Latency type   Interleaved
Noise margin (Down/Up)   3.8 dB / 10.8 dB
Line attenuation (Down/Up)   65.5 dB / 41.6 dB
Output power (Down/Up)   0.0 dBm / 13.0 dBm
Loss of Framing (Local)   0
Loss of Signal (Local)   0
Loss of Power (Local)   0
FEC Errors (Down/Up)   19654 / 4294967264
CRC Errors (Down/Up)   449 / 2147480000
HEC Errors (Down/Up)   nil / 0
Error Seconds (Local)   2

[roseway]

I really don't think you can read anything into the upstream FECs and CRCs. The values are so high that they are not really believable, and the CRC value never changes. The downstream values are quite high but not enormously so for such a long line, and FECs don't matter much anyway (FECs are errors which didn't require retransmission because of the forward error correction).

It may be that there are still improvements which can be made to the line, and certainly if it's unstable you will have good reason to keep pushing your ISP. But the errors on their own don't make much of a case.

Maybe someone else will have a different view.

Unfortunately it seems that none of the normal monitoring programs support the HH 2.0a as far as I can see. BT aren't keen on allowing customers access to performance details of their connections.

[Berrick]

Thanks for your input. Difficult I know as you can only base your replies on the stats I have shown but I do appreciate your insight.

However, my concern about these current figures is fueled with the advantage of knowing the history of this adsl connection which for a long time has been stable, apart from needing an odd router power cycle. The noise margin figure on the download over this time bouncing along around 6 -12 db and was achieving around 2 - 2.4 Mbs download speed (if the speed test site can be believed).

Now though, the line stats I am seeing in the router are all over the place compared to the historical figures (unfortunately I don't have long term records of these ). For example the router now doesn't register the output power on the download which it always has up to now, the Noise margin has never dipped below 6db, interestingly I have seen flappin fiber interfaces log errors as quickly as FEC errors have gone up.

I guess I have had, for the length of the line, pretty good BB until now and I accept that FEC errors don't require re transmission (CRC errors do though) but with my current understanding I have always used FEC's as a gauge to the line quality. Anyways streaming video last night was not a pleasant experience, constant buffering and when it did stream it wasn't fluid, quite jerky.

Another question, are the noise margin figures to do with line profiling or are they SNR figure therefore the lower they are the more noise less signal you get?

If you have got this far in this post, thank you, sorry its quite long want to make sure my understanding is correct.   

 

[roseway]

Another question, are the noise margin figures to do with line profiling or are they SNR figure therefore the lower they are the more noise less signal you get?

Noise margin = SNR margin. It's the difference between the current SNR and a base level of SNR determined by the router manufacturer. Other things being equal, higher SNRM = greater stability but lower speed.

It does sound as though your connection has deteriorated somewhat since earlier times, but unfortunately you're in the area where the amount of deterioration is within acceptable limits as far as the BT systems are concerned (i.e. your speed will be above the fault threshold rate).

Sorry, I don't mean to sound discouraging. What happens now really depends on how much your ISP is prepared to help you.

[Berrick]

HA HA!!

Since my post earlier today I remembered I had a netgear ADSL router. On checking it is a DG834Gv4

So, I put it into debug mode and fired up RouterStats and let it run. The stats it has collected so far are interesting (to a novice) and lend more weight to my concerns.

• SNR on average is at 1db but anywhere between 0db and 3db
• SYnc Speeds are UP 450Kbs, DOWN 2Mbps

During this time we received several phone call and at exactly the same time the Sync speed UP and DOWN dropped to 0.

[roseway]

That's much better - you can collect some useful monitoring data now.

Your SNRM is really too low for stability. You might get away with it, but the error rates will be higher than is desirable. I guess that your target SNRM is 3 dB - are you on an ADSL2+ connection?

The effect on your connection when the phone rings is indicative of a possible line fault. When you say that the sync speed dropped to zero, do you mean that the connection dropped and then immediately reconnected at the same speed?

[Berrick]

A slight correction first, my DG834 is v3 with f/w v4. In my excitement at finding I had a DG834 didn't twig the v4 refereed to hardware revision. No matter it works nice with RouterStats (thanks to those who have written both RouterStats and DSLstats).

Eric, when it happens I end up with a new IP address and on at least one occasion I'm convinced the router LED's didn't indicate it was re syncing. The router doesn't come back at the same speed but near, within about +/-200Kbs.

Does this suggest something to you?

FYI, the ISP is coming out; again!

[roseway]

So the connection drops when you receive an incoming telephone call. If that still happens with the router plugged into the test socket, it's a fairly certain indicator that there's a line fault of some kind. Often but not always you will hear some crackling or hissing on the telephone, which would confirm a line fault.

Hopefully the next engineer to turn up will know what he/she is doing.