It was supposition based on limited information. Turns out that the line may well be quite stable and it is the high target SNR that is stopping any faster syncs (although could still have some instability).

I have seen a 2Mb swing between day and night on my parents line. They can happily hold a 6Mb sync during the day but once night hits it resyncs regularly until it drops to about 4Mb. This I believe is primarily to do with it being overhead lines and not helped by the fact it passes by a number of trees that have overhanging branches.

Now that we have the stats from the sync immediately after a reset it is clear that the SNR is very high - it would still likely be bettered supported on LLU though as most LLU doesn't have the automated systems that kick in when the router resyncs.

You need to get your ISP to reset the target SNR. If they are any good they should be able to do that, but it may take a while to find someone in the call centre that is bright enough to sort it out. If you get it reset to 6dB (it is currently 15dB) then your sync will go up considerably.

It is possible that the high target SNR is due to previous problems on the line that have been fixed and no-one ever reset it.

However, it may make the line unstable if there are still any issues on it. If it is unstable then the BT automated systems should increase the target SNR until it is stable again (it does this in 3dB increments).

Yep ian . The OP seems not to have read where I said the same.

In reply to a post by RobertoS:

Yep ian . The OP seems not to have read where I said the same.

Indeed Hopefully they will give it a try soon.

You are confused about what the noise margin is. Note the word "margin" .

It is a figure set by the system at the moment you connect, to allow for variation in the actual background noise over 24 hours.

The background noise goes up at night so the margin falls. In the daytime the background is lower so the margin rises. Until you do a reconnect when it is set back to the system figure.

That system figure - the "target" noise margin - is what needs to be reset to 6dB. The stats taken after a reconnection were to let us see what it is, and the talk about cabling was to look for possible causes of high/variable background noise.

From what you have now, it looks like the variation with connections the way they are is small.

We now need you to put the connections back in place, with the faceplate replaced, and then monitor the noise margin a couple of times in the day and at night. Do not do further reconnections after putting things back together.

Have a read of my Noise margin and High SNRM pages for a fuller explanation.

Re the master faceplate, does it have a logo saying "Openreach"?

Edited by RobertoS (Wed 27-Oct-10 09:16:54)

Thanks for the advice. I have been reading your advice (and am grateful for it) but I have very little technical knowledge re lines, noise, resyncs etc.

What is exactly is a resync? (I have found RobertoS's site useful and I have learnt a lot but,as I say, the technical side of the internet is not my forte)

Until a few days ago we had been intermittently having trouble finding and keeping our internet connection (BTHomeHub2-C5R6) and it was not unusual to lose the connection and after disconnecting the Hub and restarting sometimes only other SKY and BT networks showed up but could not be connected to; for the past week or so the connection has been stable.

I will look at the stats again about 10am (to see if the daylight hours are better). Should I restart the Hub before doing so?

Should I restart the Hub before doing so?

If you have re-assembled the whole setup, back to normal, then no. Just check the stats. (By the way, all the garbage after the upstream results, about what to do and so on, is irrelevant, so you can miss that out of future posts ).

"Resync" . When your router connects to the exchange, which as you know takes a few seconds, the process going on is called synchronisation. It is a negotiation between the modem part of your router and the modem part of the exchange equipment (DSLAM or MSAN) to decide what speed to work at so as to go as fast as possible but avoid frequent disconnections.

So a reconnection, where you disconnect then connect, involves a sync (for short). In some setups it is possible to re-sync without fully disconnecting or turning off the router. So a re-sync and a reconnection are almost the same thing. A reconnection by definition includes a (re-)sync.

Until a few days ago we had been intermittently having trouble finding and keeping our internet connection

That's why the sync-time (target) margin has been raised to 15dB, to try to stabilise the connection. What happened to cure this? I got the impression the BT engineer was 18 months ago?

sometimes only other SKY and BT networks showed up but could not be connected to

That sounds like wireless networks, rather than wired through your router?

RobertoS thanks for your latest post which crossed with mine.

The faceplate does have Openreach on it.

I've had to disconnect from the hub to put the faceplate back and reconnect everything through the faceplate. The stats now are:

WirelessTelephonyBroadbandHome NetworkApplication SharingSystemBasic Settings
InternetADSLVPNDynamic DNSADSL line status
Connection information
Line state Connected
Connection time 0 days, 0:07:44
Downstream 2,784 Kbps
Upstream 448 Kbps


ADSL settings
VPI/VCI 0/38
Type PPPoA
Modulation ITU-T G.992.1
Latency type Interleaved
Noise margin (Down/Up) 15.3 dB / 16.0 dB
Line attenuation (Down/Up) 53.0 dB / 31.5 dB
Output power (Down/Up) 17.9 dBm / 12.3 dBm
Loss of Framing (Local) 56
Loss of Signal (Local) 5
Loss of Power (Local) 0
FEC Errors (Down/Up) 29 / 0
CRC Errors (Down/Up) 1 / 2147480000
HEC Errors (Down/Up) nil / 0
Error Seconds (Local) 148

Hide Details

Sorry for the delay but for some reason I can't do the BT speedtest. I key in the phone number and nothing is happening; I'll try soon as I haven't run a successful test on it today.

I don't know what has happened to stabilise our internet connection.

For some time there were up to 3 computers in use in our house - the one I'm using at the moment seemed to find it harder to connect but all 3 were occasionally having problems. The other 2 are laptops with built-in networking, this is a desktop with a network adapter.

For the past month or so only the desktop was in use and it had system software problems (Windows 7) and one day AVG reported some corruption of the internet adapter software but the intermittent problems predated these problems. There are no known problems with the desktop and its adapter now.

For the past week or so there have been no connection problems.

In the past when the engineer called the internet was unusable because of the speed and the fact that it would disappear completely at times. The engineer blamed it on the length of the connection and, as I've said, he managed to reroute the line. BT also gave us a HomeHub to eliminate the original router as something which might have been adding to our problems.

I assume the other networks that we can see at times are wireless networks in surrounding houses - I've confirmed my next door neighbour uses SKY.

Unfortunately I didn't know about noise stats etc until a couple of days ago so I never knew how much noise was on the line and I don't know if BT increased the margin recently or not

I have now (10.34) manged to get the BT speedtest results


0 Kbps 2000 Kbps
Max Achievable Speed

Download speedachieved during the test was - 1529 Kbps
For your connection, the acceptable range of speedsis 800-2000 Kbps.
Additional Information:
Your DSL Connection Rate :2784 Kbps(DOWN-STREAM), 448 Kbps(UP-STREAM)
IP Profile for your line is - 2000 Kbps
The throughput of Best Efforts (BE) classes achieved during the test is - 13.12:23.81:63.07 (SBE:NBE:PBE)
These figures represent the ratio while sententiously passing Sub BE, Normal BE and Priority BE marked traffic.

The results of this test will vary depending on the way your ISP has decided to use these traffic classes.

2. Upstream Test: -provides background information.

Upload Speed
352 Kbps

0 Kbps 448 Kbps
Max Achievable Speed

>Upload speed achieved during the test was - 352 Kbps
Additional Information:
Upstream Rate IP profile on your line is - 448 Kbps