Upgrade to ADSL2+ - How quickly should DLM adapt?

[Kit]

Hi,

Early this morning I was switched from ADSL to ADSL2+ (different ISPs).
There was no problem resetting my router and since 9 am it has been
rock solid with these stats:

ADSL Status
Mode ADSL2+(G.992.5)
State SHOWTIME
Up Speed 1152000
Down Speed 18325000
SNR Margin 6
Loop Att. 27

Shortly before noon I did a BT speed test and got this:

Download speed achieved during the test was - 7298 Kbps
For your connection, the acceptable range of speeds is 1000-7150 Kbps.
Additional Information:
Your DSL Connection Rate :18324 Kbps(DOWN-STREAM), 1152 Kbps(UP-STREAM)
IP Profile for your line is - 7150 Kbps
The throughput of Best Efforts (BE) classes achieved during the test is
- 14.94:21.81:63.25 (SBE:NBE:PBE)

I presume the DLM takes time to adapt so round 5.30 pm I did another BT
speed test and got this:

Download speed achieved during the test was - 7341 Kbps
For your connection, the acceptable range of speeds is 1000-7150 Kbps.
Additional Information:
Your DSL Connection Rate :18324 Kbps(DOWN-STREAM), 1152 Kbps(UP-STREAM)
IP Profile for your line is - 7150 Kbps
The throughput of Best Efforts (BE) classes achieved during the
test is - 14.43:23.34:62.24 (SBE:NBE:PBE)

i.e. no difference in the profile.

Should there not have been at least a little increase in the profile by
now?

How quickly does the DLM usually adapt?

Thanks,

Kit

[David]

I use this speed and ping tester.

http://www.speedtest.net/

Regards
David

[djp]

Post by Kit
Hi,
Early this morning I was switched from ADSL to ADSL2+ (different ISPs).
There was no problem resetting my router and since 9 am it has been rock
ADSL Status Mode ADSL2+(G.992.5) State SHOWTIME Up Speed 1152000 Down
Speed 18325000 SNR Margin 6 Loop Att. 27
Download speed achieved during the test was - 7298 Kbps
For your connection, the acceptable range of speeds is 1000-7150 Kbps.
Your DSL Connection Rate :18324 Kbps(DOWN-STREAM), 1152 Kbps(UP-STREAM)
IP Profile for your line is - 7150 Kbps
The throughput of Best Efforts (BE) classes achieved during the test is -
14.94:21.81:63.25 (SBE:NBE:PBE)
I presume the DLM takes time to adapt so round 5.30 pm I did another BT
Download speed achieved during the test was - 7341 Kbps
For your connection, the acceptable range of speeds is 1000-7150 Kbps.
Your DSL Connection Rate :18324 Kbps(DOWN-STREAM), 1152 Kbps(UP-STREAM)
IP Profile for your line is - 7150 Kbps
The throughput of Best Efforts (BE) classes achieved during the test is -
14.43:23.34:62.24 (SBE:NBE:PBE)
i.e. no difference in the profile.
Should there not have been at least a little increase in the profile by
now?
How quickly does the DLM usually adapt?

ADSL2+ has a ten day training period, to establish line stability. I
recently moved from ADSL to ADSL2+ and when ADSL2+ first turned up the
profile was set to 21000, the maximum, and took about three days set a real
value. Don't touch the router at all during the training period, there is a
risk on the DLM seeing disconnections as a bad line for which it will reduce
the speeds.

Anyway you are doing better than I did, I had very stable ADSL synced at
7616kb/s with a profile of 6500kb/s, now I have ADSL2+ synced at 4543kb/s
with a profile of 3500kb/s.

[Brian Gregory [UK]]

Post by djp

Post by Kit
Hi,
Early this morning I was switched from ADSL to ADSL2+ (different ISPs).
There was no problem resetting my router and since 9 am it has been rock
ADSL Status Mode ADSL2+(G.992.5) State SHOWTIME Up Speed 1152000 Down
Speed 18325000 SNR Margin 6 Loop Att. 27
Download speed achieved during the test was - 7298 Kbps
For your connection, the acceptable range of speeds is 1000-7150 Kbps.
Your DSL Connection Rate :18324 Kbps(DOWN-STREAM), 1152 Kbps(UP-STREAM)
IP Profile for your line is - 7150 Kbps
The throughput of Best Efforts (BE) classes achieved during the test is -
14.94:21.81:63.25 (SBE:NBE:PBE)
I presume the DLM takes time to adapt so round 5.30 pm I did another BT
Download speed achieved during the test was - 7341 Kbps
For your connection, the acceptable range of speeds is 1000-7150 Kbps.
Your DSL Connection Rate :18324 Kbps(DOWN-STREAM), 1152 Kbps(UP-STREAM)
IP Profile for your line is - 7150 Kbps
The throughput of Best Efforts (BE) classes achieved during the test is -
14.43:23.34:62.24 (SBE:NBE:PBE)
i.e. no difference in the profile.
Should there not have been at least a little increase in the profile by
now?
How quickly does the DLM usually adapt?

ADSL2+ has a ten day training period, to establish line stability. I

It's important to say that this is a characteristic of BT's way of doing it,
not of ADSL2+.

If yout ISP has it's own equpment at the exchage (LLU) it will be different.

Post by djp
recently moved from ADSL to ADSL2+ and when ADSL2+ first turned up the
profile was set to 21000, the maximum, and took about three days set a real
value. Don't touch the router at all during the training period, there is a
risk on the DLM seeing disconnections as a bad line for which it will reduce
the speeds.
Anyway you are doing better than I did, I had very stable ADSL synced at
7616kb/s with a profile of 6500kb/s, now I have ADSL2+ synced at 4543kb/s
with a profile of 3500kb/s.

[Andy Furniss]

Post by djp
Anyway you are doing better than I did, I had very stable ADSL synced at
7616kb/s with a profile of 6500kb/s, now I have ADSL2+ synced at 4543kb/s
with a profile of 3500kb/s.

Some routers have settings so you can tell it not to use ADSL2. I
haven't got a clue if it will gain you anything, though.

[David Pitt]

Post by djp
Anyway you are doing better than I did, I had very stable ADSL synced at
7616kb/s with a profile of 6500kb/s, now I have ADSL2+ synced at
4543kb/s with a profile of 3500kb/s.

Some routers have settings so you can tell it not to use ADSL2. I haven't
got a clue if it will gain you anything, though.

It is beginning to look like the problem may be router, Netgear DG834v3,
related resulting in spurious disconnections that had an adverse effect on
the ADSL2+ training. Of course all this went unseen for some days until I
got disconnected while online to my bank.

A Voyager 2110 is now in use and, so far and fingers crossed, has been
completely stable. The sync rate has risen a bit to 6655kb/s, but I suspect
the original ASDL2+ training got somewhat stuffed. My ISP is on the case,
more fingers crossed.

[Kit]

Post by Kit
ADSL Status
Mode ADSL2+(G.992.5)
State SHOWTIME
Up Speed 1152000
Down Speed 18325000
SNR Margin 6
Loop Att. 27
Download speed achieved during the test was - 7298 Kbps
For your connection, the acceptable range of speeds is 1000-7150 Kbps.
Your DSL Connection Rate :18324 Kbps(DOWN-STREAM), 1152 Kbps(UP-STREAM)
IP Profile for your line is - 7150 Kbps

When I tested this morning there had been some change.

IP profile is now 16000 Kbps but SNR has zoomed up from 6 to 27 and DSL
connection rate dropped to 6852 Kbps. Loop Att is now 29.

Presumably that at least means that the DLM has started to adapt?

Kit

[WCZ]

Post by Kit
IP profile is now 16000 Kbps but SNR has zoomed up from 6 to 27 and DSL
connection rate dropped to 6852 Kbps. Loop Att is now 29.
Presumably that at least means that the DLM has started to adapt?

I think that means 'something' happened which caused your SNR margin to
plummet meaning your router had to resync and you're now where you are. You
should get you router to resync with the exchange but its probably already
too late for your high profile. You'll need to wait for that to go back up
again once you're back at the higher sync speed which should *only* take a
few hours if BT are to believed as its a huge change.

[Rodney Pont]

Post by Kit
IP profile is now 16000 Kbps but SNR has zoomed up from 6 to 27 and DSL
connection rate dropped to 6852 Kbps. Loop Att is now 29.

The two ends auto negotiate drops in sync rate due to noise but I don't
think they auto negotiate increases. If it was me I'd disconnect and
then reconnect and see if it goes up again. If it keeps dropping I'd be
thinking of regular monitoring to try and see when it drops.

[Rodney Pont]

Post by Rodney Pont

Post by Kit
IP profile is now 16000 Kbps but SNR has zoomed up from 6 to 27 and DSL
connection rate dropped to 6852 Kbps. Loop Att is now 29.

The two ends auto negotiate drops in sync rate due to noise but I don't
think they auto negotiate increases. If it was me I'd disconnect and
then reconnect and see if it goes up again. If it keeps dropping I'd be
thinking of regular monitoring to try and see when it drops.

This explains what happens:
http://www.thinkbroadband.com/files/broadband-max-myths-and-legends.pdf

[Kit]

Post by Rodney Pont

Post by Rodney Pont

Post by Kit
IP profile is now 16000 Kbps but SNR has zoomed up from 6 to 27 and DSL
connection rate dropped to 6852 Kbps. Loop Att is now 29.

The two ends auto negotiate drops in sync rate due to noise but I don't
think they auto negotiate increases. If it was me I'd disconnect and
then reconnect and see if it goes up again. If it keeps dropping I'd be
thinking of regular monitoring to try and see when it drops.

http://www.thinkbroadband.com/files/broadband-max-myths-and-legends.pdf

Thanks for this.

The IP profile has now dropped from 16000 Kbps to 5500 Kbps and SNR is
still high (27).

Am I correct in thinking the drop in connection rate from about 18000
Kbps yesterday to about 6600 Kbps today is caused by the huge increase
in SNR from 6 to 27? Is there anything I can do about that?

I looked at the above linked document and to be honest I'm still
confused by all the alphabet soup of initials. For example, I thought
one shouldn't turn off or disconnect the modem/router during the
training period, but in the document it says:
QUOTE
Does my modem automatically retrain to a higher line rate?
No, currently the end user will have to force a retrain by turning the
modem off and back on, or via the GUI to retrain to a higher speed.
UNQUOTE

So doesn't that mean that if I'm now on this low line rate with high
SNR then I'll have to switch off the modem in order to get it to go
back to its initial high rate and low SNR?

Kit

[WCZ]

Post by Kit
Am I correct in thinking the drop in connection rate from about 18000
Kbps yesterday to about 6600 Kbps today is caused by the huge increase
in SNR from 6 to 27? Is there anything I can do about that?

Yes and reboot the router to fix it.

Post by Kit
So doesn't that mean that if I'm now on this low line rate with high
SNR then I'll have to switch off the modem in order to get it to go
back to its initial high rate and low SNR?

Yes.

Then you'll have to wait for the BRAS profile to update before you'll get
any higher data transfer rates.

[Graham J]

Post by Kit

Post by Rodney Pont

Post by Rodney Pont

Post by Kit
IP profile is now 16000 Kbps but SNR has zoomed up from 6 to 27 and DSL
connection rate dropped to 6852 Kbps. Loop Att is now 29.

The two ends auto negotiate drops in sync rate due to noise but I don't
think they auto negotiate increases. If it was me I'd disconnect and
then reconnect and see if it goes up again. If it keeps dropping I'd be
thinking of regular monitoring to try and see when it drops.

http://www.thinkbroadband.com/files/broadband-max-myths-and-legends.pdf

Thanks for this.
The IP profile has now dropped from 16000 Kbps to 5500 Kbps and SNR is
still high (27).
Am I correct in thinking the drop in connection rate from about 18000
Kbps yesterday to about 6600 Kbps today is caused by the huge increase
in SNR from 6 to 27? Is there anything I can do about that?

The change in SNR margin is a response, not a cause. There was some noise
event, and the SNR margin was increased in response. Consequently the data
rate reduced. These two actions together ensure that the connection remains
stable.

If you reboot the router the new connection may negotiate a lower SNR margin
and a higher data rate. But the figures will change for the poorer next
time there is a noise event.

The resolution is to remove the cause of the noise event.

Remove all possible cause of problems with your house wiring by fitting a
faceplate filter on the master socket, and following all other good
practises, as described elsewhere in the NG.

Listen for noise on the line using the BT "quiet line" test, and get any
noise corrected by your telephony provider.

After that, keep logs of all changes in SNR margin & data rate.. Check the
FTR for your line (a good ISP will offer a website where you can find this
figure). If the line rate drops below the FTR your ISP will be able to get
BT to resolve the issue. Whether your ISP is prepared to do so is quite
another matter; but if not, change to a professional ISP.

[Rodney Pont]

Post by Graham J
The change in SNR margin is a response, not a cause. There was some noise
event, and the SNR margin was increased in response. Consequently the data
rate reduced. These two actions together ensure that the connection remains
stable.

It also possible that the noise caused the SNR margin to fall so it
retrained slower to get the SNR margin back up again. Then the noise
cleared up so the SNR margin rose. You have to resync to raise the
speed and get a lower SNR margin.

[Kit]

Post by Rodney Pont

Post by Graham J
The change in SNR margin is a response, not a cause. There was some noise
event, and the SNR margin was increased in response. Consequently the data
rate reduced. These two actions together ensure that the connection remains
stable.

It also possible that the noise caused the SNR margin to fall so it
retrained slower to get the SNR margin back up again. Then the noise
cleared up so the SNR margin rose. You have to resync to raise the
speed and get a lower SNR margin.

Apparently either my couple of attempts to resynch or some glitch
(noise or power cut) caused the BT equipment to determine my line was
unstable, even though it's been perfectly stable on ADSL for over a
year.

Anyway, if I interpret my router stats correctly, I've been put onto a
'banded profile'. IDNet tell me:
"once the line is stable for between 48 and 72 hours the banded
profile may be automatically removed"

MAY be automatically removed? Don't they mean it WILL be automatically
removed?

Kit

[The Natural Philosopher]

Post by Kit

Post by Rodney Pont

Post by Graham J
The change in SNR margin is a response, not a cause. There was some noise
event, and the SNR margin was increased in response. Consequently the data
rate reduced. These two actions together ensure that the connection remains
stable.

It also possible that the noise caused the SNR margin to fall so it
retrained slower to get the SNR margin back up again. Then the noise
cleared up so the SNR margin rose. You have to resync to raise the
speed and get a lower SNR margin.

Apparently either my couple of attempts to resynch or some glitch
(noise or power cut) caused the BT equipment to determine my line was
unstable, even though it's been perfectly stable on ADSL for over a
year.
Anyway, if I interpret my router stats correctly, I've been put onto a
"once the line is stable for between 48 and 72 hours the banded
profile may be automatically removed"
MAY be automatically removed? Don't they mean it WILL be automatically
removed?

IDNET are good people. phone up and explain, without getting emotional.

They will get BT to reset it to something sane@: After that, you are on
your own.

Post by Kit
Kit

[Comtroll]

Post by The Natural Philosopher

Post by Kit

Post by Rodney Pont

Post by Graham J
The change in SNR margin is a response, not a cause. There was some
noise event, and the SNR margin was increased in response.
Consequently the data rate reduced. These two actions together
ensure that the connection remains stable.

It also possible that the noise caused the SNR margin to fall so it
retrained slower to get the SNR margin back up again. Then the noise
cleared up so the SNR margin rose. You have to resync to raise the
speed and get a lower SNR margin.

Apparently either my couple of attempts to resynch or some glitch
(noise or power cut) caused the BT equipment to determine my line was
unstable, even though it's been perfectly stable on ADSL for over a
year.
Anyway, if I interpret my router stats correctly, I've been put onto a
"once the line is stable for between 48 and 72 hours the banded
profile may be automatically removed"
MAY be automatically removed? Don't they mean it WILL be automatically
removed?

IDNET are good people. phone up and explain, without getting emotional.

Bollocks. They are shit hopeless. Don't bother calling them until Monday
- you'll find there is no fucker there. Absolutely shit ISP used by
morons.

[Kit]

Post by Graham J
The change in SNR margin is a response, not a cause. There was some noise
event, and the SNR margin was increased in response. Consequently the data
rate reduced. These two actions together ensure that the connection remains
stable.

Thanks for this. I guess that to go overnight from SNR of 6 to SNR of
27 the 'noise event' must have been pretty drastic!

Post by Graham J
If you reboot the router the new connection may negotiate a lower SNR margin
and a higher data rate. But the figures will change for the poorer next
time there is a noise event.
The resolution is to remove the cause of the noise event.

Perhaps I should say that For over a year I had very stable ADSL with
SNR between 6 and 9, Attenuation around 25, connection rate around 8000
Kbps and IP profile of about 7150 Kbps. Yesterday I migrated to
ADSL2+.

I'm using the same modem/router now (in ADSL2+ mode) and nothing else
on my side of the socket has changed. The initial connection rate was
18325 Kbps with SNR 6 and Att 27, but the IP profile remained at 7150
Kbps and those stats remained pretty constant up until I went to bed
last night.

Early his morning the connection rate was 6652 Kbs with SNR 27, Att 30
and IP profile of 16000 Kbps.

Now the connection rate is still 6652 Kbps with SNR 26, Att 27 and IP
profile now down to 5500 Kbps.

Post by Graham J
Remove all possible cause of problems with your house wiring by fitting a
faceplate filter on the master socket, and following all other good
practises, as described elsewhere in the NG.

The ADSL comes in to a master socket fitted by BT. The only connections
to that socket are the modem/router and one phone (no extensions). All
is exactly the same as it has been for the past year when SNR were
always between 6 and 9. There is no new equipment in my house

Post by Graham J
Listen for noise on the line using the BT "quiet line" test, and get any
noise corrected by your telephony provider.

Just tried that and the line sounds very quiet to me.

FWIW the migration was from entanet ADSL to IDNet ADSL2+. I'm not sure
if you consider either of those to be professional! :-)

Thanks again for your input.

Kit

[Graham J]

Post by Kit

Post by Graham J
The change in SNR margin is a response, not a cause. There was some noise
event, and the SNR margin was increased in response. Consequently the data
rate reduced. These two actions together ensure that the connection remains
stable.

Thanks for this. I guess that to go overnight from SNR of 6 to SNR of
27 the 'noise event' must have been pretty drastic!

Post by Graham J
If you reboot the router the new connection may negotiate a lower SNR margin
and a higher data rate. But the figures will change for the poorer next
time there is a noise event.
The resolution is to remove the cause of the noise event.

Perhaps I should say that For over a year I had very stable ADSL with
SNR between 6 and 9, Attenuation around 25, connection rate around 8000
Kbps and IP profile of about 7150 Kbps. Yesterday I migrated to
ADSL2+.
I'm using the same modem/router now (in ADSL2+ mode) and nothing else
on my side of the socket has changed. The initial connection rate was
18325 Kbps with SNR 6 and Att 27, but the IP profile remained at 7150
Kbps and those stats remained pretty constant up until I went to bed
last night.
Early his morning the connection rate was 6652 Kbs with SNR 27, Att 30
and IP profile of 16000 Kbps.
Now the connection rate is still 6652 Kbps with SNR 26, Att 27 and IP
profile now down to 5500 Kbps.

Post by Graham J
Remove all possible cause of problems with your house wiring by fitting a
faceplate filter on the master socket, and following all other good
practises, as described elsewhere in the NG.

The ADSL comes in to a master socket fitted by BT. The only connections
to that socket are the modem/router and one phone (no extensions). All
is exactly the same as it has been for the past year when SNR were
always between 6 and 9. There is no new equipment in my house

Post by Graham J
Listen for noise on the line using the BT "quiet line" test, and get any
noise corrected by your telephony provider.

Just tried that and the line sounds very quiet to me.
FWIW the migration was from entanet ADSL to IDNet ADSL2+. I'm not sure
if you consider either of those to be professional! :-)

So you're in the sorry position that by opting for an improved service (from
ADSL to ADSL2+) you have suffered a reduced profile from 7150 kbits/sec to
5500 kbits/sec.

There is always the possibility that you experienced an exceptional noise
event. If so, probably the profile will improve over the coming weeks. It
may help to reboot the router every week or so.

The ADSL2+ technology requires a greater available bandwidth, and it may be
that there is noise in the part of the spectrum that wasn't used by the
older ADSL system. But it surprises me that such circumstances would reduce
the speed below what you had previously.

Perhaps you should talk to your ISP. If ADSL2+ gives poorer performance
maybe you should revert to ADSL.

As to whether your chosen ISP is professional - I will leave others to
comment. Try talking to them - that will give you an idea ...

[Kit]

Post by Graham J
The ADSL2+ technology requires a greater available bandwidth, and it may be
that there is noise in the part of the spectrum that wasn't used by the
older ADSL system. But it surprises me that such circumstances would reduce
the speed below what you had previously.

From 9 am (immediately after ADSL2+ activation) until after 9 pm
yesterday the connection was solid with connection rate 18324 Kbps and
SNR 6. Would SNR not have jumped up sooner if the cause was the noise
was in the higher ADSL2+ spectrum?

Thanks again,

Kit

[Graham J]

Post by Kit

Post by Graham J
The ADSL2+ technology requires a greater available bandwidth, and it may be
that there is noise in the part of the spectrum that wasn't used by the
older ADSL system. But it surprises me that such circumstances would reduce
the speed below what you had previously.

From 9 am (immediately after ADSL2+ activation) until after 9 pm
yesterday the connection was solid with connection rate 18324 Kbps and
SNR 6. Would SNR not have jumped up sooner if the cause was the noise
was in the higher ADSL2+ spectrum?

The point about noise is that it may be there only intermittently ....!!

[WCZ]

Post by Kit
Early his morning the connection rate was 6652 Kbs with SNR 27, Att 30
and IP profile of 16000 Kbps.
Now the connection rate is still 6652 Kbps with SNR 26, Att 27 and IP
profile now down to 5500 Kbps.

That sync rate rings a bell with me. During the early days of BTs ADSL2+
migration I seem to remember a number of people with lines that wouldn't
sync above 6652 regardless of how big the noise margin was. I'm sure BT
denied any and all problems but it was something to do with their kit in the
exchange. If a router reboot doesn't increase your sync you may have to
talk to IDNET about it.

[Kit]

Post by WCZ

Post by Kit
Early his morning the connection rate was 6652 Kbs with SNR 27, Att 30
and IP profile of 16000 Kbps.
Now the connection rate is still 6652 Kbps with SNR 26, Att 27 and IP
profile now down to 5500 Kbps.

That sync rate rings a bell with me. During the early days of BTs ADSL2+
migration I seem to remember a number of people with lines that wouldn't
sync above 6652 regardless of how big the noise margin was. I'm sure BT
denied any and all problems but it was something to do with their kit in the
exchange. If a router reboot doesn't increase your sync you may have to
talk to IDNET about it.

I did one reboot on the night of 9th Sept when my router had had over
12 hours of a connection rate of over 18000 Kbps and SNR of 6 but IP
profile of only 7150. Maybe that reboot was a stupid thing to do.

The next morning (10th Sept), after I saw the connection rate had
dropped to 6652 and SNR was 27, though profile was 16000 I tried
another reboot. After that the rate and SNR were the same but IP
profile dropped to 5550.

For the whole of yesterday the rate remained at 6652, SNR at 25-27 and
IP profile at 5550.

When I reported that to IDNet I was told that either I had a noisy line
or that it was because I'd rebooted the router during training. They
told me that I shouldn't reboot again or I'd make things worse.

I'm very close to the exchange and always get Loop Att between 27 and
30. For well over a year I had rock-solid connections with ADSL and got
downloads as fast as ADSL can go with SNR 6-9. I really can't believe
that my line quality has gone from great to terrible just
coincidentally with the changeover from ADSL to ADSL2+

Maybe some glitch of noise or overnight power failure cause my router
to disconnect overnight on 9th-10th Sept and that persuaded the BT
equipment that I have an unstable connection.

Presuming that I don't reboot the router again, that the line quality
is still actually good, and that the problem was a glitch, how soon
would the equipment in the exchange start bringing the SNR down again?

Kit

[The Natural Philosopher]

Post by Kit

Post by WCZ

Post by Kit
Early his morning the connection rate was 6652 Kbs with SNR 27, Att 30
and IP profile of 16000 Kbps.
Now the connection rate is still 6652 Kbps with SNR 26, Att 27 and IP
profile now down to 5500 Kbps.

That sync rate rings a bell with me. During the early days of BTs ADSL2+
migration I seem to remember a number of people with lines that wouldn't
sync above 6652 regardless of how big the noise margin was. I'm sure BT
denied any and all problems but it was something to do with their kit in the
exchange. If a router reboot doesn't increase your sync you may have to
talk to IDNET about it.

I did one reboot on the night of 9th Sept when my router had had over
12 hours of a connection rate of over 18000 Kbps and SNR of 6 but IP
profile of only 7150. Maybe that reboot was a stupid thing to do.
The next morning (10th Sept), after I saw the connection rate had
dropped to 6652 and SNR was 27, though profile was 16000 I tried
another reboot. After that the rate and SNR were the same but IP
profile dropped to 5550.
For the whole of yesterday the rate remained at 6652, SNR at 25-27 and
IP profile at 5550.
When I reported that to IDNet I was told that either I had a noisy line
or that it was because I'd rebooted the router during training. They
told me that I shouldn't reboot again or I'd make things worse.
I'm very close to the exchange and always get Loop Att between 27 and
30. For well over a year I had rock-solid connections with ADSL and got
downloads as fast as ADSL can go with SNR 6-9. I really can't believe
that my line quality has gone from great to terrible just
coincidentally with the changeover from ADSL to ADSL2+
Maybe some glitch of noise or overnight power failure cause my router
to disconnect overnight on 9th-10th Sept and that persuaded the BT
equipment that I have an unstable connection.
Presuming that I don't reboot the router again, that the line quality
is still actually good, and that the problem was a glitch, how soon
would the equipment in the exchange start bringing the SNR down again?

IME several weeks or a month.

IDnet can and will request an SNR change, but it may not stick. I tried
it, it worked for a few days, then back to what it was.

Last night, BT decided that, for no apparent reason, I should go back to
a 9dB noise margin. It does this and then about 6 weeks after the line
has been rock solid, they decide a 6dB margin is OK, that also lasts for
6 weeks, then they decide I should be on 9dB again.

The graphs of this clearly show the steps every 6 weeks, as they change it.

It doesn't actually make a deal of difference to me, since although I
connect at about 3700 when on 9dB and 4000+ or so on 6dB my BRAS has,
but for a nice clear period of low noise in summer, stuck resolutely at
3000.

Fortunately, IDnet being a low contention ISP, Or perhaps because the
exchange backhaul is not highly contended, I get that sort of download
rate as well.

I suspect from this that the BT algorithm is somewhat like this

IF(syncrate < BRAS+1000)
set BRAS to less than (syncrate -500)
IF(less than (some small number) of resynchs in 6 weeks)
then try lowerSNR margin.
IF(more than (some small number of resynchs) in 6 weeks)
then try some higher SNR number.
IF(syncrate < BRAS + 1000 for 6 weeks)
then try higher BRAS.
It is not clear whether the 6 weeks it total up time or total online time.

Post by Kit
Kit

[Comtroll]

Post by The Natural Philosopher
I suspect from this that the BT algorithm is somewhat like this
IF(syncrate < BRAS+1000)
set BRAS to less than (syncrate -500)
IF(less than (some small number) of resynchs in 6 weeks)
then try lowerSNR margin.
IF(more than (some small number of resynchs) in 6 weeks)
then try some higher SNR number.
IF(syncrate < BRAS + 1000 for 6 weeks)
then try higher BRAS.
It is not clear whether the 6 weeks it total up time or total online time.

Rubbish Michael,

It's like this:
IDNET PAY FOR X - IDNET GET X (NOT X+A BIT MORE)
Gets busy - congested - BT CAP IDNET CUSTOMERS as part of IDNET's
'STEALTH' TRAFFIC MANAGEMENT POLICY.

Simples. Compare the crap ISP dot com......

[Kit]

Post by The Natural Philosopher
Last night, BT decided that, for no apparent reason, I should go back to
a 9dB noise margin. It does this and then about 6 weeks after the line
has been rock solid, they decide a 6dB margin is OK, that also lasts for
6 weeks, then they decide I should be on 9dB again.

Well, SNR going from 6dB to 9dB is one thing, and I probably wouldn't
really notice that, but going overnight from 6dB to 27dB is a huge
difference, especially as it is (IIUC) a logarithmic scale.

I was rather hoping that such a big overnight stepwise increase might
be undone a little more quickly than 3dB every 6 weeks! At that rate it
would take about 10 months to get back to 'normal'. :(

Kit

[The Natural Philosopher]

Post by Kit

Post by The Natural Philosopher
Last night, BT decided that, for no apparent reason, I should go back to
a 9dB noise margin. It does this and then about 6 weeks after the line
has been rock solid, they decide a 6dB margin is OK, that also lasts for
6 weeks, then they decide I should be on 9dB again.

Well, SNR going from 6dB to 9dB is one thing, and I probably wouldn't
really notice that, but going overnight from 6dB to 27dB is a huge
difference, especially as it is (IIUC) a logarithmic scale.
I was rather hoping that such a big overnight stepwise increase might
be undone a little more quickly than 3dB every 6 weeks! At that rate it
would take about 10 months to get back to 'normal'. :(

I think that if the line is now stable, you should get it reset manually.

Post by Kit
Kit

[WCZ]

Post by The Natural Philosopher

Post by Kit
I was rather hoping that such a big overnight stepwise increase might
be undone a little more quickly than 3dB every 6 weeks! At that rate it
would take about 10 months to get back to 'normal'. :(

I think that if the line is now stable, you should get it reset manually.

Post by Kit
Kit

Yes, you will have to do it manually. Your SNR margin, and hence your sync
speed, will never change unless you reboot the router. The high margin you
currently have is due to a burst of noise that caused your router to lose
connection with the exchange. The connection was re-established
automatically but at a lower speed. Now that noise appears to have gone and
you have your 27dB margin. The only way that will change to
6/9/12./whatever BT deem suitable will be if you do a router reboot.

Of course your problem then might be that you get another burst of noise in
the middle of the night that sparks off the above process again.

[Mark]

Post by Kit

Post by The Natural Philosopher
Last night, BT decided that, for no apparent reason, I should go back to
a 9dB noise margin. It does this and then about 6 weeks after the line
has been rock solid, they decide a 6dB margin is OK, that also lasts for
6 weeks, then they decide I should be on 9dB again.

Well, SNR going from 6dB to 9dB is one thing, and I probably wouldn't
really notice that, but going overnight from 6dB to 27dB is a huge
difference, especially as it is (IIUC) a logarithmic scale.

There's a difference between the target SNR margin and the actual SNR
margin. Your actual margin has increased massively probably to a
burst of noise that forced a resync. A manual resync of your router
will sort this problem out.

Post by Kit
I was rather hoping that such a big overnight stepwise increase might
be undone a little more quickly than 3dB every 6 weeks! At that rate it
would take about 10 months to get back to 'normal'. :(

I can confirm that a downwards change to target margin can take a lot
longer than 6 weeks. Upwards changes happen a lot more frequently.

Last year I had my SNR reset several times after a fault was "fixed".
After as little as two days with no problems it was back to 12dB.
Months later it had not gone down. I'm not sure when it dropped but
now it is back to 9dB.

[Mark]

Post by Graham J

Post by Kit

Post by Rodney Pont

Post by Rodney Pont

Post by Kit
IP profile is now 16000 Kbps but SNR has zoomed up from 6 to 27 and DSL
connection rate dropped to 6852 Kbps. Loop Att is now 29.

The two ends auto negotiate drops in sync rate due to noise but I don't
think they auto negotiate increases. If it was me I'd disconnect and
then reconnect and see if it goes up again. If it keeps dropping I'd be
thinking of regular monitoring to try and see when it drops.

http://www.thinkbroadband.com/files/broadband-max-myths-and-legends.pdf

Thanks for this.
The IP profile has now dropped from 16000 Kbps to 5500 Kbps and SNR is
still high (27).
Am I correct in thinking the drop in connection rate from about 18000
Kbps yesterday to about 6600 Kbps today is caused by the huge increase
in SNR from 6 to 27? Is there anything I can do about that?

The change in SNR margin is a response, not a cause. There was some noise
event, and the SNR margin was increased in response. Consequently the data
rate reduced. These two actions together ensure that the connection remains
stable.
If you reboot the router the new connection may negotiate a lower SNR margin
and a higher data rate. But the figures will change for the poorer next
time there is a noise event.
The resolution is to remove the cause of the noise event.
Remove all possible cause of problems with your house wiring by fitting a
faceplate filter on the master socket, and following all other good
practises, as described elsewhere in the NG.
Listen for noise on the line using the BT "quiet line" test, and get any
noise corrected by your telephony provider.
After that, keep logs of all changes in SNR margin & data rate.. Check the
FTR for your line (a good ISP will offer a website where you can find this
figure). If the line rate drops below the FTR your ISP will be able to get
BT to resolve the issue. Whether your ISP is prepared to do so is quite
another matter; but if not, change to a professional ISP.

Since this has happened during the stablisation period then the OP's
MSR/FTR will be very low anyway. (BTw do also recalculate MSR and FTR
at other times so dealing with speed issues can be tricky.)

[Brian Gregory [UK]]

Post by Graham J

Post by Kit

Post by Rodney Pont

Post by Rodney Pont

Post by Kit
IP profile is now 16000 Kbps but SNR has zoomed up from 6 to 27 and DSL
connection rate dropped to 6852 Kbps. Loop Att is now 29.

The two ends auto negotiate drops in sync rate due to noise but I don't
think they auto negotiate increases. If it was me I'd disconnect and
then reconnect and see if it goes up again. If it keeps dropping I'd be
thinking of regular monitoring to try and see when it drops.

http://www.thinkbroadband.com/files/broadband-max-myths-and-legends.pdf

Thanks for this.
The IP profile has now dropped from 16000 Kbps to 5500 Kbps and SNR is
still high (27).
Am I correct in thinking the drop in connection rate from about 18000
Kbps yesterday to about 6600 Kbps today is caused by the huge increase
in SNR from 6 to 27? Is there anything I can do about that?

The change in SNR margin is a response, not a cause. There was some noise
event, and the SNR margin was increased in response. Consequently the
data rate reduced. These two actions together ensure that the connection
remains stable.
If you reboot the router the new connection may negotiate a lower SNR
margin and a higher data rate. But the figures will change for the poorer
next time there is a noise event.

ADSL2+ includes a feature (which your modem and your ISP may or may not
implement) whereby the connection speed can adjust to match slowly changing
noise conditions without re-syncing.

So with ADSL2+ done properly I would expect to see sync speeds higher during
the day and lower at night even if the connection never has to re-sync.

Post by Graham J
The resolution is to remove the cause of the noise event.
Remove all possible cause of problems with your house wiring by fitting a
faceplate filter on the master socket, and following all other good
practises, as described elsewhere in the NG.
Listen for noise on the line using the BT "quiet line" test, and get any
noise corrected by your telephony provider.
After that, keep logs of all changes in SNR margin & data rate.. Check
the FTR for your line (a good ISP will offer a website where you can find
this figure). If the line rate drops below the FTR your ISP will be able
to get BT to resolve the issue. Whether your ISP is prepared to do so is
quite another matter; but if not, change to a professional ISP.

[alexd]

Meanwhile, at the uk.telecom.broadband Job Justification Hearings, Brian

Post by Brian Gregory [UK]
ADSL2+ includes a feature (which your modem and your ISP may or may not
implement) whereby the connection speed can adjust to match slowly
changing noise conditions without re-syncing.
So with ADSL2+ done properly I would expect to see sync speeds higher
during the day and lower at night even if the connection never has to
re-sync.

SRA being the relevant TLA IIRC, in case anybody wants to JFGI

[Eeyore]

Post by Kit
Hi,
Early this morning I was switched from ADSL to ADSL2+ (different ISPs).
There was no problem resetting my router and since 9 am it has been
ADSL Status
Mode ADSL2+(G.992.5)
State SHOWTIME
Up Speed 1152000
Down Speed 18325000
SNR Margin 6
Loop Att. 27
Download speed achieved during the test was - 7298 Kbps
For your connection, the acceptable range of speeds is 1000-7150 Kbps.
Your DSL Connection Rate :18324 Kbps(DOWN-STREAM), 1152 Kbps(UP-STREAM)
IP Profile for your line is - 7150 Kbps
The throughput of Best Efforts (BE) classes achieved during the test is
- 14.94:21.81:63.25 (SBE:NBE:PBE)
I presume the DLM takes time to adapt so round 5.30 pm I did another BT
Download speed achieved during the test was - 7341 Kbps
For your connection, the acceptable range of speeds is 1000-7150 Kbps.
Your DSL Connection Rate :18324 Kbps(DOWN-STREAM), 1152 Kbps(UP-STREAM)
IP Profile for your line is - 7150 Kbps
The throughput of Best Efforts (BE) classes achieved during the
test is - 14.43:23.34:62.24 (SBE:NBE:PBE)
i.e. no difference in the profile.
Should there not have been at least a little increase in the profile by
now?

I suspect the BT speedtester is mis-reporting.

Graham