Phil Long:

From our testing we know that those with sub-4 Mbit/s are least likely to see an improvement in speeds.  As you get closer to 2Mbit/s and less it becomes more likely that you'll see the same or lower speeds.

This is what I was referring to. I know the line problems are fully BT's fault and not Zen's. And Zen have been great in the past but I think they've dropped the ball on this one. If I'd been told this before the upgrade, I wouldn't have gone for it but my situation now is that I've got half the speed I used to have after an upgrade that Zen knew had a possibility of lowering my speed.

Hi

what is your current attenuation ? what is your current synch speed .

The attenuation is measured between you and the exchange .your original attenuation put your line length at about 4.1 Km.

The calculated possible synch speed based on attenuation and a standard SNR margin of 6db in most cases will show an improvement . That is as long as there isn't some abnormal noise in the higher frequencies see

expected synch rate 

the synch rate improvement may be small but even at 57db there could be some gain due to improved profile .

Regards Jeff

Hi Jeff,

Before the "upgrade" my attenuation was around 56db with a SNR of 6. My sync rate was 2272 (best figure - it varied a bit but had settled at this speed for a while).

After the move to 21CN my attenuation rocketed up to 75 (same SNR ration) and my sync speed dropped to 1152. It's now up to 1728 which is still below the old speed.

I had a line fault fixed on my line last year and the technician measured the line length at around 3-3.2km so it's less than the 4.1km that the attenuation rate suggested.

Thanks for the link to that tool. It shows that before the upgrade I should have had a sync speed of 3712 - quite a way above what I had but I'm assuming the tool gives best-case figures. Still, 1100kbps out is a bit much. When I enter my current attenuation it says the line length is 5.4km and doesn't give figures for sync rates (I believe 5.4km is outside the maximum line length that ADSL requires but I'm not 100% sure on that point.)

So this leads me into thinking that the attenuation I'm getting is abnormal for my line length for my ADSL 1 connection. After the move to ADSL2, it's sky high.

I too have pretty high attenuation on my line & upgraded to Zen Active for the increased upload speed over "8000" product ~53db. I lost DL sync speed moving to ADSL2+ and upload wouldn't sync higher than ~600k (despite router reporting >1Mb possible). After help from Zen tech support (thanks guys) I tried 1 last thing before the option of calling out a BT engineer who IMO was not going to find a physical fault on the line...

 I forced the router (Draytek 2820) to ADSL1 to see what sync I could get... immediately +300K on download and upload went from ~600k to ~950k. I then tried ADSL2 and got a bit more DL & similar upload. Switch back to ADSL2+ & slow syncs again.

 If you can force your router just try ADSL2 (G.992.3) to see what happens (or ADSL1 ). You don't need to downgrade your service again as BT's kit will quite happily sync on ADSL1/2 rather than 2+.

 Now Zen tech support have opted me in for interleaving (after BT turned it off without being asked to!) I've got _stable_ ~4400k DS and ~834k US with 9db SNR... huge improvement over my ADSL2+ sync of ~3800k DS ~600l US. 

 Hope this helps.

 Chris 

Since moving to 21CN my speeds have gone from around 6500k to now around 2000k.  Fairly disappointing. I've raised it with Zen and fingers crossed they can find the problem.

Following today's 21CN migration in the Exeter area my speed has (so far) gone up. Most significantly my BRAS profile is up from adsl3000 to adsl4000, giving me about a 1 Mbps boost.
BT speed tester before and after figures as follows:

Yesterday
D/L speed:    2788 Kbps
DSL connection rate:    4256 Kbps(D/S) / 448 Kbps (U/S)
IP Profile: 3000 Kbps

Today
D/L speed:    4089 Kbps
DSL connection rate:    4864 Kbps(D/S) / 448 Kbps (U/S)
IP Profile: 4000 Kbps

Here's hoping this profile persists as I think it should always have been 4000!

I was upgraded to 21CN yesterday (12 May).

I ran a speed test using the thinkbroadband speed tester the day before and it returned a download speed of ca 6.4Mb/s which is consitent with what I've have since BT fixed my line a couple of months ago.

After the 'upgrade' to 21CN my speed initially dropped to about 1.4Mb/s both in terms of BRAS profile (1500) and in terms of download speed.

As advised in the Zen letter I got telling me about the upgrade I switch the router (a Thomson 585 v7) off for a couple of minutes this morning and then back on. According to the customer portal my BRAS profile is now 7150 with a sync rate of 8128 which, if memory serves, is the maximum that you can get on an up to 8Mb service.This is matched by the router stats:

Uptime:	0 days, 1:04:33
DSL Type:	G.992.1 annex A
Bandwidth (Up/Down) [kbps/kbps]:	448 / 8,128
Data Transferred (Sent/Received) [kB/kB]:	0.00 / 0.00
Output Power (Up/Down) [dBm]:	12.0 / 19.5
Line Attenuation (Up/Down) [dB]:	23.0 / 36.0
SN Margin (Up/Down) [dB]:	23.0 / 5.

However this isn't being borne out by the actual download speeds I'm seeing. These are still sitting round the 1.4 Mb/s I saw before I switched of the router.

So, anyone have any idea what on Earth is going on?

Hi,

QTN: So, anyone have any idea what on Earth is going on

ANS:- YES! this is because your forgetting that 21CN ADSL2+ connections are totally controlled by the BT automated line management system. Also when your connection is regraded (moved) to 21CN it required a totally fresh line training phase i.e. this takes up to 10 days.  The ALMS has to rebuild your new connections profile i.e. it has to create a fresh BRAS profile so what you see initially may not be accurate, you will only know over time when the ALMS has had enough time to do its thing.

**If your connection speed have dropped they may well recover over time.

Ivan