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[waltergmw]

Gentlefolk,

I have read somewhere that once a line has been upgraded to 212CN on ADSL2+ the process is not reversible back down to ADSL1.
Can anybody confirm this?
Is it perhaps that some ISPs don't want the bother of double changes and presumably BT Openreach charges ?
Or is this a BT Openreach restriction ?

Kind regards,
Walter

[jeffbb]

Hi
I thought that 21CN is  the platform  and that you could be on ADSL1 or ADSL2+ .Might have got it wrong ?

Regrds Jeff

[razpag]

Gentlefolk,

I have read somewhere that once a line has been upgraded to 212CN on ADSL2+ the process is not reversible back down to ADSL1.
Can anybody confirm this?
Is it perhaps that some ISPs don't want the bother of double changes and presumably BT Openreach charges ?
Or is this a BT Openreach restriction ?

Kind regards,
Walter

Your kinda right Walter. They certainly DONT like to revert back once on 21CN, I can only assume that its because once everybody has 'gone over' to 21CN, they will recover the old 20CN equipment and save on costs

I have this scenario a few times a month whereby the EU has had a free migration to 21CN, but due to line length etc, the 2.2Mhz circuit wont perform anywhere near as well as it would on the old 1.1Mhz 20CN product. The EU then has to request a transfer back to 20CN. Fast-forward a week or two and I'm back at the same premises and find that what the SP has done is just 'capped' the 21CN line to 20CN speeds. This has no effect whatsoever on the performance and the original fault is still present.

Usually, the 2nd call the EU makes will see a product swap back to 20CN. It always helps the EU's cause to have good notes from the engineer to back up their request. HTH.

[waltergmw]

@ Jeff,

You are perfectly correct that 21C N uses a new set of MSANs with new line cards. In our cases I can tell immediately that a 21CN migration has taken place as the new Line cards identify themselves as Infineon (I.e. Huawie) which we've not seen here before.
Previously we had mainly TI, Alcatel, and unknown. Those EUs on Zen services reamin on ADSL1 services as we all agree that there would be a significant reduction of throughput if ADSL2+ were selected.
I have also observed that only Zen seem to have been migrated so far and that BT services on shorter lines are to be migrated to 21CN "Up to 20 Mbps" services - i.e. ADSL2+ in mid April.

We have also discovered that 21CN ADSL1 services are more stable and many marginally faster when a 2Wire 2700HGV modem is used which happens to have an Infineon chip in it too.

@ RP,

Thanks very much for that warning re capping which I was not aware of.

The problem we now face is with a PlusNet service (At variance with the Zen method) where they have accepted a request to upgrade to 21CN ADSL2+ on 5 May 2011 and will then request a downgrade to ADSL1 service.
This is obviously still new territory for the PlusNet folk and I am very keen to ensure we get the correct configuration ordered. Thankfully the 2Wire also clearly indicates whether a line is capped or not.

EDIT We have now had the ADSL2+ order cancelled and a new ADSL1 21CN
regrade ordered and successfully completed. (See also http://forum.kitz.co.uk/index.php/topic,9245.0.html and http://forum.kitz.co.uk/index.php/topic,9264.0.html)

Any other advice gratefully received.

Kind regards,
Walter

[Azzaka]

You can change back if the ISP allows it Walter.

If you are on the 21CN platform you can revert back to 8mb or 2+ on the Zen services. You can NOT revert back to the 20CN platform unless there is a serious exception with the line.

Kindest Regards,
Leo

[kitz]

The technology (adsl1/adls2+) is different than the platform (20CN/21CN).
 
Its possible on some routers to set back (downgrade) to adsl1 from adsl 2+  (ST585 for eg.... which even allows Annex_A/M (downgrade) swapping if the ISP's MSAN (Be*) allows).  
Personally the 2wire works pretty awful on my own (short) line.

[burakkucat]

I currently use a Netgear DG834Gv5 and my ISP (TalkTalk, via Opal Telecom) performed an upgrade to 21CN last year (or was it the year before?). When I signed up for the package that I currently use (no longer available to new users), it was "Up To 8 Mbps". When the 21CN upgrade took place, I noticed a small increase in both down- & upload speeds and, when I checked, found that it was now ADSL2+ but capped to 8Mbps.

For reasons irrelevant to this thread, I have just (in the last 48 hours) reconfigured the DG834Gv5's "DSL Mode" from "Auto (Multi-mode)" to "ADSL (G.DMT)" and thus have reverted back to using ADSL1 on the 21CN equipment.