@ 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