Maybe Im missing something, but I'm not quite sure how you are going to connect to an ATM DSLAM using PTM and without a PVC.
ADSL1 /2/2+ use ATM DSLAMs
BT uses VC-MUX (Virtual Circuit Multiplexing) on its DSLAMs although I think TT may use the older LCC which still needs a VCI
Layer 2 is 'dumb' routing - no IP addressing - hence why the need for a virtual circuit (PVC) and use of virtual paths.
Here in the UK when setting up a router with ATM we use VPI 0 and VCI 38.
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FTTC uses IP DSLAMs. Still layer 2 routing but uses designated VLANs.
When setting up a PTM connection we have to input the VLAN info - see
IEEE 802.1q which is ethernet specific.
As soon as you select PTM it should ask for VLAN info - See my setup guide
here. Note also Openreach uses 802.1p which is a QoS extension for 802.1q. I think both BT and TT have to be set at 1 because of IPTV services.
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The way you configure ATM and PTM are different.
An ATM DSLAM will be expecting the Virtual Circuit ID (VCI) to handshake, its not going to understand any IEEE 802.1x info.
The mode protocols are different and you cant mix and match from one protocol suite with bits from another.
Its kinda like asking an FTP client to be able to read HTTP traffic.