AT&T's demarcation point for DSL service is the loop jack on your premises. If you order the managed router option on AT&T's SDSL service, the demarcation point will be the Ethernet port on the DSL router.

there is none

Line of demarcation is where the point where ownership of the communications equipment changes from the communications carrier to the user.

POP is the point where the customer connects the network data traffic to the communications carrier.

The point where your ISP's network connects to your network

The Demarcation point