PPP is a fairly generic option negotiation mechanism. The HDLC framing can be omitted, though. They realize perfectly well that ours is the only approach which can actually make larger configurations of their gear useful.
Huge capacity is useless unless there's a way to switch it.
Essentially, an ADM on a card. There's a bunch of vendors selling OC-3 SARs. Of course, Fast Ethernet is cheaper yet, but it doesn't mix well with telco transmission facilities. 32-bit CRC at the end.