Use 2 level label stack for scalability. Customer tunnels only seen by edge devices. Want to do sequencing and take care of little quirks. Need a protocol specific header. Plus some semantic translation, e.g. mapping ATM CLP bits into EXP bits so we can do intelligent things.
Static mapping is possible.
Circuit status is signalled using label mapping. VC FEC TLV, want to do some compression of withdrawls like to converge on a single message. VC-ID identifies the circuit. Group ID can identify the port or the virtual tunnel. Control word contains sequence number.