Where are we with SUPL?


PS:
Control Plane = too expensive and "pushy"

Uses the Circuit Switched network (TCH) for assistance data and communication
Requires updates to several network elements to handle all of the standard protocols
Supports legacy terminals (excepting AGPS)
Supports location of emergency calls

User Plane = the commercially viable pull option

Uses the Packet Switched network (TCP/IP) capability to bypass the Switched Circuit infrastructure
Modification of network not required
Cannot locate legacy terminals
Does not support location of emergency calls

See
Dueling Architectures: User Plane, Control Plane (PDF)