IMS -- Underlying Models

"Walled Garden" Architecture/Business Model
Theory: Avoid the "Bit Pipe" Syndrome
That is, the (perceived) commoditization of bit transport
Every SIP packet inspected by at least one CSCF
Consider what this means for the end-to-end principle
And what kind of state storage/maintenance might be required

Holy Grail: One Platform, Many Services
Presence and Availability
PoC (Push to talk over Cellular; PTT was taken :-)
PoX (Push to X)
Voicemail, Show (video), etc
Peer to Peer
IM
and eventually
Wireless/Wireline integration  
e.g., dual-mode voice