The Interworking between the IMS PCRF and the eCNS280 is as
follows:

The
eCNS280 and the eAPP610 in the eLTE system communicate with the IMS
system through the following interfaces:
· Gx: Used by the PCRF to deliver commands for installing or
deleting service-related policies to the P-GW and used by the P-GW to report
bearer events to the PCRF.
· SGi: Used for exchanging messages between the UE and the IMS
system without parsing messages.
· SIP: Used for interconnecting with the SIP server in the IMS
system to transparently transmit messages and data