pcrf 26 an aspect of session proxying is required to do this and the api 40 has to act as an application gateway function proxy and hold the diameter session to its logical completion there is an aspect of notification handling from the pcrf 26 which the api 40 must relay back to the first application 42 the diameter session is between the pcrf 26 and the api 40 rather than between the pcrf 26 and an application function directly with diameter messages from the pcrf 26 being translated into http notification messages by the api 40 before being sent to the first application function 42 and http response messages being translated into diameter messages by the api 40 before being sent to the rest of the pcrf the api 40 determines where to send the http notification messages i e the address of the http server component of the first application 42 from the application specific data encoded in the diameter session id of the diameter message and from the application settings provisioned by the application provider 56 characterizing features of the api 40 are an easy to use interface providing abstractions to complex data control attributes use of commonly used internet protocols.