Patent ID: 8295176

Claim:
A method comprising: receiving, at an Internet Protocol Multimedia Subsystem (IMS), a message to request a communication through a packet switched network, where the packet switched network includes a core network associated with the IMS and an access network that provides access to the core network; determining, by the IMS, whether a sender designated the message as a priority message; when the sender designates the message as the priority message: identifying, by the IMS and in response to determining that the sender designated the message as the priority message, a first resource availability through the packet switched network and a second resource availability through a circuit switched network, where identifying the first resource availability includes: determining, via a resource access control function (RACF) associated with the IMS, resource availability and topology information for the access network, determining, via the RACF, resource availability and topology information for the core network, and determining the first resource availability based on the resource availability and topology information for the access network and the resource availability and topology information for the core network, and establishing, by the IMS, the communication through one of the packet switched network or the circuit switched network based on the first resource availability through the packet switched network and the second resource availability through the circuit switched network; and when the sender does not designate the message as the priority message, establishing the communication through the packet switched network without identifying the first resource availability through the packet switched network and the second resource availability through the circuit switched network.