Apparatuses, methods, and systems are disclosed for establishing an IP multimedia subsystem session. One method includes receiving, at a first network entity from a user device, a first session initiation protocol message comprising a session description protocol, wherein the first session initiation protocol message is used to establish an internet protocol multimedia subsystem session for an application. The method includes transmitting, from the first network entity to a second network entity, a first message comprising an internet protocol address and an identifier for the application. The method includes receiving, at the first network entity from the second network entity, a status of a radio access technology of the user device, wherein the status of the radio access technology of the user device is received by the second network entity from a third network entity.