The present invention provides a service node, which extends the services of a carrier's multimedia subsystem (MS), such as an IP multimedia subsystem (IMS), to enterprise networks in an efficient and effective manner. As such, MS subscribers gain access to enterprise services in addition to the carrier's services provided via the carrier's circuit switched subsystems (CS) and packet subsystems (PS). The service node acts as a liaison between enterprise application servers and the MS, such that the enterprise application servers appear as MS application servers to the MS. The service node provides user identifier and protocol translation between enterprise and MS user identifiers and protocols, respectively. As such, enterprise application servers can access the MS as well as be accessed by the MS to support user mobility, with continuity of services, between the enterprise and carrier networks.