A method and system for providing services in communications networks. A gateway layer determines information about a communication session and responsively sends a signaling message to a session manager, providing the information. The session manager may then send a signaling message to a service agent, also providing the information. The service agent may in turn apply a set of service logic based at least in part on the information, so as to derive a service treatment, and the service agent may send a signaling message so as to cause an enforcement engine (such as the gateway or session manager) to carry out the service treatment. Advantageously, this arrangement may facilitate imposition of services across various types of communication sessions (such as voice sessions and/or data sessions) and access networks (such as circuit-switched and/or packet-switched), at session initiation and during the course of an ongoing session. A variety of useful services may thereby be provided.