The invention provides a method and system for routing a message or a set of messages or a session from a first equipment connected or registered to a first network, to a second equipment connected or registered to a second network. The first network includes a network entity which checks requirements of the message or set of messages or session, and decides on the routing depending on the check result. The checked requirements may include media requirements of the message or set of messages or requested session. The checked requirements can also include QoS requirements of the message or set of messages or requested session.