In a framework of networks including at least a service policy decision point S-PDP (4), a network resource policy decision point NR-PDP (8), a user resource policy decision point UR-PDP (14), a P-CSCF or S-CSCF (13 or 7), a SGSN (12), and a GGSN (11), the method includes the following steps:

• transmitting the characteristics corresponding to the qualities of service QoS as provided for in a home network (2) to a visited network (3);
• extending the SIP/SDP messages to pass QoS characteristics related to a user, between a home network S-CSCF (7) and a visited network P-CSCF (13) or between a user equipment (15) and a visited network P-CSCF (13);
• using QoS received for a user calling from visited network (3), to enforce a visited network resource policy consolidated with the home network service policy, in the visited network during a multimedia communication session.