Abstract
A packet-based network to provide telecommunication services independent from the underlying access and transport technologies is known as a next generation network. An IP multimedia subsystem (IMS) provides an architectural framework for the next generation networks and includes variety of services such as presence, instant messaging, push-to-talk over cellular, multiparty conference, and so forth. IMS-based instant messaging is available in two flavors (immediate messaging and session-based messaging). Both flavors are subject to different types of security threats. An attacker can generate an immediate messaging flood by sending enormous number of messages to deny the services to a group of users or to an individual. Session-based messaging is facing threats such as invite flooding attack, session modification attack, and session teardown attack. In this paper, we developed a security mechanism, consisting of three layers, to secure the messaging service from flooding attacks and session-based attacks and the like. The simulation results show a good improvement in the existing security mechanism of the IMS-based instant messaging service.