Session Initiation Protocol (SIP) h as been widely applied to telephony service. SIP is also adopted as the signal communication protocol of VoIP and 3GPP, so the development of SIP receiving much concern. Currently the research of SIP can be divided into four issues, including terminal mobility, session mobility, personal mobility, and service mobility. In this paper, we address the issue of session mobility. We want to solve the problem allowing a user to transfer, split, and retrieve a session over multiple devices by using SIP. In order to provide the service, three new agents have been introduced based on the definition of user agent proposed in RFC 3261. There are session manager, session user, and free node. Based on these agents, we propose a complete mechanism, to transfer and retrieve a session over multiple devices. According to our mechanism, the user will facility transfers, splits, and retrieves a session over multiple devices. Finally, we implement the mechanism by modifying the open source project of "Sip-Communicator".

SUMMARYOne of the most important research subjects in session initiation protocol (SIP) is mobility management. Session mobility is a key issue in SIP mobility management. Session mobility is an advanced feature that maintains an ongoing media session from one device to another. In this paper, we consider the issue of session mobility and propose a complete integrated solution, referred to as 'session integration service', to transfer an ongoing media session over multiple devices. To provide flexibility in session mobility, three new agent states are introduced based on the user agent definition. They consist of session manager, session user, and free node. This paper also proposes two split session integration methods for session integration service based on these three agents. The proposed method provides session mobility flexibility and allows the user the ability to transfer, split, and retrieve a session over multiple devices. Moreover, the split session can be integrated in any devices. To ensure session mobility over multiple devices, the session integration service will be implemented through a modification of the open source project 'SIP-communicator'.