An IMS Restoration System with Selective Storing of Session States

Takeshi USUI  Yoshinori KITATSUJI  Hidetoshi YOKOTA  Kiyohide NAKAUCHI  Yozo SHOJI  Nozomu NISHINAGA  

IEICE TRANSACTIONS on Communications   Vol.E97-B   No.9   pp.1853-1864
Publication Date: 2014/09/01
Online ISSN: 1745-1345
DOI: 10.1587/transcom.E97.B.1853
Type of Manuscript: PAPER
Category: Network
restoration system,  IMS,  SIP,  network operation,  

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It is known that the IP Multimedia Subsystem (IMS) provides various telecom services e.g., VoIP, instant messaging, and video conferencing. In the IMS, these services are provided with session initiation protocol (SIP) handled by call/session control function servers (CSCFs). Completing the SIP signaling call flow without delay is vital to provide satisfactory services to the users. For service continuity, previous studies redundantly synchronized session states of CSCFs with backup servers. This paper proposes an IMS restoration system that selectively stores the session states. This is achieved by utilizing the retransmission mechanism of SIP. Time-based simulation emulating the process of backup servers shows that the proposed system reduces the number of backup servers to less than 38% compared to the previous studies, without degrading the service quality.