PIK - Praxis der Informationsverarbeitung und Kommunikation
Fachzeitschrift für den Einsatz von Informationssystemen
Ed. by Müller, Paul
Currently the most prominent service on SIP basis is Voice over IP (VoIP). Despite its growing popularity, it has not yet been able to substitute the “good old” Public Switched Telephone Network (PSTN). Security, reliability, emergency calls and SPAM over IP Telephony (SPIT) are issues that have not yet been solved satisfactorily. In our approach, Cooperative SIP (CoSIP), we address two important issues: reliability and security. CoSIP is a hybrid architecture based on a Peer-to-Peer (P2P) network cooperating with central servers. The P2P network consists of SIP User Agents (UA) that organize themselves in a Distributed Hash Table (DHT). Both the DHT and the server manage user registrations and session establishments in parallel. While the P2P network provides better service reliability and robustness against denial of service (DoS) attacks, the server provides improved security for the overall architecture and a better lookup performance. Our new architcture uses both technologies in parallel to combine advantages from both concepts, leading to improved reliability, security and performance. Our prototype implementation of CoSIP acts as a local SIP proxy and can be used with standard SIP clients. The proxy implements the additional CoSIP functionalities. We successfully validated the functionality of CoSIP on PlanetLab.