National Cheng Kung University
Voice over IP (VoIP) is one of the most popular Internet applications. Many VoIP protocols (e.g. SIP) are based on a central-server scheme in which a caller needs to query the central server first for the callee's information (e.g., IP address) before it can connect to them. However, such a centralized architecture has some drawbacks, such as an unbalanced load and a single point of the failure. As a result, some researchers have proposed the use of Peer-To-Peer (P2P) techniques for VoIP communication. However, compared to a centralized approach, setting up a VoIP connection over multiple hops could potentially take a longer time and might discourage users from utilizing this service.