With the advent of high-speed access network technologies such as ADSL, increasing numbers of Internet users are participating in various interactive multimedia applications. Among these, the most popular are the massively interactive on-line games, or MMPOGs. In MMPOGs, a large amount of event data is associated with various control objects. This event data has different characteristics from that which is generally used on the Internet. Namely, events occur very frequently with short inter-arrival times and their size is quite small, because they only contain control information. Most commercial MMPOGs use TCP or UDP as the transport protocol for the event data. However, since TCP is such a heavy protocol, due to its complex congestion control algorithm and byte-oriented window scheme, it is difficult to support many concurrent users. On the other hand, UDP is a relatively lightweight protocol, but there are no functions available which permit reliable transmission and session management. In this paper, we propose a new transport protocol, Game Transport Protocol (GTP), which is designed for the transmission of the event data used by MMPOGs. GTP supports several functions designed to meet the various requirements of MMPOGs. Firstly, GTP uses a packet-based window scheme not a byte-based window scheme as in the case of TCP. This scheme is quite simple and suitable for the small size of the event data. Also, GTP performs session management and retransmission using GTP control blocks, and supports an adaptive retransmission scheme that controls the maximum number of retransmissions according to the real-time priority, in order to meet the time constraints of the event data. Although GTP is a specialized transport protocol, optimized for MMPOGs, it could also be utilized as a transport protocol for other interactive multimedia applications.
Voice over IP (VoIP) is one of the advanced services supported by the next generation mobile communication. VoIP should support various media formats and terminals existing together. This heterogeneous environment may prevent diverse users from establishing VoIP sessions among them. To solve the problem an efficient media negotiation mechanism is required. In this paper, we propose the efficient media negotiation architecture using the transformation server and the Intelligent Location Server (ILS). The transformation server is an extended Session Initiation Protocol (SIP) proxy server. It can modify an unacceptable session INVITE message into an acceptable one using the ILS. The ILS is a directory server based on the Lightweight Directory Access Protocol (LDAP) that keeps user¡*s location information and available media information. The proposed architecture can eliminate an unnecessary response and re-INVITE messages of the standard SIP architecture. It takes only 1.5 round trip times to negotiate two different media types while the standard media negotiation mechanism takes 2.5 round trip times. The extra processing time in message handling is negligible in comparison to the reduced round trip time. The experimental results show that the session setup time in the proposed architecture is less than the setup time in the standard SIP. These results verify that the proposed media negotiation mechanism is more efficient in solving diversity problems.