Performance evaluation of a real-time transport protocol with deterministic and statistical QoS guarantees

In this paper, we study the performance of a real-time transport protocol in an interactive multimedia data network. Access multiplexers, which support groups of users, and digital media servers (MS) are interconnected by a star-topology asynchronous transfer mode (ATM) virtual path crossconnect (VPX) network. The network traffic is generated by data retrieval requests from data on demand (DOD) and video on demand (VOD) users. Typical DOD applications are interactive games, interactive home shopping, etc. Some VOD (like a start up) and all DOD data transfers are caused by user action. Transmissions of information packets from MSs to users are scheduled by the multitoken exchange (MTEX) protocol which represents a deadline priority on-the-fly virtual path rereservation scheme. Statistically guaranteed quality of service (QoS) is assigned to all data transmissions caused by user actions, while deterministic performance requirements are imposed to ensure the integrity of video signals. The performance of the proposed protocol is evaluated in terms of meeting the deterministic and statistical QoS requirements by means of the probability of missing the data delivery deadline and the average response time correspondingly. We show that the attainable statistical multiplexing gain depends on the number of active VOD users and on a number of other traffic related parameters.