Better-Than-Best-Effort Class for the GEOCAST Project

This paper presents an access scheme for a class of service, named Better-than-Best-Effort (BBE), optimised for supporting non real-time traffic over a geostationary (GEO) satellite ATM (Asynchronous Transfer Mode) network. The BBE class has been designed to also efficiently support multicast traffic. In ATM frameworks, the IP traffic is mapped onto ATM connections, each one belonging to a pre-defined class of service and characterized by several QoS (Quality of Service) parameters, describing its behaviour in terms of the bandwidth and delay requirements. Since the traffic characteristics are often unknown (e.g., for most multicast and best-effort IP traffic), the connections of the proposed class of service require only two simple parameters: the amount of bandwidth to be reserved and the desired average delay. The reserved bandwidth is accessed on-demand, so that if the BBE connections do not request the full bandwidth, the leftover capacity can be distributed among the best-effort connections. Through the application of control theory methods, the Bandwidth-on-Demand (BoD) scheme developed for the BBE class of service can regulate usage of the satellite bandwidth to ensure the delay requirements. OPNET simulations have been executed to evaluate the impact of the proposed scheme.