206 Category: Artiicial Intelligence INTRODUCTION The article presents an approach to optimize the multicast transport protocols. The main constraint of this procedure is the orthogonality (linear independence) of protocol parameters. Protocol parameters are variables deined for protocol classes, where the possible values of each parameter are protocol mechanisms, which serve the same goal in the multicast transport protocol. A multi-dimensional hyperspace of protocol parameters is stated, as a mathematical model of the optimization process where every transport protocol is represented as an individual point. A multicast transport Simulator for multiCast (SimCast) has been developed to describe the performance of the transport protocols and to simulate the operation of these protocols for reliable multi- casting. The simulator supports the protocol analysis in the hyperspace of protocol parameters. BACKGROUND Reliability is one of the most important features of all mul- timedia applications. This requirement may be especially critical in case of multicast, where the timely correction or resending of lost data is even more dificult because of the large volume of data to be transferred. Multimedia applica- tions make multicast an active area of research. Multicast- ing is the one-to-many group communication way. For this purpose the IP-multicast transport is the preferred mechanism (Hosszú, 2005). Since most of the multicast applications are media-related software, for example, media conference, voice distribution, shared whiteboard, and various collaborative media tools, they need more reliability than the best-effort delivery of Internet protocol (Adamson & Macker, 2001; Luby, & Goyal, 2004). In order to increase the reliability of multicast ap- plications additional multicast transport protocols are used to achieve the required level of reliability (Whetten & Tas- kale, 2000). Such a protocol is the NORM: NACK-Oriented Reliable Multicast Protocol (Adamson, Bormann, Handley & Macker, 2004a, 2004b). It is hard to compare the various protocol mechanisms implemented in different protocols. Therefore, the modularly structured simulator SimCast (Simulator for multiCast) is developed for trafic analysis of unicast (one-to-one) and multicast (one-to-many) streams (Orosz & Tegze, 2001). To carry out the necessary analysis of the unicast and multicast trafic, a well usable simulation program should be applied in order to present statistically correct results for multicast data transfer. The reason of developing a new, custom simula- tor instead of using a standard framework like ns (Breslau, Estrin, Fall, Floyd, Heidemann, Helmy, Huang, McCanne, Varadhan, Xu, and Yu, 2000) is that the architecture of the SimCast simulator is optimized for transport layer model- ing and, due to its modular design, it is relatively easy to integrate new protocol mechanisms in it. DECOMPOSITION OF THE MULTICAST TRANSPORT PROTOCOLS Multicast transport protocols have many different proper- ties for data delivery. These attributes can be represented by the previously mentioned protocol parameters (Hosszú, 2005). Each protocol parameter speciies different reliability mechanisms for the same delivery attribute. Such a protocol parameter is, for instance, the repair method, which can have the values like “retransmission”, “forward-error correction”, “interleaving”, or different ways of “local receiver-based repairs” (Luby & Vicisano, 2004). Another parameter is the An Approach to Optimize Multicast Transport Protocols Dávid Tegze Budapest University of Technology and Economics, Hungary Mihály Orosz Budapest University of Technology and Economics, Hungary Gábor Hosszú Budapest University of Technology and Economics, Hungary Ferenc Kovács Budapest University of Technology and Economics, Hungary Copyright © 2009, IGI Global, distributing in print or electronic forms without written permission of IGI Global is prohibited.