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In an enterprise network, it is common to have hundreds of video conferences held simultaneously such that a large number of video streams need to be transmitted between participants in different geographical locations. For such a large transmission demand, an advance reservation (AR) system deployed for the video conferencing system can provide quality-of-service (QoS) guarantees to users and improve the resource utilization of the network. However, the effective resource reservation strategies for a heavy traffic case still remains open. In this paper, we propose an algorithm called the elastic timeslot-based advance reservation algorithm (ETARA), which aims at improving the resource utilization and reducing the computational complexity. A new time processing method, elastic timeslot, is proposed for the time domain management. Moreover, ETARA takes not only the processing time but also the resource usage into account. Comparative simulations with the existing two popular approaches, the dynamic timeslot-based approach and timeslot-based flexible approach, have been performed in terms of the acceptance ratio and runtime. The results show that with the same acceptance ratio, the runtime of ETARA can be up to 57 times lower than that of the flexible timeslot-based approach. Though ETARA has a slightly longer runtime than the dynamic approach, the acceptance ratio of ETARA can be twice as high as that of the dynamic timeslot-based approach.

In an enterprise video conferencing system, the enterprise network can be shared by hundreds of video conferences. On the other hand, participants may not arrive at the same time and stay until the end of the conference. The abilities to reserve resources in advance, as well as effective dynamic multicast when participants can join and leave the conference at any time, are essential in the distributed multi-party video conferencing systems. However, the effective advance reservation strategies of the dynamic multicast requests for a heavy traffic case still remains open. In this paper, we investigate the problem of Maximizing the number of admitted Dynamic Multicast requests in the Advance Reservation environment (MDMAR) for the enterprise video conferencing system. We take two path schemes of a fixed path and variable paths, as well as a heterogeneous bandwidth reservation model into account. Firstly, we prove that the MDMAR problem is NP-complete and formulate it mathematically as an integer linear program (ILP) for small networks. Then, we develop greedy algorithms and simulated annealing (SA) algorithms for enterprise networks. Comparative simulations are performed to evaluate the heuristic algorithms for both small networks and enterprise networks. We find that the SA algorithms can provide within 6% lower optimal solutions than the ILP algorithms for our small network, and up to 10% improvement over the greedy algorithms for the large campus or enterprise network.