Ongoing Multicast Session Research Articles

Directional core selection approach and dynamic tree reorganization for delay and delay variation multicast routing

SummaryMulticast communication constrained by end‐to‐end and interdestination delay variation is known as delay and delay variation–bounded multicast. These constraints are salient for real‐time multicast communications. In this paper, we propose a directional core selection algorithm for core selection and delay variation–bounded multicast tree generation. Another algorithm, based on k‐shortest paths, is proposed to further decrease the interdestination delay variation of the trees generated by directional core selection. We also propose the dynamic version of both algorithms that respond to dynamic join and leave requests to the ongoing multicast session by reorganizing the tree and avoiding session disruption. Simulations show that the proposed algorithms surpass existing algorithms in end‐to‐end delay, interdestination delay variation, execution time, and failure probability.

P2P transfer of partial stream in multimedia multicast

In this paper, we propose a new multicast scheme that is based on the client-initiated-with-prefetching (CIWP) and peer-to-peer (P2P) transfer of a partial multimedia stream. In the CIWP scheme, when a new client joins an ongoing multicast channel, the server has to create an extra unicast channel to retransmit the partial stream that has already been transmitted. However, the unicast channel consumes some of the I/O bandwidth of the server, as well as some of the network resources between the server and the client's Internet Service Provider (ISP). To solve this problem, we propose the use of the P2P transfer algorithm to deliver the partial stream from a client that has already joined the ongoing multicast session to the newcomer. This P2P transfer between clients is limited to clients belonging to the same ISP. To further improve the performance, a threshold is used to control the P2P transfer. We performed analytical studies to show that the proposed multicast scheme can reduce the consumption of the network resources of the server, by utilizing the client's disk space. We also performed various simulation studies to demonstrate the performance improvement in terms of the use of the server's bandwidth and the waiting time for the clients’ requests.

Threshold-based multicast for continuous media delivery

In this paper, we propose and evaluate the performance of a continuous media delivery technique, called threshold-based multicast. Similar to patching, threshold-based multicast allows two clients that request the same video to share a channel without having to delay the earlier request. It ensures sharing by permitting the client with the later arrival time to join an ongoing multicast session initiated for the earlier request. However, threshold-based multicast does not allow a later arriving client to always join an ongoing multicast session. If it has been some time since the ongoing multicast session was started, a new multicast session is initiated. That is, a threshold is used to control the frequency at which new multicast sessions are started. We derive the optimal threshold that minimizes the server bandwidth required. Our analytical result shows that threshold-based multicast significantly reduces the server bandwidth requirement. Furthermore, we perform a simulation study demonstrating the performance gain of continuous media delivery by threshold-based multicast.