Fault Tolerance in Application-Level Multicast Networks

Overlay multicast (Application-Level Multicast (ALM)) constructs a multicast delivery tree among end hosts. Unlike traditional IP multicast where the internal tree nodes are dedicated routers which are relatively stable and do not leave the multicasttree voluntarily, the non-leaf nodes in the overlay tree are free end hosts which can join/leave the overlay at will, or even crash without notification. So, the leaving node can leave suddenly and cannot give its descendants (and the Rendez-vous Point (RP)) the time to prepare the recovering (the reconnection) of the overlay tree, and so there is a need to trigger a rearrangement process in which each one of its descendants should rejoin the overlay tree. In this case, all of its downstream nodes are partitioned from the overlay tree and cannot get the multicast data any more. These dynamic characteristics cause the instability of the overlay tree, which can significantly impact the user. A key challenge in constructing an efficient and resilient ALM protocol is to provide fast data recovery when overlay node failures partition the data delivery paths. In this paper, we analyze the performance of the ALM tree recovery solutions using different metrics.

A New Fault Tolerance Protocol in Application-Level Multicast Networks

Application-Level Multicast Networks are easy to deployment, it does not require any change in the network layer, where data is sent to the network via the built-up coverage of the tree using a single-contact transmission of the final contract, whoare the hosts are free can join / leave whenever they want it, or even to leave without telling any node so. Causing the separation of the children of the leaved node from the tree, and the request for rejoin, in other words, these nodes will be separated from the overlay tree and cannot get the data even rejoin. This causes the distortion of the constructed tree, and the loss of several packets which can significantly impact the user. One of the key challenges in building a multi-efficiently and effectively overlay multicast protocol is to provide a robust mechanism to overcome the sudden departure of a node from the overlay tree without a significant impact on the performance of the constructed tree. In this research, we propose a new protocol to solve problems presented previously.