MAMBO: Membership-Aware Multicast with Bushiness Optimisation

Multicast is a key component of applications such as multimedia streaming, multi-player gaming and generic publishsubscribe and event notification services. IP multicast has a number of technological, practical, and business obstacles [3], and thus is not widely used. An alternative, ApplicationLevel Multicast (ALM), has been proposed to support similar functionalities. A survey of existing ALM systems [5] indicates that many ALM systems are built on P2P overlay infrastructures and construct multicast trees among application participants, e.g. Scribe [2] uses Pastry [6]. This article presents Membership-Aware Multicast (MAM) and MAM with Bushiness Optimisation (MAMBO), which reuse the communication structure of a tree-based ALM system to track group membership, i.e. to record when peers join or leave the group. MAM and MAMBO are implemented on Scribe with Pastry and a series of experimental results compare performance with a conventional serviceprovider architecture. We show that MAM and MAMBO quickly detect, and effectively manage, the arrival and departure of peers. In addition, MAMBO delivers a number of other advantages. The Bushiness Optimisation limits the overhead placed on any peer, hence preserving the scalability of the ALM system. The implementation as Scribe policy plug-ins illustrates that MAMBO can readily be overlapped on any tree-based ALM, and requires few changes to the underlying technology.