Security issues in multicast communication have rarely been touched upon to date. We believe that wide-area multicast communication is at a substantially increased risk from specific security threats, compared with the same threats in unicast. This arises both from the lack of any form of effective group access control, and from the fact that multicast traffic traverses potentially many more communication links than does a single unicast communication, thereby creating more opportunity for a link attack. We discuss specific threats that are relevant to multicast, and explain why they are so. We propose security mechanisms specifically for multicast groups requiring safeguards that afford protection against some of these threats. More precisely, we propose a version of the IGMP protocol that can reliably enforce subnet-level group access control. We also describe a scalable mechanism to control multicast traffic in transit that can, for example, prevent a misbehaving source from causing undue congestion over the wide-area.>

One of the central problems in one-to-many wide-area communications is forming the delivery tree - the collection of nodes and links that a multicast packet traverses. Significant problems remain to be solved in the area of multicast tree formation, the problem of scaling being paramount among these.In this paper we show how the current IP multicast architecture scales poorly (by scale poorly, we mean consume too much memory, bandwidth, or too many processing resources), and subsequently present a multicast protocol based on a new scalable architecture that is low-cost, relatively simple, and efficient. We also show how this architecture is decoupled from (though dependent on) unicast routing, and is therefore easy to install in an internet that comprises multiple heterogeneous unicast routing algorithms.