While a multicast message is to be delivered to multiple destinations, only one copy of the message is transmitted along a given network segment on its path to these destinations. The processing and traffic levels are less than if each recipient’s message were transmitted individually.
Multicast traffic can require security protection, whose nature and strength vary based on the multicast group’s purpose, characteristics, and membership. Numerous secure multicast protocols have been proposed. Some are applicable to any multicast group but have restricted computational feasibility and scalability; others are optimized for the characteristics of a particular group. Some have been tested under wide-scale deployment; others are still experimental or theoretical. A single secure multicast protocol that is computationally feasible and scalable for all groups, all senders, and all receivers remains a research goal. Additional work is needed to determine the requirements, applicability, scalability, and security characteristics of the various approaches.