Large scale information dissemination systems are typically composed of a large number of nodes and require the broadcast of data to a group of members. Group communication . To deal with these problems, there has for more than a decade been put considerable research effort into the management of groups of objects processes and the communication between them. This is referred to as group communication. 50 - 97, April 1996.
Topics represent keywords, to which participants can publish notifications and subscribe to.
As previously mentioned, topic based publish subscribe is very similar to the concept of groups. To enforce high throughput, IP multicast or a wide range of reliable multicast protocols are commonly employed. Group communication . Their definition does not apply in our case since different messages have distinct collections of possible witness sets. Implementing reliable broadcast in an insecure environment with arbitrary failures incurs inevitable overhead required for maintaining consistency.