We have presented the issues arising from real time continuous media support and multicasting in packet networks, with an eye towards the interactions between the two. The heavy demands of continuous media on any network have motivated research in many areas, with multicasting being one of the most active, due to its potential for large economies. Apart from the problems that are specific to either multimedia or multicasting, there are special issues that become more important when the two are combined. Fortunately, the nature of continuous media gives rise to some special case solutions, which can be exploited to our advantage.
Issues such as bandwidth and delay requirements, error tolerance, statistical guarantees and heterogeneity, create a complex environment that must be supported in an efficient and flexible way. Probably, the most important research issues revolve around the core theme of open loop, preventive or anticipatory, mechanisms vs. the traditional closed loop, corrective ones. The exact mix of these two modes of operation achieving the desired quality of service and flexibility with minimum cost is one of the most interesting topics for further research.