A multipoint videoconferencing system is composed of four main components that are user interface

codecs

conferencing control and media transmission architecture.Among them

the media transmission architecture is most critical for a videoconferencing system.Traditional methods have many drawbacks such as high network resource overhead

heavy burden on terminals

low scalability and complicated control.This paper proposes a principle for design of videoconferencing

which makes the system simple

robust

feasible and scalable.According to the principle

a new model of multipoint videoconferencing based on multiple source-specific multicast trees is given.This model leads to simplifying design of the videoconferencing

reducing the overhead of networking resources and rising scalability.The paper introduces the evaluation method for transmission architectures

comparison of three types of traditional structures

the new transmission model and a practical videoconferencing developed by the anthers.