The Research On A Protocol Of Application Level Multicast For Distance Learning

In this paper, the main characteristic of multi-point communication that has a lot of interactive information of distance education in Internet is analyzed firstly, and some basic principles to design multi-point communication protocols for distance education system are proposed. Furthermore, based on above principles we analyzed and compared several reliable multicast protocols and application level multicast protocols, and investigated their superiority and deficiency.Based on above research, a new application level multicast protocol which is called Scalable Hybrid Multicast (SHM) is designed. SHM concludes an address scheme, a tree-mesh topology management protocol (STMP) and a content distribution protocol (SCDP).To solve the problems of IP multicast address and the deficiency of existing application level multicast protocols' address scheme, we proposed a new address scheme. To organize the members of a group into a overlay network more efficiently, two new methods which are "active members" and control of the depth of tree are put forward. We have done some simulation experiments using NS-2, the results of the experiments show that these methods can improve the efficiency of the tree-mesh topology, and can reduce the cost of resource and the delay of join. Distribution of the data over the overlay network is also an important portion of SHM, we proposed a data naming mechanism, an error control mechanism and a simple but flexible mechanism of flow control in SCDP.