Proposal and analysis of multicast communication method in a department VPN

In recent years, VPN (Virtual Private Network) has become an important subj ect not only in the Internet, but also on intranets and extranets. The VPN enables us to communicate safety by using public networks. A number of rese archers have studied DVPN (department VPNs). Furthermore, multicasting has been attracting attention as a means to increase the volume of voice data a nd multimedia data on the Internet. However, a multicast router is needed t o deliver data with multicasting on the default network. Although it is pos sible that the IP multicast function will be added to all new routers in th e future, it is not realistic to convert all default routers in use to mult icast routers at this moment. Systems which make use of multicast servers w ithout using multicast routers have been proposed. However, many problems a rise in the conventional model, such as excess load on the multicast server , and traffic on its domain when data with multicasting are sent or receive d over the DVPN. In this paper, we propose an effective method of multicast communication over the DVPN in order to establish a secure DVPN for multic ast applications such as video conferencing. In the proposed method, the re lay function for multicast communication is added to the DVPN terminals the mselves, which leads to easy use compared to the conventional method with m ulticast server. We propose two packet delivery system models, the daisy ch ain model and the extended daisy chain model. The daisy chain model is made up of a group of DVPN hosts, which have the copy function. In the extended daisy chain model, a branch division function is added to the daisy chain model. We present a network model for numerical calculation to show the eff iciency of our proposed models. We investigate the effects of load variance , network traffic, and delay time on the performance of the two proposed mo dels compared to the conventional model, and show that the two proposed mod els are superior to the conventional model. (C) 2001 Scripta Technica.