An Improvement On PIM-SM For The General Hardware Platform

With the continuous development of broadband multimedia networks, applications of broadband networks emerge in endlessly. IPTV, video conferencing, data and information distribution, network audio applications, network video applications, multimedia, distance education and other broadband applications pose a challenge to the capacity of broadband multimedia networks Instead of meeting the requirements on both emerging broadband network applications and network bandwidth quality of service, the traditional network based on the unicast technology cause many problems including network latency, data loss and so on. These problems can be resolved by multicast technology. In the multicast network, there is no need to increase the network bandwidth for the backbone network even if the number of multicast users is doubled.As a newer way in data transmission, IP multicast has the advantages of high efficiency, low bandwidth consumption and wide range of applications. PIM-SM has a pivotal position in the IP multicast architecture as the most widely used multicast routing protocol Therefore, how to improve the efficiency in the process of multicast packet forwarding by integrating multicast routing and multicast forwarding mechanisms is currently the subject of extensive discussions. This paper analyzes the PIM-SM protocol and proposes an improvement method based on the general hardware according to the status that many constraints exist in the protocol implemented on the current layer2and layer3devices. Meanwhile, a series of further improvements are proposed based on the basic improvement and the result of experience shows that the improvements comply with the standard of versatility, compatibility, reliability and efficiency. The main contribution of this paper is as follows:First, this paper takes the analyze on the current implementation framework and architecture of Layer3multicast protocol software and proposes a set of frame forwarding model which is compatible with a variety of3-layer multicast way. The model is divided by3-layer multicast software into multiple levels, each level of constructs and maintains its own multicast table entry. Meanwhile, the model distributes the multicast packet forwarding process into different levels according to the characteristics of each level.Second, this paper proposes an improvement algorithm based on the general hardware according to the status that many constraints exist in the protocol implemented on the current layer2and layer3devices. This improvement get over the constraints by imitating (*, G) forwarding using the extended (S, G, rpt) entry. Third, this paper extends the interface set of the protocol entry based on the improved PIM-SM protocol algorithm; then, it modifies the algorithm for adding or deleting the interface in (*, G),(S, G) and (S, G, rpt) state machine according to the expanded set of outgoing interface list which ensures the consistency of entry in the improved protocol when it changesFinally, tests on feasibility and efficiency are ran, which shows that the new implementation based on the new3-layer multicast frame model effectively shields from the complexity in the multicast packets forwarding caused by the differences in the hardware implementation, achieving the support on both software packets forwarding and hardware packets forwarding, and ensuring the protocol software’s efficient and reliable.