Optimization For PIM-Snooping Protocol

With the continuous development of networks technology, more and more layer-3 switches with high-speed forwarding capability are used in the networks. In existing layer-3 switch system, when a lay-3 switch wants to forward multicast data through a VLAN, it broadcasts the multicast datagram to all the layer-2 ports in the VALN. As a result, the multicast traffic reaches some downstream routers which don't need it. It leads to a waste of resource. In order to achieve the layer-2 forwarding management of PIM, PIM-Snooping was proposed. PIM-Snooping realizes forwarding multicast datagram exactly in VLAN by snooping PIM protocol messages.After analyzing how PIM-Snooping worked in PIM-SM scenes, this paper pointed out that PIM-Snooping spent a lot of protocol overhead, for it didn't support join suppression in LAN. Based on the exsiting PIM-Snooping, this paper proposed a solution by restructuring PIM protocol messages, and described the improved scheme in detail. At last, this paper did some simulation about the improved scheme, and the result of simulation showed that the improved scheme could reduce the protocol overhead, when LAN existed.This paper also did research about the application of PIM-Snooping in actual networks. For fragment packet caused by downstream's joining many multicast groups, this paper proposed to treate the port receving fragment packets as fragment port, and analyzed the performance of this mechanism by simulation. For the security risks of hacker attack, it may create a lot of useless downstream state entries and caused the normal entries couldn't be created. This paper proposed a process mechanism by dynamic interaction with the PIM routers to eliminate the security risks, and also expounded the mechanism in detail to prove its feasibility and effectiveness.