The Research Of Multicast Protocol In Link Layer Based On Igmp Snooping

Recently in multicast net, when router transmits multicast message to link layer Switch on the edge of receiver layer, as traditional link layer Switch, it will broadcast multicast message. In this way it not only wastes plentiful net bandwidth, arouse broadcasting storm, but also infect normal operation. Therefore, it is compelled to realize rational multicast mechanism in link layer Switch.Against this instance, the author deeply research the multimedia multicast communication mechanism in Switch Ethernet, designs link layer multicast protocol based on IGMP Snooping in SwitchEthernet, and validates the protocol by experiment.IGMP Snooping protocol monitors IGMP news in network, acquires multicast group message of ports using IGMP message detected, and sets up a VLAN for each group. In the network linked by VLAN ports, there is at least one group member or contains multicast Router. Protocol will dynamic maintain the entering and exiting of the host computer in this port collection. Thus, when multicast data package is transparent, it is just transparent in its multicast VLAN port and will not be broadcasted other ports that needn't multicast data, In this way, bandwidth is saved. Meanwhile, on the precondition of keeping transparent to multicast Router, the Ethernet Switch completes function of IGMP agent, filtrates unnecessary IGMP news and prevents "IGMP Report Flooding".Advantage of using IGMP Snooping lies software and hardware of Switch and Router needn't any modification. Only software realization modules of IGMP Snooping need to be added to provide realization of net layer in link layer, and enlarge multicast bound to brim subnet.