Research On Multicast Mechanism In Wireless Broadband Special Networkof Police

Multicast technology, compared with unicast technology, has the advantage of saving network bandwidth, high selectivity, flexible data transmission capability and high confidentiality. As the international organization for standardization continuously improve the relevant agreements of multicast technology, such as RFC3376 defined the IGMPv3 agreement, RFC4602 defined PIM-SM multicast routing protocols, Multicast technology has been widely applied to the production and daily application. Multicast technology can greatly reduce network traffic, especially in the case of multi-user overloading data transmission, the center in routing or trunk line of flow decrease geometrically, whose additional overhead is only multicast user management and data flow distribution produced by routing. IGMPv3 agreement mixing with PIM-SM agreement, can make the user choose the receive traffic data in a number of different multicast group different multicast source. It can not only increase select flexibility of user, to a certain extent, but also reduce meaningless data transmission in the network, thus it greatly improve the utilization rate of the line. In particular, when a large number of users demand for the same real-time data used in police, which bring the multicast technology with a more broad application prospects.This paper mainly carries out the research in multicast management agreement IGMPv3 and multicast routing protocol PIM-SM, and put forward suitable for wireless multicast mechanism of police broadband communications. The second chapter firstly introduces the each version and packet format of Internet Group Management Protocol and the definition of each part. Then it analyzes the multicast routing protocols, such as the PIM-DM, PIM-SM, DVMRP, etc. When it comes the dispersed and the rich data sources application scenarios, IGMPv3 cooperates with the PIM- SM multicast routing protocol, can format PIM-SSM agreement, a specific source version-independent multicast routing mechanism, which is very suitable for a certain security requirement of the sparse user and rich source of scenario. By increasing the authentication module, routing traffic restrictions and other measures, the simulation shows that the network has good resistance to aggressive. Finally, aiming at the condition of the mobile user roaming, this paper proposes a pre-registration multicast model. In the process of users’ moving, according to distance between the node and base station communication, SNR, directional factor weighted combination, the base station can send registration information to the current base station, before the user reaches the next station.