A Design And Realization Of Multicast Fast-forwarding System Based On Linux

With the development of broadband multimedia network,various broadband network applications emerge endlessly,such as network audio application,network video application,data and information distribution and multimedia remote education.These broadband network applications provide the challenge to the carrying capacity of current broadband multimedia.For the network bandwidth and service quality,some problems exist such as network delay and data loss.Currently the network capacity can't meet the need of the multimedia applications.By using multicast technique,the above problems can be solved.Even the number of user increases several times over,there is no need to increase the bandwidth of backbone network.Then,the bandwidth of backbone network consumed by thousands of multicast application users and one multicast application user consume is the same.It can meet the need of broadband application to the bandwidth and network service quality.The multicast forwarding of network equipment can enhance the efficiency of information transfer and decrease the consumed bandwidth of information transfer.The dissertation explores the multicast forward technique combining with a development of rapid forwarding project.Based on the research of some relative techniques such as the principle of multicast technique,multicast route protocol,forwarding mode,interrupt and synchronization mechanism of Linux,It analyzes the transfer mode and the characteristics of datagram and gives the rapid forwarding mechanism.The forwarding mechanism combines the thought of 'forwarding once,exchanging many times'.For every data stream,it needs to retrieve the forwarding table only once.Using the rapid forwarding mechanism in the multicast forwarding workflow,the network layer compression can be realized.So it can not only reduce the queue information process and much more repetitive top layer business process,but also can save the multicast forwarding time of datagram in network equipment.At the same time,according to the characteristics of multicast addressing,this dissertation adopts four-layer Hash construction to organize and save the multicast forwarding table.For every searching table process we can achieve the result by four comparisons at best.So we can get the faster speed.The multicast forwarding executed in the soft interrupt guarantees the timely forwarding process and effectively utilizes the multi-kernel synchronization process capacity of Linux.The combination mode of RCU mechanism with spin lock protects the share table resource in kernel space,saves the consumption of lock and further optimizes the multicast forwarding capacity.Finally,the function and capacity test of rapid multicast forwarding system proves that the rapid forwarding mechanism researched by this dissertation can make the network equipment effectively and stably forward the multicast datagram and reinforces the multicast forwarding capacity under the circumstance of many business coexisting.The mechanism enhances the unitary forwarding efficiency of network equipment and realizes the effective and reliable multicast communication.