Research On Construct, Maintenance And Forwarding Policy Of Minimum Delay Tree For Application Level Multicast

Researchers propose Application Level Multicast because IP Multicast is hard todeploy. Application Level Multicast provides multicast services in the application levelby implementing multicasts function on the host computers, while forward data by IPUnicast in physics network. Because thefinite process capabilityand bandwidth of hostcomputers, replication and forwarding dissipate much time and result in high delay inmulticast. Contemporary, the host computers tend to validate or drop out from themulticast group result in split of the multicast tree. This will influence the downstreamnodes receive the data from the multicast resource. This paper mainly research theconstruction and maintenance of multicast tree with minimumdelayand the forwardingpolicy of the multicast nodes in order to resolve the problem of the high delay anddisruptionofApplicationLevelMulticast.Themaincontentsandfruitsofthispaperareoutlinedasfollows:Firstly, this paper analysis the factors that affect the delay of application levelmulticast which includes the delay of the communication link, degree and forwardcapabilityof nodes.A new model named as DNMD is presented byimprove the DCMDmodel because it doesn't take the diversity of node forward capability into account.Then GA is used to resolve DNMD model in succession. The validity of the algorithmandrationalityofthemodelisprovedbysimulation.Secondly, the dynamic maintenance of multicast tree includes recovery of thedisrupted tree and the new join nodes process has been studied in this paper. A mixedrecovery policy is proposed by take the advantage of ROT algorithm. According to thedifferenceofnodestate,diefferentpolicyisusedtorecoverthemulticasttreeinordertooptimize the delay.Aiming at the new node join problem, an algorithm is proposed tofind minimumdelayfromthenewnodetotherootisobject.Lastly, this paper propose a forwarding policy of multicast nodes to optimize thedelay of a constructed multicast tree by arrange a proper order when a node forwarddata to it's children nodes and prove that the delay of multicast tree is optimum if thenon-leaf nodes forward data according to the proposed policy by reasoning. Then anexample is used to illustrate how to use the policy. The validityof the policy isprovedbysimulationthatcarriedoutinMATLAB.