The Congestion Control For DTN Based On Message Redundancy Removal Technology

In DTN network, nodes move frequently and limited of ability, there is noend-to-end path in this network. So the aim of the routing protocols is not to find thebest path, but is to deliver more messages. To achieve this goal, there are so manymessages and duplication in DTN, which could make congestion. So it is importantfor routing protocol to keep balance between the network overhead rate and thenetwork performance.Redundancy removal is an important way to avoid the congestion, which canreduce the number of copies of the message in the network, and can make the nodeshave more cache resources. One hand reducing the message redundancy considers theproducing of the message. On the other hand, it also takes deleting message into count.So it can reduce network overhead rate, at the same time, it also improve the rate ofmessage transmission. Three new effective mechanisms for reducing the messageredundancy are proposed.(1) In order to control the number of the copies of the message in the wholenetwork, at the same time to avoid the node congestion in the part. This paperpresents a new protocol named adaptive controlling the number of the duplicationprotocol. With this protocol, the node can decide the number of the copies of themessage independently, according to the information of the neighbour node cache andmessage size. Experimental results show that, compared to the old PROPHET routing,the proposed protocol can improve the delivered message rate by fifty-six percentage,and reduce the overhead rate by seventy percentage.(2) How to delete unnecessary data timely, this paper proposed two newprotocols, one named setting TTL of data protocol, the other named triggering ACKspontaneously protocol. When the node buffer occupancy rate reaches a certain level,the data will be classified into two parts according to the number of packet forwarding.And set the TTL of the two parts data independently. According to the number andfrequency of the delivered message duplication, the network produces ACKinformation spontaneously. The experimental results show that both mechanisms canremove the invalid duplication quickly, avoid congestion effectively. And whennetwork appears congestion, both mechanisms can relieve congestion quickly.(3) There is not end-to-end reliability link in DTN, so how to transmit ACK appears much more difficult. ACK receipt should be suit for routing algorithm. AnACK receipt protocol called ABR(ACK Based on Routing) is proposed in this paper.And this algorithm is realized on PROPHET. Experimental results show that, theperformance of this new protocol can shorten message delay, and improve thedelivered message.