The Routing Research Concerned On Buffer Occupancy And Forwarding Rate In DTN

The premise of the communication in Internet is that the path is end to end and the link is continued, and the characteristic is that it has small round-trip delay, symmetrical data rate and low error rate. In some poor and restricted communication network environment, the end to end path doesn’t exist and the network doesn’t satisfy the TCP/IP protocol requirements, either. Then, DTN (Delay and Disruption Tolerant Network) make it possible in restricted communication networks, which usually have relatively low delivery ratio, long average delay, large changes in networks structural, and even a bad system performance. DTN enables intermittent network communication to be possible and contributes to the connection for Internet heterogeneous network, which is a new overlay network. Also, DTN application is widely applied to interplanetary networks, military networks, and vehicle networks and so on. It has bright prospects.In DTN, in order to solve the problem that the low delivery ratio in network and the large average delay, DTN has taken multiple copy of the routing strategy, the packet is carried and storied by several nodes, thereby increasing the likelihood of the message being delivered to the sink. In the Spray And Wait(SAW) routing, the number of copies of a node is determined so that it results certain blindness in the number of nodes, then we develop the policy to adjust the number of copies of the packets based on network conditions, it is critical to improve network performance.Although the routing of multiple copies will have higher delivery possibilities than that of single copy, but buffer is easy to overflow. As a result, network congestion is induced and network bandwidth load is increased. Because the epidemic routing will forward packets once opportunity connection happens and the congestion in epidemic routing is particularly significant, it is important to come up with the policy of buffer scheduling in epidemic routing.The research of DTN is based on routing algorithm and buffer scheduling strategy to improve algorithm. Thus the delivery rate is improved and the network delay and cost is reduced. This paper improves the routing algorithm and buffer scheduling policy, the research project is as follows:(1) In SAW routing algorithm of DTN, the number of copies of the message is certain, which resultes in some blindness about the forwarding number of the message. To deal with this issue, it studies the relationship between the final average buffer occupancy of the node and the initial number of copies, and proposes a Spray and Wait Routing Concerned on Buffer Occupancy (SAW-BO) in DTN. The algorithm adjusts the initial number of copies dynamically based on the final average buffer occupancy rate of the node. It ought to increase the initial number of copies to increase the delivery ratio when the final average buffer occupancy of the node is relatively low and it should decrease the initial number of copies when the final average buffer occupancy of the node is relatively high to avoid the occurrence of congestion.(2) The forwarding rate of a node is related to the activity, the buffer size, the network throughput and other features of the node. Higher forwarding rate indicates that the node makes more contributions to the network. This policy has presented a concept named forwarding rate and proposed a buffer scheduling strategy based on it. Considering the message’s life cycle, the buffer scheduling strategy is performed according to the forwarding rate of source node. Messages which have higher forwarding rate of source node are forwarded firstly. Similarly, messages which have lower forwarding rate of source node are discarded firstly.3. In this thesis, the two routing algorithms are simulated to assess and compare the performance of system with the original routing.