Study On Congestion Control In Delay Tolerant Networks

Delay tolerant network (DTN) is a new type of overlay networking architecture which is based on an abstraction of message switching. The Characteristics of the network and Custody Transfer protocol adopted can easily lead to DTN congestion caused by storage resource exhausted. The network congestion is a great factor to affect the network quality of service, so how to avoid congestion and implement congestion control effectively is a key technology of delay tolerant network.The thesis analyzes the characteristics and the architecture of DTN, and discusses the problems of congestion control in DTN. Deeply studying the congestion control mechanisms based on message migration, then the thesis proposes an improved congestion control algorithm based on class of services. The main research work includes:1. Analyzing the characteristics of DTN, and comparing it with the traditional internet architecture, then contrast the transfer performance with and without custody transfer by simulating, and analyze the advantages of custody transfer applied to DTN. Show the cause leading to DTN congestion and the consequences it brings about, while analyze the characteristics of DTN which influence on congestion control.2. Exploring the issues of traditional end-to-end congestion control mechanisms applied to DTN, considering the feature of Custody Transfer, deeply discussing the congestion control mechanisms based on message migration. When congestion appears at a DTN node, the node migrates the message in the queue to other node to avoid network congestion , and retrieves the message that have been previously migrated when recovered from congestion. The simulation analysis shows that the congestion control algorithm significantly improves the message delivery ratio and system performance.3. Considering the class of services of the message and the problem of push-pull congestion control algorithm, this thesis improved it for improving the transfer performance of the services with high priority, this paper proposes the congestion control algorithm based on class of services, and comparing it with the former. The result show that the algorithm improved is better for improving the transfer performance of the services with high priority. The studies of the thesis indicate that application of congestion control based on message migration could improve the message delivery ratio and enhance the performance of DTN. The improved algorithm based on class of services could improve Quality of Service with high priority.