Delay tolerant networks are a class of ad hoc networks that enable data delivery even in the absence of end-to-end connectivity between nodes, which is the basic assumption for routing in ad hoc networks. Nodes in these networks work on store-carry and forward paradigm. In addition, such networks make use of message replication as a strategy to increase the possibility of messages reaching their destination. As contact opportunities are usually of short duration, it is important to prioritize scheduling of messages. Message replication may also lead to buffer congestion. Hence, buffer management is an important issue that greatly affects the performance of routing protocols in delay tolerant networks. In this paper, Spray and Wait routing protocol, which is a popular controlled replication-based protocol for delay tolerant networks, has been enhanced using a new fuzzy-based buffer management strategy Enhanced Fuzzy Spray and Wait Routing, with the aim to achieve increased delivery ratio and reduced overhead ratio. It aggregates three important message properties namely number of replicas of a message, its size, and remaining time-to-live, using fuzzy logic to determine the message priority, which denotes its importance with respect to other messages stored in a node's buffer. It then intelligently selects messages to schedule when a contact opportunity occurs. Because determination of number of replicas of a message in the network is a difficult task, a new method for estimation of the same has been proposed. Simulation results show improved performance of enhanced fuzzy spray and wait routing in terms of delivery ratio and resource consumption. many real life applications such as mobile sensor networks for wildlife tracking, interplanetary communications, underwater networks, pocket switched networks, and vehicular ad hoc networks (VANETs). [5]. These networks use a bundle layer, which is an overlay protocol lying between application layer and transport layer [5]. Bundles are arbitrary size messages consisting of multiple application packets, which are forwarded in store-carry and forward manner.Conventional ad hoc routing protocols fail to work in such environments as they lack continuous end-to-end connectivity between nodes because of frequent link disruptions. Therefore, such networks make use of store-carry-forward strategy to transfer messages between the nodes, that is, the nodes buffer the messages and transfer it when a contact opportunity arises, and this process is repeated until the message eventually reaches its destination. Similarly, a carry and forward scheme is used in VANETs [6]. This is also somewhat similar to the problem of data dissemination in wireless networks, which has been recently studied in [7], where the main objective is to spread a particular content in a network while guaranteeing a low completion time and also minimizing resource consumption. However, the delays between node meetings in DTNs may be very long varying from hours, days to years, and hence nodes must be capable of s...
