Evaluation of Spray Based Routing Approaches in Delay Tolerant Networks

Delay Tolerant Networks (DTN) are mobile ad-hoc networks in which connections are often disruptive or discontinuous. Data forwarding using an appropriate routing strategy is a highly confronting issue in such networks. The traditional ad-hoc routing protocols which require end-to-end connectivity fail to function here due to frequent occurrences of network partitions. Spray and Wait (SaW) routing algorithm is a popular controlled replication based DTN protocol which provides a better delivery performance balancing the average delay and overhead ratio. An empirical analysis of various spray based approaches that have been proposed for DTN has been performed in this paper to compare and evaluate the basic Spray and Wait algorithms (Source Spray and Wait and Binary Spray and Wait) with some of its major improvements (Spray and Focus, Average Delivery Probability Binary Spray and Wait and Composite methods to improve Spray and Wait). The main aim of this comparative study is to verify the effect of utility metrics in spray based routing protocols over simple spray based approaches. The ONE simulator has been used to provide a simulation environment to evaluate these algorithms and generate results. The performance metrics used are delivery ratio (DR), overhead ratio (OR) and average latency (ALat). The simulation results show that in terms of delivery ratio and average latency, Composite methods to improve Spray and Wait which incorporates delivery predictability metric in the wait phase and also acknowledgements to delete already delivered messages from a node’s buffer, outperforms all the other variants compared.