Abstract
Designing a good routing protocol for an opportunistic network is difficult because of its inherent characteristics (Lack of context information, heterogeneity, storage constraints, unstable connectivity, etc.). Due to the aforementioned constraints, most nodes flood messages in the network. This is done with the assumption that the message will eventually reach its final destination than continuously keeping it in the nodes’ buffer. As such, flooding-based schemes are used. These flooding based schemes have the disadvantage of causing network congestion, over utilization of system resources, as well as causing network overhead. If these schemes are not properly managed, packets would be lost and drop in network performance would be recorded. This research is aimed at improving the performance of the epidemic routing (a flooding-base routing protocol) by managing congestion. Buffer size advertisement congestion control strategy was used. Simulation was carried out using the opportunistic network environment (ONE) simulator which the codes are written in java. The buffer size advertisement congestion control strategy was developed and incorporated on the epidemic routing protocol on the Helsinki benchmark simulation area. Results were obtained and compared with the epidemic routing protocol. The epidemic routing protocol with buffer size advertisement congestion control strategy was seen to have outperformed the epidemic routing protocol without congestion control strategy by 25% in terms or delivery probability. In terms of packet loss, the buffer size advertisement congestion control strategy outperformed the epidemic routing protocol by 44%. These results showed that proper management of congestion can greatly improve the performance of opportunistic network.

Key words: Opportunistic network, congestion, flooding-based routing, buffer management