Selecting the optimal buffer management for opportunistic networks both in pedestrian and vehicular contexts

Opportunistic networks are a form of mobile ad-hoc networks that exploit users mobility to provide data sharing. Individual nodes store, carry and forward messages using direct communication between devices; no fixed infrastructure of communication is required. The final goal is to reach the totality of the participating users. The efficiency of message diffusion depends on the users' mobility, the transfer time, and the device buffer management. User's mobility determines the number of contacts and their duration while the transfer time depends on the size of the interchanged messages and the channel throughput. The device buffer management is a critical factor since, due to its limited size, the chosen policy for forwarding messages when a connection is available and for message dropping when the buffer is full can impact greatly on the diffusion of the messages. In this paper we focus on this issue, evaluating the impact of different buffer management approaches in two different scenarios: pedestrian and vehicular. The results show that the best buffer management is the combination of smallest message forwarding and largest message dropping. We also show that a TTL (Time to Live) of 24 hours allows the best diffusion because it corresponds to the daily movement pattern of the nodes.