Distinguishing social contacts and pass-by contacts in DTN routing

The heterogeneity of the application data size needs to be considered in Delay Tolerant Networks (DTN) routing. Depending on the size of data, certain node contacts may not be long enough for complete data forwarding, i.e., data forwarding may be interrupted if the link is disconnected before the completion of data transfer. In this paper, we present a peer-to-peer DTN routing scheme that considers data size and contact duration. We classify node contacts into social contacts and pass-by contacts. The former corresponds to the case social interaction between users is involved, while the latter corresponds to the case contact occurs only due to physical proximity between nodes. Our scheme is novel in the following aspects. Firstly, we utilize both types of contacts unlike the existing social DTN routing which utilizes only social contacts. Large data is forwarded at social contacts which generally has long contact duration. Pass-by contacts are used for forwarding small data. Secondly, we characterize the strength of social ties by combining heterogeneous properties of contacts. We have evaluated the effectiveness of the proposed scheme by simulating the real world contact traces. It is shown that our scheme substantially higher delivery ratio and lower relaying overhead than the existing schemes when the size of data varies.