Node location dependent remaining-TTL message scheduling in DTNs

Delay and disruption tolerant networks (DTNs) adopt the store-carry-and-forward paradigm. Each node stores messages in buffer storage and waits for either an appropriate forwarding opportunity or the message's expiration time, i.e., its time-to-live (TTL). There are two key issues that influence the performance of DTN routing: (1) the forwarding policy that determines whether a message should be forwarded to an encountered node and (2) the buffer management policy that determines which message should be sent from the queue in first (i.e., message scheduling) and which message should be dropped when the buffer storage is full. In this paper, we propose a DTN routing protocol to fit well with the considered island scenario in which a source node and a destination node are located at different islands connected by a ferry. Our proposal integrates three features: (1) binary spray; (2) hop-distance-based forwarding; and (3) remaining TTL consideration for message scheduling based on global knowledge regarding the network. We also evaluate our proposed protocol by comparing it with other popular protocols, namely Epidemic as a baseline and PRoPHETv2 that performs well according to our previous study regarding the island scenario. Our simulation results show that our protocol is able to outperform the other routing protocols, drastically reducing overhead and, at the same time, significantly increasing the total size (amount) of delivered messages. Further, comparative results between features (1) and (2) only and our full proposal (i.e., features (1), (2), and (3)) suggest that remaining TTL consideration has a positive impact on performance.