Packet Forwarding Assurance in Delay Tolerant Networks

In conventional TCP/IP networks, there is a differentiated service architecture for providing different levels of services. Similarly in Delay Tolerant Networks (DTNs), we need to provide differentiated services where the network resources are limited, particularly in buffer size. Since DTNs have their own network characteristics, such as multiple copy routings, and intermittently connection, the traditional differentiated service architecture does not apply. In this paper, we propose two simple schemes to provide a packet forwarding assurance in DTNs. The two proposed schemes are an absolute differentiation scheme, and a relative differentiation scheme. These schemes have a prioritization process when a packet is dropped from the local buffer at each node to provide a high priority to Assured Forwarding (AF) packet and a low priority to Best Effort packet. We show that the proposed algorithms can dynamically find the appropriate target delivery ratio for AF packets, which can provide forwarding assurance for AF packets while avoiding starvation of BE packets, without any global information even though network conditions are changing. We believe that our study is the initial step toward exploiting differentiation services in DTNs.