TTL based routing in opportunistic networks

One of the major problem in routing messages in an Opportunistic Network (OpNet) is the absence of a complete end-to-end path from the source to the destination. To deal with such adversity many routing protocols employ epidemic techniques to flood the network with multiple copies of a message. Although flooding many copies of a message in the network increases the chance of the message delivery, it can lead to a very high network overhead and can cause network congestion. On the other hand, the quota based routing protocols restrict the maximum number of copies of a message in the network by setting a replication factor. Such protocols maintain comparatively low overhead but suffer from low delivery ratio. In this paper, we introduce a novel quota based routing protocol, TTL Based Routing (TBR). TBR prioritizes both the schedule of messages to be forwarded to the neighbor and the schedule of messages to be dropped from the buffer. These priorities are based on massage time to live (TTL), message hop count, message replication count and message size. The TTL based message priority enhances the chance of message delivery by giving preference to the messages having the earliest deadline. Our simulation results show that, TBR achieves more than 10-15% higher delivery ratio than that of the available quota based routing protocols while incurring 10% to 15% less overhead. TBR not only matches the delivery ratio of flooding based routing protocols but also achieves better delivery ratio with 70% to 75% less overhead.