In most of the wireless applications, e.g. military networks, vehicular ad-hoc networks, wild life tracking and sensor network, it is impossible to sustain a complete end-to-end data transmission path from source to destination. Thus, the traditional routing strategies (TCP/IP) cannot work with such environments as they need to establish the uninterrupted path before transmission. The disruption-tolerant network (DTNs) has emerged as technology that enables the communication in highly disrupted environments by intermittently connected mobile nodes. The DTN transmission model follows a store carry and forward mechanism wherein the nodes stores the incoming message , carries it while moving and forward when comes in the transmission range of other contacts. The DTN protocol can be divided as single copy and multi copy. In single copy protocol the node is allowed to generate the unique copy of message and forward it on a unique path. The multi copy protocols generate and transmit the multiple copies of each message and forward it along various paths.
In DTN environment, the communication opportunity exists for short duration and a node cannot transmit all copies of its carried message from its forwarding queue. Hence the order at which the messages are forwarded becomes very important. In this paper, we have proposed a message forwarding order for multi copy Spary&wait routing protocol called as smallest message first. Through simulations, we proved that proposed policy out perform as compared to existing FIFO in context of delivery probability, overhead, latency average and buffer time average.