Intermittently connected mobile networks are wirelessnetworks where most of the time there does not exist a completepath from the source to the destination. There are many real networksthat follow this model, for example, wildlife tracking sensornetworks, military networks, vehicular ad hoc networks, etc. Inthis context, conventional routing schemes fail, because they try toestablish complete end-to-end paths, before any data is sent.To deal with such networks researchers have suggested to useflooding-based routing schemes. While flooding-based schemeshave a high probability of delivery, they waste a lot of energyand suffer from severe contention which can significantly degradetheir performance. Furthermore, proposed efforts to reduce theoverhead of flooding-based schemes have often been plaguedby large delays. With this in mind, we introduce a new familyof routing schemes that “spray” a few message copies into thenetwork, and then route each copy independently towards thedestination. We show that, if carefully designed, spray routing not only performs significantly fewer transmissions per message,but also has lower average delivery delays than existing schemes;furthermore, it is highly scalable and retains good performanceunder a large range of scenarios.Finally, we use our theoretical framework proposed in our 2004paper to analyze the performance of spray routing.We also use thistheory to show how to choose the number of copies to be sprayedand how to optimally distribute these copies to relays. Efficient Routing In Intermittently Connected Mobile Networks The Multiple Copy Case
Under low load, Spray and Wait results in much fewer transmissions and comparable or smaller delays than flooding-based schemes.
Under high load, it yields significantly better delays and fewer transmissions than flooding-based schemes