What is the basic difference between spray and wait routing protocol and other routing protocols? And what is the main benefit of using the spray and wait protocol?
Most network routing protocols are designed for use in fairly stable networks where paths can be known, but they have the ability to change dynamically as the network changes. These protocols are deterministic, and they are optimized for the accurate, speedy delivery of network traffic.
The Spray and Wait algorithm is designed to work where paths may be unknown and may frequently change. These networks are tolerant of delay in delivery of traffic.
The abstract for Spray and Wait describes it pretty well:
Intermittently connected mobile networks are sparse wireless networks where most of the time there does not exist a complete path from the source to the destination. These networks fall into the general category of Delay Tolerant Networks. There are many real networks that follow this paradigm, for example, wildlife tracking sensor networks, military networks, inter-planetary networks, etc. In this context, conventional routing schemes would fail.To deal with such networks researchers have suggested to use flooding-based routing schemes. While flooding-based schemes have a high probability of delivery, they waste a lot of energy and suffer from severe contention, which can significantly degrade their performance. Furthermore, proposed efforts to significantly reduce the overhead of flooding-based schemes have often be plagued by large delays. With this in mind, we introduce a new routing scheme, called Spray and Wait, that "sprays" a number of copies into the network, and then "waits" till one of these nodes meets the destination.Using theory and simulations we show that Spray and Wait outperforms all existing schemes with respect to both average message delivery delay and number of transmissions per message delivered; its overall performance is close to the optimal scheme. Furthermore, it is highly scalable retaining good performance under a large range of scenarios, unlike other schemes. Finally, it is simple to implement and to optimize in order to achieve given performance goals in practice.