A WSN consists of a large collection of sensor nodes which have limited computational and communicative capability and low power resources. Due to the restricted communication range, WSNs use multi-hop data transmission. Reliable communication is important to achieve a certain level of quality of data communication. However, a big challenge in routing protocols of WSN is to achieve maximal robustness against path failure with minimal energy consumption. Directed diffusion, energy aware routing and rumor routing, low-energy adaptive clustering hierarchy are popularly used for routing in WSNs.