Abstract Wireless sensor networks (WSN) are a recent class of distributed systems that consist of sensors. These sensors are essential in monitoring environmental or physical states, like temperature, sound, movement, vibration, or pollutants. As compared to most computers, which primarily rely on data supplied by users, sensor networks take into consideration the surrounding environment. This new concept has given rise to many new protocols that are specially designed for WSN, in which energy effects are considered. Consequently, much attention is given to routing protocols because they tend to be different depending on the network and application design. This paper analyses the various routing protocols for sensor networks and gives a categorization for the different methods pursued. Thus, the three main classes of routing protocols discussed in this research are data-centric, hierarchical, and location-based. Every routing protocol is evaluated under the necessary category. The research concludes with a general comparison and discussion of research issues. Introduction The growth of wireless sensor networks has motivated many researchers to take the advantage of sensor opportunities. WSN is now used in several industrial applications, such as process monitoring, machine health monitoring, and traffic control (Ramesh et al. 2006). In sensor networks, micro-sensors are normally developed with information processing and communication abilities. The sensing route determines the light that surrounds the sensor environment and transmits the ambient into electric signals. Transforming such signals enables the network system to know the characteristics of the objects or events occurring in the environment. The sensor then sends the collected information to the sink (command center) through a transmitter. The reduced cost and size of sensors due to technological innovations has increased the interest of researchers in expanding the use of unattended sensors. This has motivated serious research in recent years addressing the possibility of cooperation among sensors in processing data and the management of the sensing events and flow of information to the sink. A normal structural design for such shared distributed sensors is a network designed in an ad hoc manner, consisting of wireless links. Networking idle sensor nodes are deemed to have a lot of impact on the reliability of most civil and military applications like safety, surveillance, and disaster administration. These systems work on data collected from different sensors to monitor activities in a specific area. Conversely, sensor nodes are restrained in energy distribution and bandwidth. Such limitations combined with a usual operation of many sensor nodes have created many issues in the design and organization of sensor networks. These problems enhance energy consideration at all the networking protocol layers. At the network layer, the main consideration is to find methods of setting up an energy-efficient route and reliable transmission of data from the sensor nodes to the command center so that network survival is sustained (Akkaya & Younis 2003). Moreover, due to many features that differentiate sensor networks from modern communication and wireless ad hoc networks, routing in WSN is very challenging. Firstly, it is difficult to develop a global addres