On the Energy Efficiency and Performance of Delay- Tolerant Routing Protocols Md. Khalid Mahbub Khan 1 , Sujan Chandra Roy 2 , Muhammad Sajjadur Rahim 2[0000- 0002-0014-5125] , and Abu Zafor Md. Touhidul Islam 1 1 Department of Electrical and Electronic Engineering, University of Rajshahi, Rajshahi-6205, Bangladesh 2 Department of Information and Communication Engineering, University of Rajshahi, Rajshahi-6205, Bangladesh khalidmahbub.khan@yahoo.com, sujan.007.ice@gmail.com, {sajid_ice,touhid.eee}@ru.ac.bd Abstract. Delay-Tolerant Network (DTN) is a resource-bound networking sys- tem which consists of many intermittently connected, movable devices known as nodes. Energy can be considered as an important resource for DTN scenarios since these nodes have limited energy. In order to perfect network enforcement, it is necessary to exploit the energy of the nodes efficiently. In DTN, most of the node energy is consumed because of mobility, scanning neighbors to deliver message and message transmission. Node energy has a significant role for suc- cessful transmission of messages. Higher energy of a node means that it has a high possibility to route its message with success across the network. So, for ef- fective message routing it is mandatory to select an energy efficient routing mechanism in DTN environment. This point makes us interested to study the consumption of node energy in DTN scenarios. Within this research, the study of energy issue is focused for DTN routing approaches: Epidemic, Resource Al- location Protocol for Intentional DTN (RAPID), MaxProp, Probabilistic Rout- ing Protocol using History of Encounters and Transitivity (PRoPHET), Spray and Wait, and Spray and Focus with their comparative performance analysis on behalf of four performance criteria: average remaining energy of node, delivery ratio, average latency, and transmission cost. Simulations are performed in Op- portunistic Network Environment (ONE) simulator by varying node density while keeping message Time-To-Live (TTL) fixed and further, message TTL is changed while node density is kept fixed. We have found that Spray and Wait is the most energy efficient DTN routing scheme, whereas Spray and Focus yields the best performance in terms of delivery ratio, average latency and transmis- sion cost. Keywords: Delay-Tolerant Network, Routing protocol, Energy efficiency, Per- formance evaluation, Opportunistic Network Environment (ONE) simulator.