A Structured Review of Time‐Centric Approaches in Delay‐Tolerant Network Routing: Categorization, Comparative Evaluation, and Insights

ABSTRACT Recently, the fact that networks are always changing has made it more important for network applications to be able to connect with peers in a variety of situations, like when networks are unreliable, nodes move around a lot, or resources are limited. Delay tolerant networks (DTNs) provide the solutions to scenarios where disconnection is frequent and delay is high. In this type of network, predicting an appropriate relay node is a challenging task. To deal with these challenges, DTNs leverage various utility metrics such as frequency of contact, encounter history, or duration of contact. In such a challenging environment, time‐centric approaches provide an effective solution for optimal relay node selection. These routing protocols use contact duration, encounter frequency, intercontact time, and so forth, metrics for relay node prediction. This study critically examines the time‐centric approaches in delay‐tolerant network routing. The paper divided existing protocols into four different categories for spray strategies, next‐hop prediction, shortest path estimation, and hybrid and other techniques. To provide a structured review, this paper begins with the general discussion of routing protocols that employ time‐centric measures and then dives in depth, covering various aspects. By providing a comparative analysis of key algorithms, this paper covers a structured review of resource consumption, technology used, and performance of different routing protocols with different parameters. This paper also discusses open research issues and intends to motivate new research and development in this area.