This paper presents a framework for evaluating routing algorithms in Delay Tolerant Networks (DTNs), where messages are transmitted across a time-varying connectivity graph with limited buffer capacity and no guaranteed end-to-end path. The authors propose a set of routing algorithms and compare their performance based on the amount of knowledge they require about the network topology. They find that algorithms with limited knowledge perform poorly, but efficient routing strategies can be developed with minimal additional knowledge. The paper also introduces a linear programming formulation for optimal routing and discusses various routing approaches, including proactive and reactive routing, source routing versus per-hop routing, and message splitting. The authors evaluate the performance of these algorithms using simulations in a scenario involving a remote village connected to a city through multiple communication channels. The results show that routing in DTNs is a complex problem that requires careful consideration of network dynamics, buffer constraints, and message delivery requirements. The paper concludes with a discussion of future research directions in DTN routing.This paper presents a framework for evaluating routing algorithms in Delay Tolerant Networks (DTNs), where messages are transmitted across a time-varying connectivity graph with limited buffer capacity and no guaranteed end-to-end path. The authors propose a set of routing algorithms and compare their performance based on the amount of knowledge they require about the network topology. They find that algorithms with limited knowledge perform poorly, but efficient routing strategies can be developed with minimal additional knowledge. The paper also introduces a linear programming formulation for optimal routing and discusses various routing approaches, including proactive and reactive routing, source routing versus per-hop routing, and message splitting. The authors evaluate the performance of these algorithms using simulations in a scenario involving a remote village connected to a city through multiple communication channels. The results show that routing in DTNs is a complex problem that requires careful consideration of network dynamics, buffer constraints, and message delivery requirements. The paper concludes with a discussion of future research directions in DTN routing.