## 6 Results
### DTN Routing
Infrastructure-based protocols use location information of nodes like routes or the distance between nodes: route or map-based, e.g., world model-based and MF; distance-based, e.g., MOVE (movement of vehicle) uses the movement direction of nodes, and DAER (Direction Aware Epidemic Routing) uses the distance from the destination to evaluate the utility metric. Hybrid and others use more than one type of information to make decisions, e.g., PER (Predict and Relay), SimBet, and CAR [23]. The CNS algorithm uses the Markov model to predict the location of nodes, so there is a higher delivery probability. Because the algorithm uses contact history, the overhead will increase as the network grows. Comparing CNS with Epidemic, Spray and Wait, and Prophet for the scenario established, CNS had a better delivery ratio and less delay [28]. Chenji and Stoleru describe two main routing protocols for emergencies. Intercontact routing uses the recurrence of node movement to define delivery routes and Raven (Risk AversE routing in dtNs), which picks routes where jitter is lower. They also suggest that intercontact routing consumes less energy while keeping higher delivery rates by reducing the number of transmitted messages [31]. Hybrid MANET-DTN combines routing approaches. Whereas MANET assumes an available end-to-end path between the source and destination, in DTN, there is no end-to-end connection; therefore, many copies might be stored and forwarded. In MANET, when there is no end-to-end path, nodes might resend packets if they have not received an ACK [32]. Hybrid MANET-DTN routing protocols are categorized in DTN mechanisms inserted in MANET routing schemes, combining the DTN Bundle Protocol with MANET routing, and from scratch routing protocols for diverse networks [33]. The Hybrid DTN Routing Protocol (HDRP) combines flooding and forwarding mechanisms to find a balance and improve delivery rates. It is designed for IoT, drones (UAVs), and smart grid scenarios [34]. Prophet BSAS is a redesign of Prophet that allows for the transmission of higher amounts of data and reduces useless connections, based on a utility function that takes into consideration the transmission capacity, forwarding success rate, and the storage space of the nodes [35]. Context-aware adaptive routing (CAR) solves the problems of intermittent connectivity by estimating the next hop based on the prediction techniques of the Kalman Filter Algorithm and the utility function. It does not require nodes to keep track and store information on the history of encounters, which makes it suitable for networks with limited resources, such as CubeSat networks. Moreover, QoS techniques, including load balancing, dropping policies, and link recovery are suggested to enhance routing performance in such scenarios [5]. Wang simulates DTN time-space routing schemes, including Time-Expanded Graph (TEG) and Contact Graph Routing (CGR) [36]. Verma performs a simulation on The One comparing Epidemic, SNW, Prophet, EBR, CDBR (Contact Duration Based Routing), and ICR routing protocols. In smaller networks with fewer nodes, all give a comparable performance [23]. * Number of nodes. With the higher number of nodes, (>60), SNW, Prophet, and ICR show comparable performance and outperform the others. Epidemic, Prophet, and CDBR suffer from high overhead because they rely on multiple copies of messages. * Buffer size. SNW, ICR, and CDBR are affected by an increased buffer size. ICR and SNW are good performers with high delivery ratios and low overheads. * Message size. For larger-size messages, all algorithms have low performance, but for smaller sizes, SNW and ICR outperform the others. Design. Three limitations that should be taken into consideration when designing DTN routing protocols include disconnection that results from mobility and energy constraints, high latency, which varies from hours to days, and resource scarcity, which can affect store-and-forward features [27].