# All about Delay-Tolerant Networking (DTN) Contributions to Future Internet
## 4 Discussion and Conclusions  
We have highlighted the potential of DTN to contribute to a variety of internet applications and also to contribute toward extending the internet in order to accommodate isolated environments such as underwater or space. The key characteristics of this technology that enable a unification of diverse environments are the custody transfer and the storage capabilities. In fact, the way DTN operates is not in contrast with the traditional end-to-end architecture of transport protocols; it transforms it into an end-to-end architecture with one sliding end. Indeed, the custody is gradually transferred to the next node each time, thereby making graduated progress toward reaching the other end. This new philosophy of communication, even when connection gaps exist, allows for a new perspective for interconnecting devices: Not all devices need to be interconnected at all times. Hence, information can be shared from devices that may be interconnected in the near future. Such devices and their users can now become active members of the internet community even when they are temporarily disconnected. \begin{table}
\begin{tabular}{c c c} \hline \hline
**Challenges** & **Papers** & **Focus** & **Solution/Protocol** \\ \hline \multirow{8}{*}{\
\begin{tabular}{c} Propagation delay, \\ multivariate attenuation, \\ limited bandwidth, \\ high transmission power, \\ bit error rate, \\ intermittent connectivity, \\ no position information, \\ limited energy demands \\ \end{tabular} } & \multirow{8}{*}{
\begin{tabular}{c} Proptech and epidemic routing \\ UDTN-RS \\ \end{tabular} } \\  & & \\ \cline{1-1}  & & \\ \cline{1-1}  & & \\ \cline{1-1}  & & \\ \cline{1-1}  & & \\ \cline{1-1}  & & \\ \cline{1-1}  & & \\ \cline{1-1}  & & \\ \cline{1-1}  & & \\ \cline{1-1}  & & \\ \cline{1-1}  & & \\ \cline{1-1}  & & \\ \cline{1-1}  & & \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Summary of underwater-related literature works. Focusing on the specified domains presented in Section 3, i.e., space, ICN and NDN, IoT and smart cities, and underwater, we have described a number of works that utilize DTN within each domain. In space, DTN allows for interconnecting space devices and permits an alternative solution to line-of-sight limitations, thus allowing for a 24/7 paradigm and opening a new era for satellite technologies as well. In particular, we have identified the necessity--and, in turn, the challenges--to implement and evaluate the proposed DTN-based solutions (e.g., protocols, algorithms, or frameworks) not only in simulated environments but also on a large scale, as well as in real-world scenarios. Along these lines, scalable testbeds such as DEN or SPICE have emerged, thus providing space-related environments for the evaluation of solutions, with some proposing integration with cloud-based computing and containerization technologies. Furthermore, satellites have gained increased attention as significant enablers in the new era of the internet and communications, thereby aiming to harvest the close-to-terrestrial delays that LEO satellite communications provide. This has implications for a range of terrestrial domains such as internet services, Earth observation, energy, maritime, agriculture, and military applications. However, some of the related challenges, protocols, and solutions they aim to solve include the routing and scheduling of data transmission in intermittently connected networks; efficient resource allocation to optimize bandwidth utilization; seamless integration and interoperability with existing terrestrial networks, technologies, and protocols; and robust security mechanisms. Also, it is worth noting that the incorporation of DTN protocols in ICN architectures allows for a publish/subscribe model even when users are temporarily disconnected but still gather useful information from their local spot. This information can be shared or delivered to the interested users if they do not demand immediate answers to their queries.