## 5 Conclusions  
In this paper, we review dynamic forwarding, caching, security, naming, and wireless communication aspects of named data networking for vehicle-to-everything communication. Our contribution to the field is the identification of future challenges and opportunities in these sub-fields. We found that NDN, as a technology, is promising, as it features inherent security concepts, dynamic packet forwarding, and inherent caching. Achieving the aforementioned features with IP requires tremendous effort.  
For dynamic forwarding in NDN, we found that there is unexploited potential in the Interest packet format, as the ForwardingHint is not leveraged by current forwarding strategies. Furthermore we identified the problem of forwarding unsolicited data which arises through node mobility. Currently, this case would require retransmissions of Interests and consequently increase the delay. Additionally, we found that many forwarding strategies are impractical for a mobile scenario, as they require a priori routing information or knowledge of the overall network topology. Eventually, the question of how to prevent broadcast storms caused by Interest flooding remains.  
The aspect of content caching is well researched in current literature. While most of them approach the problem of vehicle mobility, data category is not taken into account. With driving assistance systems and autonomously driving vehicles, there will be data vital for traffic safety which has to be cached differently than conventional data, e.g., a video stream.  
From the point of view of vehicle-to-everything communication, NDN inherently covers security and authenticity. Security currently comes at the cost of bad cache hit ratio. Considering authenticity, there is no feasible solution against content poisoning attacks. Data integrity, as well as byzantine vehicles are not extensively covered in current literature. We argued that simulation of V2X use cases is essential for progress in the field. Therefore, we characterized V2X scenarios and discussed simulation of NDN transport. We found that in ns-3, at a fixed delay model, the choice of channel model has a high impact on the delay. We therefore emphasize that one has to be careful to choose the appropriate channel and delay model for the current simulation.  
We end this work with a summary of possible research questions for future work:  
* How to deal with unsolicited data in V2X context?
* How to incorporate vehicular mobility (vehicles entering/leaving communication range) in the forwarding process?
* How to make use of the NDN ForwardingHint?
* How to prevent broadcast storms originating in Interest flooding?
* What should a caching strategy for multiple types of data look like?
* How to combine geo-location and popularity information in content caching?
* How to deal with caching, encrypted content, and the lack of computational resources?
* How to deal with content poisoning attacks without verification at intermediate routers?
* How to detect and deal with byzantine vehicles?
* How well do models of the physical channel map the uses cases we want to simulate?  
**Author Contributions:** Both authors have the same contribution to this paper.  
**Funding:** The authors would like to thank the Austrian Institute of Technology, where this work has been partly funded by REALISM (FFG project grant no. 864188).  
**Conflicts of Interest:** The authors declare no conflict of Interest.