# Priority-Based Content Delivery in the Internet of Vehicles through Named Data Networking +
Typically, a defer time is calculated before each packet forwarding so that, if the same packet is overheard, then forwarding is canceled for the delayed packet. Two main open issues still exist in the design of vehicular NDN forwarding. First, IoV applications may exhibit very different (and stringent) demands, especially in terms of freshness and latency. For instance, traffic congestion information is \"transient\" and needs to be promptly retrieved, while file sharing applications are characterized by static contents and tolerate longer delays. So far, however, the content type of vehicular applications has not been considered as an input to the NDN forwarding strategy: all vehicles apply the same forwarding rules to all NDN packets. Second, less attention has been devoted to the selection of the best interface(s) where to forward packets, nonetheless the multihome nature of recently manufactured vehicular devices [7; 12]. For instance, in [12], a naive approach is followed of forwarding each Interest to all of the interfaces that are available at the time, i.e., IEEE 802.11 in ad hoc mode for short-range vehicle-to-vehicle interactions, 3G and Wi-Fi mesh networks for long-range communications. In this paper, we aim to take a step forward by designing a comprehensive NDN framework for prioritized content delivery in IoV, we refer to it as \"prioritized NDN\" (pNDN). Our proposal targets the support of data traffic originated by non-safety applications. Indeed, many efforts, both from standardization bodies and academia, have been already devoted to prioritizing the delivery of safety applications through solutions enforced at different layers of the protocol stack, whereas non-safety applications have received a lower interest. The main contributions of pNDN can be summarized as follows:  
* It identifies the content priority with well-known name prefixes and uses the \"freshness\" parameter carried out in NDN packets to further characterize the content delivery demands. * It dynamically holds the NDN forwarding decisions according to the name prefix of contents, by selecting the outgoing interface(s) and properly tuning the defer timers of broadcast transmissions over the 802.11 OCB interface. The performance of pNDN has been evaluated in a realistic fashion by leveraging the official NDN simulation framework and compared with reference NDN implementations without traffic prioritization. Results show that pNDN outperforms benchmarking schemes in that it speeds up the delivery of high-priority packets, while also reducing the latency of low-priority traffic, at the expenses of a slightly higher overhead. The remainder of the paper is organized as follows. Section 2 debates the motivations for our work; background material about NDN and its usage in vehicular environments is provided in Section 3. The description of the proposed NDN solution is reported in Section 4. Simulation settings and tools are described in Section 5. A performance evaluation against legacy NDN implementations is presented in Section 6. Conclusions and hints for future works are provided in Section 7.