# Priority-Based Content Delivery in the Internet of Vehicles through Named Data Networking +
## 3 Background and Motivations  
### Vehicular NDN  
Several ICN architectures for the future Internet have been designed so far [6]; they all support name-based communication and in-network caching, but differ in the implementation details. Among them, Content-Centric Networking (CCN), originally proposed by [PERSON], is under continuous development by research initiatives worldwide, including the CCNx project ([[http://blogs.parc.com/ccnx/](http://blogs.parc.com/ccnx/)]([http://blogs.parc.com/ccnx/](http://blogs.parc.com/ccnx/))) and the Named Data Networking (NDN) project ([[https://named-data.net/](https://named-data.net/)]([https://named-data.net/](https://named-data.net/))).  
The applicability of NDN in vehicular networks has been investigated in recent years [4; 24; 25]. Indeed, NDN receiver-driven connectionless communications, based on the exchange of two packet types--called Interest and Data--and pervasive in-network caching particularly suit the vehicular ecosystem.  
Content retrieval in NDN starts when the consumer node requests a Data packet by broadcasting an Interest, which carries a hierarchical content name. There are no restrictions in the name components and their composition. For instance, in [25], the following scheme has been proposed: /traffic/geolocation/timestamp/data-type/nonce, where the component traffic is the application identifier, the geolocation component identifies road, section and direction, the timestamp component represents a time period, the data type component indicates the meaning of the data itself, e.g., vehicle speed, and finally, the nonce is a random number generated by the publisher.  
Interest and Data processing at each node is performed with the help of three data structures: the Content Store (CS) that caches incoming Data; the Pending Interest Table (PIT) that keeps track of the forwarded Interests and their incoming interface; and the Forwarding Information Base (FIB), used as a routing table to select the outgoing face(s) for incoming Interests. In NDN, the term face is used to indicate the interface over which packets are received or delivered (i.e., network interfaces or application interfaces).  
On the Interest reception, an NDN node \(N\) first looks in its CS for a name matching. If the content is found, it replies with the cached Data. Otherwise, if there is a matching entry in the PIT, \(N\) discards the Interest since a pending request is already outstanding. If not, a new PIT entry is created, and then, an FIB lookup returns the outgoing face(s), if any, where the Interest will be forwarded towards the provider. Data packets are not routed; they simply follow the chain of PIT entries in each crossed node back to the consumer.  
Each intermediate node may cache incoming Data packets, so to serve future requests.  
Although the NDN forwarding fabric coupled with in-network caching can enable simple and effective interactions in IoV, a major open issue is related to the deployment of the strategy layer, which implements the forwarding strategy and decides if, when and where to forward an incoming Interest. In the following, we survey the related literature, by distinguishing the case when only V2V and V2R interactions are enabled over the IEEE 802.11 OCB face (i.e., single-face communication), and the case when also V2I interactions are enabled (i.e., multi-face communication). It is worth noticing, however, that priority-based named data dissemination in IoV is still almost unexplored.