## 3 Information Centric Networking (ICN)  
Current Internet architecture is a host-centric design based on the TCP/IP protocol which was developed in the 1970s and adopted as the protocol standard for ARPANET (the predecessor of the Internet) in 1983. A great deal of research has been undertaken to address the limitations of TCP/IP networks in terms of scalability, transmission efficiency, mobility, and security.  
ICN is an emerging paradigm for the future Internet that involves a radical change. It allows content access regardless of its location by leveraging forwarding, name-based routing, security, and caching. It is proposed to replace the current TCP/IP architecture offering a flexible network structure in the IoT environment.  
Many ICN architectures have been proposed over recent years [44], including data-oriented network architecture (DONA) [45], content-centric network (CCN) [7] and named-data networking (NDN) [46]. NDN is one of the four NSF FIA projects aimed at designing the future Internet architectures with the objective of completely overhauling the Internet by replacing IP with content chunks as a universal element of transport. Figure 4 shows the comparison between TCP/IP and NDN.  
Traditional IP networks need to carry out two operations. The first is performed in the routing (or control) plane, in which the routers communicate routing updates and select  
Figure 4: Comparison of host-centric and information-centric stack [46].  
the best path for constructing the forwarding information table (FIB). The second operation is performed in the forwarding (or data) plane, and involves following the directives contained in the FIB to perform the forwarding. The routing plane is stateful and can adapt to network changes, including link failure, router crashes, new routes, or alternative better paths. However, the IP forwarding is stateless and cannot adapt to anything without instruction from the routing control plane. This has often been referred to as \"smart routing and dumb forwarding\".  
NDN replaces the IP dumb-forwarding by stateful forwarding. Instead of distributing IP prefixes, the routing protocols distribute the name prefixes. Stateful forwarding is a process that records incoming interest packets in the PIT and uses the recorded information to forward the retrieved data packets back to the consumers(s). The recorded information can also be used to measure data plane performance, e.g., to adjust interest forwarding strategy decisions. All communication in NDN is performed using two distinct types of packets: interest and data. As shown in Figure 5, each NDN router (vehicles, RSU, BS, MBS, etc.) maintains three major data structures: a content store (CS) for temporary caching of received data packets, a pending interest table (PIT), and a forwarding table (FIB) [47].  
Instead of sending packets between a source and destination devices identified by their numeric IP addresses, NDN disseminates named data at the network level, forwarding names directly that carry application semantics. Moreover, each packet in NDN is secured at the time of production, allowing data replication anywhere in the network and preserving the security properties of the data over its lifetime [48]. The ICN architecture building blocks enabling the shift from a host-centric to a content-centric paradigm are elaborated in the following subsections.