# Insights from the Experimentation of Named Data Networks in Mobile Wireless Environments
## 3 Integrating NDNs in Smart Cities
### Named Data Networks  
Currently, the Internet communication model TCP/IP is based on a host-centric network vision paradigm, where the request for a given content begins by locating and identifying the node in which the content is stored, followed by the establishment of a connection from which the communication of the request to acquire the content will be made, which is repeated for each request made by a consumer, as seen in Figure 1.  
This type of model was not developed taking into account some requirements that are of interest to the IoT, such as the large number of connected devices, node mobility support, in-network caching or the security of the transmitted contents, but was rather a model that only considered the connection between a limited number of devices/computers. Some approaches have been proposed by many communities to solve these problems and needs, one of them is NDN, which places information dissemination at the centre of the network layer.  
In NDN architectures, the node interested in some content (Consumer) requests it from its neighbors through its unique name without any indication of location (IP for example). The network nodes disseminate this request until it reaches the node where the desired content is located, a Producer or any other node with the Content on its cache. Thus, communication between nodes follows a Request-Response exchange model with native multicast support, which is quite efficient in mobile environments [3]. The Producer  
Figure 1: TCP/IP vs. NDN paradigm.  
sends the requested Content using the opposite path to that taken by the Interest, following a receiver-oriented approach.  
In an NDN architecture, the Consumer requests Contents without knowing the providing host, and the communication follows a receiver-driven approach, i.e., the data follow the reverse route of the request (Figure 2a). The system is then responsible for mapping the requested data and its location. An NDN architecture is characterized by the adopted approach on each of the following key functionalities: naming and name resolution, routing and forwarding, and caching [22]. NDN nodes use three structures in the Forwarding process (Figure 2b). The Forwarding Information Base (FIB) contains the names of a given Content, provided by the routing protocol, and associates them with the interfaces on which they were received. In addition to the FIB, NDN nodes use two other tables: Pending Interest Table (PIT) and Content Store (CS). Each PIT entry contains the name of the Interest packet and the respective interfaces through which it arrived at the node. On the other hand, the CS stores the data packets and works as a buffer managed by caching policies [3; 23].  
In short, in Named Data Networks the contents are independent of their physical location, such as IP addresses, being accessible from anywhere on the network. In addition, caching mechanisms speed up their access by distributing and keeping copies in the network nodes. The forwarding and routing mechanisms of NDNs make the nodes completely independent, not requiring the previous formation of networks, clusters or platoons for communication to flow between them. These characteristics better meet requirements such as scalability, heterogeneity and dynamicity that are increasingly present in new applications for metropolitan networks.  
Yet, despite all the expected benefits of solutions that address the limitations of Internet protocols, due to their widespread use, it is not expected to be simply phased out, but a gradual replacement over time [24]. In this direction, our option was to design an architecture that allows peaceful coexistence between the IP-based network and the NDN solution. For a better understanding of such solution for coexistence and shared use of devices, below we give an overview of the city-scale communication infrastructure in the ATCLL.