# Insights from the Experimentation of Named Data Networks in Mobile Wireless Environments
## 1 Introduction  
Information Centric Networking (ICN) has been considered an alternative to the current Internet architecture, based on the TCP/IP stack, to overcome the drawbacks of host-centric architectures when applied to mobile Internet-of-Things (IoT) networks [1]. Such drawbacks are the frequent topology changes and intermittent connectivity caused by the mobility of the network nodes. Conceptually, in ICN each piece of data has a unique, persistent and location-independent name that is directly used by the applications for content search and retrieval. Therefore, ICN enables the deployment of in-network caching and content replication thus facilitating the efficient and timely delivery of information. Additionally, the publish-subscribe concept adopted by the ICN architecture, allied to a location-independent data identification, provides an efficient support for users' mobility. Amongst the several ICN architectures, the one receiving more attention by the research community is the Named Data Network (NDN) [2], a pull-based network system where the Consumer requests the Content by sending an Interest packet. This packet is relayed by the network nodes until it reaches the Content, either at the Producer or cached at some node on the network. It is up to the node that owns the Content to send it along the reverse path, taken by the Interest, until it reaches the interested Consumer. Such architecture has been designed for infrastructured network topologies, with point-to-point links, and its application in mobile wireless environments requires the modification of some of the heuristics used in the NDN, especially those related with the Content forwarding [3]. Similarly, the use of the NDN architecture in a publish-subscribe communication paradigm is not straightforward because each each data packet must precede an Interest packet [4]. Despite the touted virtues of the NDN paradigm, it is rare to find implementations or testbeds where such architecture can be tested under the same conditions as TCP/IP-based networks. The majority of the evaluation and comparison works based on non-simulation scenarios consider solely wired network infrastructures, or in a small scale. To the best of our knowledge there are no ICN/NDN implementations at city-scale with both wired and wireless communication links. To address this gap, we present a city-scale implementation of an NDN architecture, optimized to support both single-data-request and publish-subscribe communication paradigms, and the support for multiple radio access technologies in a mobile environment. Such implementation is currently installed in the communications infrastructure of the Aveiro Tech City Living Lab (ATCLL) ([[https://aveiro-living-lab.it.pt/](https://aveiro-living-lab.it.pt/)]([https://aveiro-living-lab.it.pt/](https://aveiro-living-lab.it.pt/)) accessed on 7 June 2022), and is open for experimentation, development, test and/or demonstration of concepts, products or services targeting the Information and Communications Technology (ICT) topics. In this work, we explain the steps needed to implement an NDN architecture in such type of environments, where network nodes share multiple radio access technologies, such as ITS-G5, IEEE 802.11, LoRa and cellular 4G/5G, and we discuss its performance in real-world conditions, targeting the dissemination of a given Content to mobile users. In summary, the main contributions of this work are:  
* The deployment of an NDN architecture over a real city-scale wireless communication infrastructure;
* The performance assessment of the NDN architecture in the presence of multiple radio access communication technologies;
* The analysis of how several network characteristics impact the performance of the NDN architecture in wireless mobile environments. The remainder of this paper is organized as follows. Section 2 overviews the related work about deployment of ICN-based solutions in real hardware devices, and consequently, in non-simulated environments.