# Logically-Centralized SDN-Based NDN Strategies for Wireless Mesh Smart-City Networks +
## 2 Related Work  
The smart community networks may benefit from the ICN approach as it can increase the network performance, reducing communication overhead, thanks to the in-network caching capabilities, as shown in [6]. However, ICN architectures, including NDN, lack of inherent mechanisms for supporting efficient NDN operation in challenging communication environments, such as WMN. In this context, content delivery and packet forwarding over such networks, with unstable wireless links, remains an open issue [12]. In this work, we study two different strategies for appropriate NDN path selection over WMN environments: (i) a dynamic approach with a reactive operation and (ii) a proactive one based on clustering evaluation of the quality of the wireless links. Here, we discuss a number of NDN-based solutions sharing similar design characteristics with the aforementioned strategies. Moreover, we divide the representative-related works into dynamic/reactive and cluster-based approaches, comparing them with the basic technical characteristics of our strategies (i.e., SDN-based centralized control and real experimentation over WMN), as illustrated in Table 1.  
Recent approaches have been trying to resolve NDN routing and forwarding limitations with SDN [27]. In [20], authors designed and evaluated an SDN-based routing scheme for CCN/NDN (SRSC) which fully exploits the NDN principles, and, thus, the Controller and the nodes communicate using NDN messages (exchanging control and information messages). Particularly, the controller makes the routing decisions, and the NDN nodes act as forwarding devices only, as in our case. In SRSC, the Controller only informs an NDN node of the entire path to the content and afterward, the NDN nodes communicate with each other (hop-by-hop), to create the specific path. In contrast, we selected the controller to communicate independently with each on-path node and configure the NDN network, because of the unstable mesh topology. In [21], the authors proposed an SDN-enabled Controller for multipath forwarding in NDN. The SDN controller analyzes the global view of the NDN network and makes appropriate forwarding decisions, according to the router states, the available forwarding paths, and the cached contents. The particular centralized solution improves the performance of NDN compared to a distributed multipath forwarding strategy, which relies on _a priori_ forwarding information and is inappropriate for networks with dynamic topologies, as in our case. Such solutions have been evaluated over a real-world WAN network, so frequent path changes and unstable topologies were not investigated in depth. Authors in [22] introduced an integrated SDN-NDN framework and modified NDN's FIB design to address FIB overflow. In particular, FIB overflow is affected by (i) a large number of different contents and (ii) long-lived FIB entries. In our work, we maintain the default NDN's FIB design and address those issues by creating short-lived FIB entries in the NDN network. In [23], authors target to improve the NDN performance through efficient content management, considering features of wireless communication. Their proposed solution \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Approach** & **Works** & **Centralized** & **SDN** & **Wireless Mesh** & **Real Experimentation** \\ \hline \multirow{6}{*}{_Ractive_} & SRSC [20] & ✓ & ✓ & X & X \\  & Multipath Forwarding [21] & ✓ & ✓ & X & ✓ \\  & Software-Defined NDN [22] & ✓ & ✓ & X & X \\  & SDN-NDN over WMN [23] & ✓ & ✓ & ✓ & ✓ \\  & **Our reactive strategy** & ✓ & ✓ & ✓ & ✓ \\ \hline \multirow{6}{*}{_Cluster-based_} & Cluster-based NDN Routing [24] & X & X & X & X \\  & LCRN [25] & X & X & X & X \\ \cline{1-1}  & NDN-based IoT [26] & X & X & X & X \\ \cline{1-1}  & PiGeon [6] & ✓ & X & ✓ & ✓ \\ \cline{1-1}  & **Our proactive strategy** & ✓ & ✓ & ✓ & ✓ \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Related Work Comparison.