## 2 NDN-Based Wireless Mesh Networks
Thereafter, a new consumer requests the same content (\(Y\)) by sending interest packets represented by red or light grey, heavy-dashed arrows, Step 2. In this case, the interest packets do not reach the producer. Instead, this request is satisfied by an intermediate NDN node in the mesh backbone that has the content in its CS, as indicated. If nodes in the mesh backbone are not able to cache contents, all the consumers' requests for \(Y\) will be forwarded to the producer. In this example, in-network caching avoids bottlenecks near to producers, i.e., NDN reduces medium competition and traffic interference. There are two main storage policies proposed for NDN-based WMNs: reactive and proactive caching. Reactive caching policy evaluates whether received content will be cached or discarded based on the cache update. A simple way to use the reactive caching policy is to store contents only after an interest packet has been sent. On the other hand, proactive cache policies infer which contents should be predictably cached before requests arrive. In this case, nodes can cache a content even if there is no active PIT entry for this content. The use of a proactive cache in NDN-based WMNs can improve the average throughput, because nodes may take advantage of the broadcast nature of the wireless medium to store contents that have not yet been requested. Several proactive caching strategies use algorithms that predict which content should be cached based on consumers' demand profiles [18]. [PERSON] et al. stated that the cache policy must take fading and interference on the wireless NDN into account [18]. These problems are shown when content is cached on distant neighbors instead of the nearest neighbor of the consumer. Therefore, the consumer receives the content from distant nodes where it is more prone to suffering interference from the nearest nodes along the path. In addition to in-network caching, NDN-based WMNs can also benefit from the broadcast nature of the wireless medium to disseminate interest packets. Hence, when a node sends a packet, more than one neighbor can listen to this packet transmission. Neighbors are thus forwarding candidates which  
Figure 1: NDN-Based Wireless Mesh Networks. forward a request or content. These multiple forwarding candidates increase the probability of a packet being delivered to the producer or to forwarding nodes, which are temporarily able to provide content from their caches. Both the broadcast nature of the wireless medium and the way contents are requested, however, impose challenges to the deployment of NDN-based WMNs: the broadcast storm problem. With NDN, each node forwards an interest packet received for the first time. Then, every neighbor of this node that receives this interest will repeat the same procedure. We assume that nodes are often equipped with only one wireless interface. In this case, the interest packet is forwarded through the same reception interface, and all nodes in the transmission range of the forwarding node will receive the packet, even the node that previously forwarded this. Depending on the interest sending rate, nodes may experience a broadcast storm of interest packets. The consequences, in this case, are both an increasing medium access time and number of collisions. Collisions are caused by nodes that are in the same path used to obtain the content or by nodes that are closed enough to interfere each other [2]. Techniques have been proposed for wired NDNs to avoid the broadcast storm caused by interest packets. A simple technique is to define a rule per interface that states that interest packets must not be forwarded to the receiving interface. This technique, however, is not suitable for NDN-based wireless networks. There is no way to filter interest packets based on the forwarding interface because nodes are typically equipped with only one interface. In Sections 3 and 4, we discuss proposals to avoid the broadcast storm problem in WMNs.