# ICENET: An Information Centric Protocol for Big Data Wireless Sensor Networks
## 4 ICENET--Information Centric Protocol for sEnsor NETworks  
ICENET is composed of three distinct elements, which operate independently: (i) A tree-based routing structure supported by RPL, for data message delivery; (ii) an overlaid routing topology based on information, for propagation of queries (interest messages); and (iii) a soft-state control mechanism, for reliability. Figure 3 shows the task attributed to each ICENET component. We assume that queries are injected into the network by a gateway node (root), while the sensor nodes send data only in response to these queries. The tree-based structure constructed by RPL is in charge of delivering data messages to the gateway, while the overlaid routing topology, based on information, is in charge of forwarding queries to data sources. Data messages are relayed from child nodes to the parent node until they reach the gateway. Queries are forwarded from parent nodes only to child nodes, based on the information provided by them. ICENET nodes work collaboratively, in a distributed approach, to deliver queries to potential data sources. Centralized approaches are infeasible in large-scale deployments, since global network  
Figure 3: Information Centric protocol for sEnsor NETworks (ICENET) components. Figure 2: (**a**) A general wireless network. (**b**) Downward route construction. (**c**) Upward route construction. (**d**) Data traffic. information is often required. In dynamic environments, centralized approaches are even more harmful, because they introduce delays and communication overhead to maintain the network information updates. In order to prevent flooding, which must be avoided in large-scale IoT deployments [37], the parent node forwards a query only if the child nodes have routes to the data sources. For this, the nodes maintain a forwarding table (called the FIB) which stores the information provided by their child nodes. In comparison to other approaches, the size of this table is significantly reduced as it does not store routes for the entire network. If we apply a conventional approach in large-scale networks, the size of the tables maintained by the nodes may overflow and lead to network collapse. Another advantage of hierarchical structures, such as trees, is to avoid the use of a frequent route discovery mechanism. In addition, trees are the most appropriate structure for data aggregation and periodic data transmission [30]. The information-centric paradigm allows clients to retrieve data without the knowledge of the addresses of the nodes. As in [47], we assume that information is extracted from the network using a query language. Consider, for instance, an environmental WSN (EWSN) covering a large monitoring area containing a lake. A query example, intended to collect information about temperature and humidity in the lake, is shown in Figure 4.  
Nodes decide whether to forward a received interest message, according to the information stored locally in the FIB, whose entries are composed of attribute (ATTR), reachable region (REGION), and data sources (DS):  
\[\text{{FIB Entry}}=\{\text{ATTR},\text{REGION},\text{DS}\}.\]  
The ATTR field refers to some information (physical monitored parameter), the REGION refers to a specific location, and DS represents the set of child nodes that provide the information. Only interest messages received from the parent node are processed. Interest messages received from nodes other than parents are discarded. Nodes store a received interest in a local table, called the Icache (Interest Cache), until it expires. Icache entries are composed by identification (ID), timestamp (TS), attribute (ATTR), REGION, expiration time (ET), and data sample rate (SR):  
\[\text{{Icache Entry}}=\{\text{ID},\text{TS},\text{ATTR},\text{REGION},\text{ ET},\text{SR}\}.\]  
The ID field refers to an identification assigned to the interest by the gateway and TS determines a specific time point to start the data collection.