## 3 Novel Taxonomy for SSNs
### High Level Virtualization
#### 3.2.1 HLV Using Network Level Virtualization  
This branch of HLV is applied over the whole network, to participate it into smaller areas. While using two types of solutions, the first is Virtual Network/Overlay Sensor Networks solutions and the second is Cluster-based solutions. \(\bullet\) HLV using Virtual Network/Overlay Sensor Networks solutions  
These solutions provide network resources' sharing and facilitate the communication among sensors in different administrative domains. Thus, this section will briefly list them:  
\(\bullet\) **Multi-layer architecture for VSNs**[22]: this article proposed a three layer architecture to create multiple VSNs over the deployed WSN, which will give multiple applications the ability to run concurrently over this SSN. It uses overlay to facilitate the data exchange among the nodes in different VSNs. It consists of three layers, as seen in Figure 20.  
Figure 19: High Level Virtualization (HLV) of SSNs. The first layer represents the physical WSN that contains heterogeneous sensor nodes, a new generation of them can participate in the overlay, but the older cannot, thus it also contains a Gates-to-Overlay entity to support the earlier sensors to participate in the overlay, the second layer is the virtual sensor layer that abstracts the concurrent application and management tasks implemented over the physical sensor to become virtual sensors, the third layer consists of multiple overlays, and each one uses some virtual sensors as members that are dedicated for a certain application; it also proposes separate paths for data and control messages. This architecture is based on four principles, the first one is caring about the deployment of the new application as an overlay on the top physical network, the second one is multitasking processes on the physical sensor, while the third principle is the overlay operation on sensors that do not support the middleware, which will delegate the operation to other sensors, finally the fourth principle provides two separated paths for sending two types of data between the infrastructure and the overlay applications, where the sensor's data is sent through data path and control data is sent by the signaling path. There is no performance evaluation presented for that proposed architecture. * **Managed Ecosystems of Networked Objects (MENO)**[53]: This article presents a new concept that aims to create a smart network architecture that collects all of the internet connected objects using the combination of network virtualization technology and clean-slat end-to-end protocol [54] rather than the usual gateway based solutions that provide security, firewalling, protocol translations, and intelligence by gateways at the border of the Internet and the resource constrained networks. This combination will provide a new open minded platform, that offers open and secure communication methods and services that are able to connect sensors as any other IP-smart object over the internet, that facilitate the application development and innovation. The proposed layered architecture is shown in Figure 21. It consists of four layers, the first one represents the physical network infrastructure that contains a diversity of network technologies, the second is the logical network layer above it that is implemented to connect the cooperated objects, then the third layer presents a design of novel end-to-end protocols that introduces a common language between all connected objects, and the last layer presents the powerful API for services and application development. This concept has no implementation yet, and there is no available performance evaluation. Figure 20: Multilayer Architecture for Virtual Sensor Network (VSNs). * **IoT-Virtual Networks (VN)**[55]: Internet of Things Virtual Networks is a secured virtual network for both resource constrained and non-constrained objects that need to co-operate under the umbrella of virtual networks, it is based on the idea that was proposed by MENO, it uses end-to-end communication between networked objects.