# A Systematic Literature Review on Military Software Defined Networks
## 4 Identified Significant Research Contributions
### Basic Evaluation  
Five articles provided a basic evaluation in respect to tactical, military, and naval networks with main focus on the control layer. [PERSON] et al. [37] demonstrated and evaluated the implementation of an OpenFlow SDN controller within tactical scenarios, seeking to identify how such implementations can enhance agility, scalability, and network management flexibility for the tactical edge. The article provides a comprehensive presentation of OpenFlow, in terms of overall operation, matching criteria and internal messaging between the controller and the switches. Accordingly, the article briefly describes the Mininet prototyping environment, which is further utilized for the development of an experimental setup, towards verifying the capacity of OpenFlow to satisfy the requirements of the tactical environment. The examined test cases refer to (i) diversion networking, (ii) central policy management for access control lists, and (iii) the distribution of SDN controllers. The article is comprehensive, and promotes further evaluation for providing proof that OpenFlow can be aligned with the requirements of the tactical environment.  
[PERSON] and [PERSON] [35] proposed an SDN based approach for load balancing within naval military scenarios. The authors construct an experimental setup using Mininet, and utilize Floodlight as the protocol for the communication among switches and the controller. The experimental setup consist of five WAN (Wide Area Network) switches, which correspond to three ships and two on-shore data centers. Furthermore, the scenario assumes three types of traffic with distinct priorities. The article offers a detailed presentation of the evaluation scenario details, while the results highlight the benefits of corresponding SDN implementations, in terms of network programmability and management automation, but also in terms of load balancing and reliability.  
Additionally, [PERSON] [52] described an investigation into five open-source controllers using a specific set of criteria based on the characteristics of these networks. A qualitative investigation compared the controllers based on their state handling and failure recovery mechanisms, and resulted in the selection of two controllers for further investigation. Further quantitative tests were performed on these two controllers, in order to determine which was more suitable for deployment in an airborne environment. [PERSON] et al. [57] proposed an architecture that serves as a guide for current and future experimentation on trust management and protection in tactical SDN when used with mobile nodes in a coalition operation. However, this work does not discuss thoroughly the security of the information transported through the network, focusing on the protection and separation of different data flows. This separation needs to be robust and reliable, but it does not provide security services on the content of the flows. Finally, [PERSON] et al. [36] identified the key types of messages used in OpenFlow, and how their overhead is influenced by network characteristics in military networks. Furthermore, the authors presented a series of mitigation measures for reducing or eliminating the overheads, some of which are possible to implement within the current SDN standards, while others require further extensions. The authors perform an experimental validation to quantify and confirm their analysis, where the scenario is implemented using Mininet with OpenVSwitch as the switching element, and netem for performing network simulation.