# A Systematic Literature Review on Military Software Defined Networks
## 4 Identified Significant Research Contributions
### Tools  
With a research contribution related to tools, one article provided a basic evaluation related to tactical networks. In this, [PERSON] et al. [46] assessed the integration of the SDN paradigm across tactical networks, discussing the expected benefits and potential threats. The article provides a comprehensive analysis of the characteristics of tactical networks, in conjunction with an overview of the architectural and operational attributes of SDN, aligning the two by extracting the expected benefits to the tactical user. These relate primarily to enhancements of information dissemination, service delivery, and link utilization. Furthermore, the authors provide an iterative assessment methodology regarding the performance gains by such an integration, the design options in respect to tactical SDN controllers, and challenges that need to be addressed. It must be noted that no extensive validation is provided within the article referring to the proposed methodology. Therefore, it is not clear if the results of the study are exhaustive, mutually exclusive, or if there are any identified interdependencies. Furthermore, three articles within this sub-category have a scope related to security, either directly related to military or distributed networks. [PERSON] et al. [44] described an OpenFlow-based test-bed for the validation of SDN security mechanisms--including both the mechanisms for protecting the SDN and the cross-layer enforcement of higher level policies, such as data-centric security policies. Such cross-layer security mechanisms are important in the context of software-defined infrastructure and implementation of new security paradigms, such as data-centric security. Furthermore, the authors demonstrate the functional correctness of the test-bed, as well as its suitability to provide validation and additional insight into the behavior of analytically designed security mechanisms. The authors present a low-cost implementation of a flexible SDN test-bed, specifically focused on security experimentation in respect to security services provided by SDN to both the network and application layer. The test-bed consists of seven switches (annotated S1 to S7), a controller, a server and a typical switch for VPNconnection. It can be split into two networks: a control network (connections between the switches and the controller) and a data network (connections between the switches, including the server). There is also a VPN network allowing remote configuration of all test-bed nodes via SSH protocol. All switches use the Ubuntu 16.04 operating system and OpenVswitch 2.1.1-based (OVS) implementation of OpenFlow protocol in bridge configuration. The test-bed can be also used for the validation of earlier results, obtained analytically or from emulation (e.g., Mininet) and simulation (e.g., ns-3) tools. [PERSON] et al. [48] proposed a redesigned untraceable Blind Packet Forwarding (BPF) method, based on the Public-key Encryption with Keyword Search for Restricted Testability (PEKS-RT) algorithm, in which the specific host IP address cannot be guessed. The main feature of this approach is that when the source host encrypts the destination host address, it includes the source host's private key, the destination host's public key, and the destination host address as parameters for encryption. Another feature is that the destination host generates the trapdoor value using the destination host address, the source host's public key and the destination host's private key. A centralized SDN controller is used for reducing the overhead of routing data processing of the existing method, increasing this way the operational efficiency. The authors describe a prototype implementation for the blind packet forwarding using PEKS-RT. Their approach is realized in the SDN environment using the Mininet emulator, where Open vSwitch is used as a switch and Floodlight as a controller.