# A Systematic Literature Review on Military Software Defined Networks
## 4 Identified Significant Research Contributions
### Architectures  
A multitude of articles in this category investigate topics related to network monitoring and control. [PERSON] et al. [PERSON] et al. (2015) proposed a battlefield networking architecture, enabling the deployment of SDN based applications and policies. The article examines in detail the benefits and disadvantages of (i) centralized, (ii) hierarchical, and (iii) federated approaches, comparing the two later and discussing in detail the supported policy based management solutions. Furthermore, the authors briefly discuss security implications and proceed by examining two use cases related to (i) bidirectional video streaming, and (ii) task coordination. Overall, the article is comprehensive and consistent with current research trends, although further evaluation is suggested. Furthermore, [PERSON] et al. [PERSON] et al. (2016) proposed a joint exploration of the SDN and Delay Tolerant Network (DNT) concepts, in order to address the specific constraints and problems arising at the last-mile Tactical Edge Networking (TEN). The proposed approach takes under consideration the resource constrained devices used by troops in the field, while it benefits from the programmability of SDN, and the ability of DTN to handle link outages. Two use cases are examined in order to highlight the applicability of the proposed architecture. The first sets out a scenario that highlights some of the SDN features within network partitions supporting a non-elastic application. The second use case deals with the management of communication between heterogeneous nodes in the TEN, which spread across different partitions. [PERSON] et al. [PERSON] et al. (2017) suggested a prototype framework for (i) network control, (ii) traffic prioritization management, and (iii) radio/protocol integration, with the use of SDN for emergency response and military networks. Initially, the article contributes with a two-tier hierarchical SDN controller setup, which exposes a modular interface for the management of wireless networks. Furthermore, the authors proposed a framework that allows the integration and interoperability across distinct wireless network technologies. Both frameworks are presented in detail, related to the desired functionalities of (i) traffic prioritization, (ii) remote network management, and (iii) multiple radio integration. Accordingly, the authors present the results of their initial evaluation process, presenting a small scale prototype implementation. The article investigates an interesting research path, but further evaluation and development is required, since the presented validation approach is small in scale for comprehensively highlighting the overall benefits. Moreover, [PERSON] et al. [PERSON] et al. (2018) described an architectural framework for traffic management in tactical networks, combining elements of Mobile Edge Cloud (MED) and SDN, to allow optimal network reactivity to the wireless link variations. The proposed framework can be decomposed into four layers, namely: the (i) \"waveform layer\" which consists of the multiple deployed programmable radios, the (ii) \"SDN layer\" which contains a virtual switch and the SDN controller, the (iii) \"application management layer\" which is mapped to the MED where the applications run, and the (iv) \"mobile edge controller\" which is a module that bridges the other three layers. Channel state information are periodically measured and aggregated at the controller, which routes the traffic in accordance with these information and dedicated policies deployed within the \"mobile edge controller\", in order to detect network saturation or bottlenecks and react accordingly. The authors have implementedthe proposed architecture in a test-bed that emulates a platoon level tactical network, abstracting the backbone infrastructure, towards the validation of their results. The utilized test-bed is described in detail within the article, while two distinct scenarios are used for validation purposes that primarily relate to network management.