# A Systematic Literature Review on Military Software Defined Networks
## 4 Identified Significant Research Contributions
### Architectures
Further validation is proposed, given the limited size of the examined topology, but also limitations related to node mobility and communication patterns, which have not been captured extensively under the realistic characteristics of tactical deployments. Nonetheless, the experimentation method is sound and provides viable insights towards future work, which as the authors suggest will include extended configurations. [PERSON] et al. [19] proposed an SND and Network Function Virtualization (NFV) based architecture, within the highly mobile environment of Unmanned Aerial Vehicles (UAV) infrastructures. The proposed architecture aims at (i) improving situational awareness for pilots and payload operators during UAV missions, (ii) increasing continuity of services in deployments with weak backbone infrastructure, (iii) reduction of latency in applications related to situational awareness, and (iv) reduction of the requirements imposed on the backbone infrastructure in cases of outages or traffic spikes. Each UAV is defined as a host, with mobile ground vehicles operating as switches, which route traffic towards the pilots in command and mission payload operators, in accordance with predefined OpenFlow rules. The chained containers hosting the VNFs (Virtual Network Functions) are located in the ground vehicles, while the SDN controller is located at the central command center. The authors implement their architecture with Linux based chained containers for instantiation of the VNFs and the Python SDN controller. Validating their architecture, the authors utilize scenarios that focus on pilot saturation with alerts. The results support an improvement of situational awareness, due to the programmability of reports related to emerging challenges, and an overall improvement in terms of resilience. Furthermore, high mobility patterns are supported through the integrated distributed selection of resilient links with sufficient capacity and availability. [PERSON] et al. [20] describe a framework that leverages the benefits of the SDN paradigm, in order to guarantee end-to-end timing constraints in safety critical Real Time Systems (RTS). The advantage of using SDN in such systems is that it provides a centralized mechanism for developing and managing the system. Furthermore, such a global view is useful in providing the end-to-end delay limitation guarantees that are required. As the authors suggest, another advantage is that the hardware/software resources needed to implement the proposed framework are limited. A prototype is implemented as an application that uses the northbound Application Programming Interface (API) for the controller, which accepts a specification of flows that contain a classification, bandwidth requirements, and the delay constraints of each individual flow. The proposed solution is evaluated using the following two methods: (i) a performance exploration of the path layout algorithm design, and (ii) an empirical evaluation using Mininet, which demonstrate the effectiveness of the end-to-end delay guaranteeing mechanisms. As noted, most hardware switches limit the maximum number of queues that can be allocated to flows, while the presented realization mechanism reserves only one queue per port for each flow, leading to the depletion of available queues. Moreover, [PERSON] and [PERSON] [21] provide a basic evaluation of SDN within coalition networks, and address research challenges related to the dynamic ecosystem of military networks. In particular, the authors focus on dynamic wireless networks and network controller topologies, by presenting the identified challenges and vulnerabilities. The challenges are reflected by the constraints of military networks such as (i) limited bandwidth, (ii) unreliable wireless connectivity, (iii) dependencies of the network controllers, (iv) east-west control plane channels, and (v) data integrity in open networks.