# Designing a Softwarized Network Deployed on a Fleet of Drones for Rural Zone Monitoring
## 2 Video Monitoring Platform Description
### Platform Orchestration  
A platform element that plays a very important role is the backbone network orchestrator drone, in the following indicated as _orchestrator_. It is a dedicated drone communicating with all the platform components through the backbone network. Its goal is to coordinate the behavior of all the elements of the NFV infrastructure (NFVI) [51], that is, the SDN switches and the virtual machines (VMs) used on the network nodes to run both the network functions and the elements of the video broadcasting infrastructure, i.e., the acquirers and the edge streamers. More specifically, tasks of the orchestrator are allocating, migrating and terminating VMs, controlling traffic paths, managing and orchestrating service chains according to the run-time evolution of the network traffic, the requirements of the video monitoring platform provider and the service-level agreements (SLAs) with the customers. The orchestrator architecture, following the management and orchestration (MANO) document [28], is shown in Figure 4. Its main elements are:1. Platform Front-end: it is the manager of this specific service of video monitoring, and works as the access interface of the orchestrator for the users of this service. The Front-end is an http server aiming at handling the RESTful requests from clients. Application data are stored in a relational database containing the following information: Users with their profile and subscription agreements For each video transmitter, its geographical position and its access permissions For each user, the set of portions of rural to be monitored, the list recorded contents with the location of the stored sub-streams to compose it, and other additional information like the triggering alarms. When clients access the service through their web-based devices or their dedicated mobile Apps, they directly communicate with the platform front-end, which uses his database, in order to synchronize the information with the local user's devices. Then, for each action requested by the users, the front-end receives a request and forwards it to the NFV orchestrator residing in the management and orchestration (MANO) segment to be processed and implemented on the video broadcasting infrastructure. More in depth, as a first action, the front-end verifies the user identity. If the entering user is a client, the front-end sends it the list of the available transmitting elements and their current localization on the monitored area. The client can furthermore choose to access his own archive of previously registered contents. On the other hand, when new transmitting elements are attached to the backbone network, or some transmitter drone changes its current location, the platform front-end notifies this to the NFV orchestrator to reconfigure the mesh backbone network and the video broadcasting infrastructure. 2. Virtualized infrastructure manager (VIM): it is the core application of a softwarized network, acting as a sort of operating system for the network; it sends rules to the hardware and software nodes of the NFV infrastructure about port forwarding, and chooses optimal paths for application data delivery; in addition, it decides the amount of resources, in terms of bandwidth, computing and memory, that each node has reserved to support each elementary service;  
Figure 4: Orchestrator architecture. NFV: network functions virtualization. 5. VNF manager: it has the capability for managing the lifecycle of virtual machines running both network (e.g., deep packet inspectors, load balancers) and application functions (i.e., all the functions related to streaming, forwarding and storage). Its choices are based on the rules and information coming from the NFVO element, and is in charge of creating, migrating and destroying VMs, communicating with the hypervisors running on the network nodes;
6. NFV orchestrator (NFVO): it gathers information about the network (topology, number of connected clients, required contents, availability of backbone node drones, etc.)