## 4 Description of Different Deployed VPN Solutions  
To create a VPN, there are different solutions, both HW and SW (e.g., use Mikrotik RouterBoards, (\"Mikrotik \", [[https://mikrotik.com/](https://mikrotik.com/)]([https://mikrotik.com/](https://mikrotik.com/)) (accessed on 15 June 2022)) or implement the appropriate stack on your own server, in this case with Debian OS (\"DEBIAN OS \" [[https://www.debian.org/index.it.html](https://www.debian.org/index.it.html)]([https://www.debian.org/index.it.html](https://www.debian.org/index.it.html))) (accessed on 15 June 2022)), with peculiar properties depending on the chosen implementation. In particular, we will focus on three macro application scenarios:  
* A Site to Site scenario: (where two remote offices communicate securely), shown in Figure 2
* A Site to Multi-Site scenario: (where multiple remote offices communicate securely), shown in Figure 3
* A Road Warriors scenario: (in which multiple users from remote offices communicate securely with a particular local office), showed in Figure 4.  
These solutions provide encryption and integrity of data in transit by relying on encryption algorithms ranging from Blowfish to AES (128-512) up to implementations that use elliptic curves (e.g., ecp192). Depending on the type of device/network to be interconnected, various alternatives are available, especially in the case of Road Warriors (RW), passing from authentication via PSK + XAUTH (e.g., in IPsec) to that through certificates, or even to two-step solutions, through one-time password (OTP) or supplementary credential files (case RADIUS + VPN IPsec/OpenVPN/OpenConnect). In this work we wanted to make a \"field\" assessment of the current landscape both at the level of communication infrastructures (WIFI, CABLE 4G/5G), and at the level of devices that it is possible to connect (NUC, mini PC, Raspberry Pi, Smartphones). Involved variables are many, ranging from guaranteeing the widest support to the greatest number of devices and technologies, trying to guarantee the best performance with the same safety. Table 2 provides a summary of the implemented testbeds: from a description of the network infrastructure to the software used. Many of the architectures proposed were built in the projects mentioned above and are still in production. OpenVPN and Wireguard are part of the Cogito project to interconnect the cloud and local offices. One used IPsec in the Domus project to manage data exchanges and resource access policies. Finally, one used OpenConnect and OpenVPN in the RESNOVAE project for the same purpose. Moreover, given the exponential increase of technologies such as the IoT [37], and the consequent development of communication paradigms such as \"Fog Computing\" or \"Cloud oriented approaches\" (e.g., AMAZON AWS), or multisite clusters (e.g., realized through Kubernetes [38]) both on fiber/PSTN carriers and on 4G/5G carriers, this ever-growing volume of data, also in compliance with the recent \"General data protection regulation\" (GDPR) regulations, must be managed properly. Another great advantage, deriving from the use of the OpenWRT (\"OpenWRT Project \", [[https://openwrt.org/](https://openwrt.org/)]([https://openwrt.org/](https://openwrt.org/)) (accessed on 15 June 2022)) operating system, allows the implementation of these technologies on all models of compatible routers and devices. The wide range of supported \"bridges\" allows, especially in the case of IoT networks, to interface with third-party protocols, to be used as a perimeter gateway, such as LoRa and Zigbee, as well as the classic ones supported by TCP/IP stack. If you consider that the x86-64 versions also easily support virtualization, you can create Fog networks of micro-services and IoT multi-protocol with negligible figures and connect them securely. An example could be given by the installation of outdoor sensor networks on areas covered in WAN by 4G/5G networks and locally configurable and processable with an \"Edge Computing\" approach. Figure 4: Site to Road Warriors VPN Scenario.