# Digital Twin-Driven Virtual Network Architecture for Enhanced Extended Reality Capabilities
## 4 Architecture Modeling Approach
### Communication Protocol Requirements  
It is essential to analyze the requirements for enabling ON-DTN communication, as well as end device communications. Two different interface communications have been identified and are shown in Figure 18:  
1. ONM Edge Router--DTN Edge Router: The communication between both Edge Routers concerns the in-space data transmission scenarios. In order to establish the in-space communication channel between both Edge Routers, several considerations have to be taken into account; among the main issues to be considered are: * Bandwidth: since the available bandwidth is a limited resource, the amount of data to be sent has to be optimized; then, compression algorithms can be utilized. * Latency and Disruptions: In the space communication scenario that has been proposed, the latency will be in the range of tens of seconds to hundreds of seconds; also, the communication links will suffer from disruptions due to different conditions such as planetary orbits. Then, it results as being fundamental to mitigate the communication degrade in high delay and disrupting conditions with the aim to achieve the proposed system deployment. Alternatives such as the Delay/Disrupting Tolerant Networking with the Bundle Protocol (BP) can be envisioned as potential solutions.
* Security: Since the information shared between both Edge Routers can exhibit critical network information, the data integrity must be guaranteed and avoid unauthorized data access. Then, coding and encryption techniques can be adopted.
* Interoperability: it must be assured that both Edge Routers employ compatible standards, technologies, algorithms and protocols.  
In this scenario, since the communication between the ONM and DTM will suffer from high latency, the utilization of security and authentication mechanisms can incur an increase in jitter and delay in the aforementioned communication; however, such fluctuations are expected to be insignificant compared with the space communication latency, which ranges from tens of seconds to hundreds of seconds.
* Data Center--DTCD: Since both the clients and the Data center are hosted in the space station, the issues to be considered are different from the previous scenario. Among the main considerations are:  
* Environmental conditions: in the space station, space radiation could degrade the communication between clients and the data center.
* Bandwidth: since the clients can request XR services, the bandwidth must be guaranteed to support those requests.
* Accessibility and Security: In order to guarantee authorized accesses, API interfaces can be adopted. On the other hand, encryption techniques can be utilized to guarantee data integrity, as well as the TLS protocol.
* Communication Protocols: The space station communication established between DTCD's and the data center will not suffer the high delay and disruption conditions; however, the utilization of XR services and DTN navigation require small latencies. Then, UDP or streaming protocols can be implemented.  
In both cases, the three-way handshake mechanism must be considered. The aforementioned mechanism enable agents to negotiate communication parameters; the streaming protocols can leverage the handshake approach.