# Digital Twin-Driven Virtual Network Architecture for Enhanced Extended Reality Capabilities
## 3 Architecture's Proposed Approach
### System-Supporting Architecture
#### 3.2.2 Digital Twin Manager (DTM)  
The DTM is the entity that controls and manages the DTN and receives the network information from the ONM. The DTM modules are presented as follows:  
* Edge Router: This is designed to serve as a communication interface, enabling the transmission of DTN status information to the ONM and the reception of ON information from the ONM. It is fundamental that the Edge Router is designed with the intelligent ability to determine the optimal transport protocol according to channel conditions such as disruption time and available bandwidth, among others, to guarantee a successful packet delivery to the ONM. * Traffic Classifier: This is responsible for classifying the incoming data packets from the DTM Edge Router into control packets, which are utilized for DTN creation or synchronization, and data packets which are destined for DTCDs. The data packets are directly forwarded towards the Content Delivery Agent, while the control packets are forwarded either directly to the Modeler (to create a new DTN) or to the Network Synchronizer (to update the DTN model). * Network Synchronizer: This has the function of receiving ON \"Event\" data and forwarding it to the DTM Modeler. This Synchronizer has to be designed with the intelligence to manage and process the \"event\" information. With the objective tooffload the Modeler processing capabilities, the Synchronizer must be supplied with a set of algorithms aimed at: Data Filtering to optimize the data processing and ensure that the relevant data are posteriorly sent to the Modeler (these algorithms can be based on Kalman Filter algorithms); Updating-Priorities Establishment with the aim to carry out an orchestrated synchronization based on the event's relevance (Neural Networks can be implemented to analyze the priority based on previous synchronization events); Updating-Dependencies establishment to guarantee the network statuses' consistency (dependency graphs can be envisioned as a solution); Synchronization Algorithms, which can be based on network model difference detection algorithms such as delta or Rsync. The aforementioned algorithms can be analyzed in future work. Since the proposed scenario involves space communication between the ONM and DTM, synchronization can be compromised due to the constraints perceived in space scenarios; mitigation by means of buffer/queues mechanisms or different transport protocols, as outlined in Section 3.1, is crucial to alleviate synchronization issues. * Modeler: The Modeler is in charge of selecting from several network models (adjacency matrix, knowledge graph, among others) that are capable of managing the appropriate network model, ensuring the compatibility with the network model employed by the ONM and considering the modeling technique according to the algorithms employed or the accessibility to the stored model. Once the Modeler has processed the DTM model, the model has to be stored in the Storage Module. In addition, the Modeler has the capability to update the DTN model, stored in the storage module, with the \"event\" information received by the Network Synchronizer. Moreover, when the Modeler receives an \"Extended Network Model\" along with a service request from the XRM Service Controller, the Modeler has the task of determining whether the current DTN model has to be replaced by the \"Extended Network Model\" (writing services) or the \"Extended Network Model\" has to be stored and tagged with an XR Service ID (reading services) for a later XR Service request. * Model Storage: This is responsible for storing the processed network model by the Modeler. Additionally, this module must enable access to stored models for the Modeler; thus, queuing techniques are needed. * Network Builder: This is responsible for the DTN deployment by the consequence of receiving the modeled network information. Furthermore, it is required to continuously transmit \"Network Status\" beacons to the Status Control to achieve an autonomous DTN management process.