# Digital Twin-Driven Virtual Network Architecture for Enhanced Extended Reality Capabilities
## 3 Architecture's Proposed Approach
### Extended Reality Functions' Deployment Approach and DTN Operation--Integration  
Since this paper's primary focus is the enhancement of the network experience assisted by XR technology, this subsection introduces the deployment of the XR services and their integration with the DTN. In addition, the traffic flows regarding the service operation are illustrated. First, it is important to emphasize that the set of different extended Reality network services composes the XR Functions (XRF) system, which enhances the proposed DTN. In order to facilitate the construction of new network services based on XR technology, a variety of approaches can be adopted; as previously stated in Section 3.2, the utilization of NFV as a development tool is recommended. According to [47], the NFV architecture offers a wide range of advantages that can be exploited within the DTN environment to facilitate the XR services' deployment. Among the advantages of NFV architecture are: scalability and flexibility, efficient resource utilization, dynamic service provisioning based on Virtual Network Functions (VNFs), ease of integration with different technologies and digital environments and standardized development platforms (OpenNFV, OpenMANO, OpenStack, Kubernetes, etc. ), among others. While the XRM Service Interface can serve as platform to receive the XR creation request, to construct a new XR service within the DTN, the XRM Service Controller has to consider:  
Figure 14: DTN data flows. * Network model access: The manner in which the XRM Service Controller accesses the DTN network models has to be defined. APIs can be employed to facilitate the retrieval of the DTN network models (stored in the DTM Model Storage block). * Identify the requested XR network service: in this step, the requested network service has to be analyzed and decomposed into smaller portions of the network function. * VNF's deployment: once the network functions that comprise the XR requested service have been identified, the VNFs can be constructed. The approach to employ smaller VNFs has the advantage of function modularity. The deployment of the VNFs has to consider the DTN network model information. * Construct the XR service: the XRM service controller has the task of constructing the XR service based on the NFV architecture. * Extended Network Model definition: once the XR service has been constructed, it has to be modeled by the DTM Modeler and stored in the DTM Model Storage identified with a unique tag ID for future XR service access. In the context of the integration of the Digital Twin Network (DTN) with the extended Reality (XR) services, key aspects must be considered: real-time data access, data processing, XR interfaces and simulations, as is explained in [48; 49]. The extended Reality Manager (XRM) shown in Figure 8 and explained in Section 3.2 has the ability to achieve the aforementioned integration:  
* Real-time data access: The DTN real-time data are realized as network models processed and updated by the DTM Modeler and stored in the DTM storage block. Consequently, the XRM Service Controller needs first to classify the service as a reading or writing service, and then access the stored network models through the DTM Modeler. * Data Processing: Data processing for XR integration is supported by two blocks: the XRM Service controller and the DTM Modeler. The former has the responsibility of processing the retrieved network model and integrating it with extended data, while the latter has to re-model the \"Extended Network Model\". * XR Interfaces: The XR interfaces are approached with the XRM Service Interface. As stated in Section 3.2, this block has to process the input and output information according to the input/output format (voice, images, touches, etc. ); consequently, it has to process the DTM Network Builder information in order to allow the users to know and realize the service's response.