# Dynamic Virtual Network Slicing and Orchestration for Selective MEC Services over Wide-Area SDN
## 4 An Automated Virtual Network Slicing Experiment Using Globus Online  
This section describes a network automation use case that can be applied to dynamic MEC resource allocation services in terms of cognitive virtual network slice creation and management. The use case in this section takes advantage of Globus Online, which is a grid-oriented, end-to-end, and disk-to-disk large file transfer system, and the VDNO system that coordinates VDN and Kubernetes for containerized resource allocation combined with a dedicated virtual network slice. In order to utilize Globus Online, data transfer nodes (DTNs) are allocated by VDNO in the first place. Globus Online manages each end-system resource to be registered as a DTN endpoint to store a large volume of data and transfer the massive file to another DTN endpoint.  
VDNO can generate and manage DTNs dynamically as containerized resources connected to the KREONET-S infrastructure, which enables the DTNs to be included in the specific virtual network slices on demand. If a containerized DTN is registered at Globus Online, it becomes a DTN endpoint which transfers large-scale data to another endpoint using a high-performance file transmission application such as GridFTP on the basis of its simplified user interface. Globus Online basically offers Open APIs for authorization (Auth) and file transfer (Transfer). The Auth API manages the permission and access control of the Globus Online system and the Transfer API is responsible for endpoint registration, listing, and removal, as well as data transfer.  
Originally, VDNO interacts with the VDN and Kubernetes systems, and the interoperability of VDNO expands to work with Globus Online for the automated virtual network slicing. First, VDNO acquires endpoint information (i.e., containerized DTN information) by calling the Auth APIs and then converts the acquired endpoint information to the JSON (JavaScript Object Notation) data model that can be recognized by ONOS. Once VDN identifies real-time communication between the DTN endpoints on the basis of the JSON dataset delivered by the ONOS NBI, it automatically provisions an end-to-end VDN slice including the DTN endpoints to guarantee high performance of data transfer up to 100 Gbps over KREONET-S. For the real-time detection of data transfer, it is necessary to identify data communications between the DTN endpoints registered at Globus Online by constantly monitoring OpenFlow PACKET-IN messages using the PacketProcessor API provided by ONOS. Additionally we implemented a VdnFwdManager module in the VDN system, which makes a request to the VdnManager module to create each virtual network slice automatically when a PACKET-IN event is detected.  
On the basis of the created virtual network slice, the disk-to-disk data transfer performance is measured by Globus Online, as shown in Figure 7. The source and destination DTN endpoints are generated as containerized resources (Kubernetes PODs) by VDNO in two locations in Seoul and Busan in Korea, where the endpoint residing in Seoul (k8s-s1-dtn.kreonet-s.net) transmits a 10 GB file to another one (k8s-bs-dtn.kreonet-s.net) in Busan. The two endpoints participate in a dynamically created 1 Gbps virtual network slice, consequently gaining a measured throughput of 98.34 MB/s (around 790 Mbps), which indicates a similar network performance to that evaluated by a disk-to-disk data transfer experiment between two fine-tuned physical servers connected with a back-to-back dedicated 1 Gbps physical network link.