## 4 Major Components of Network Slicing System
### Intent-Based Networking (IBN) Tool
#### 4.2.4 OSM Policy Configurator  
The IBN tool is a general system that supports multi-platforms, which requires a variety of policy configurators for each platform. The responsibility of these policy configurators is to converts the user contracts into an appropriate format required for a specific platform. In our work, we have developed three policy configurators for different platforms OSM, M-CORD, and RAN but we used two policy configurators OSM and RAN for developing the E2E Network slicing system. In this section, we will discuss the OSM policy configurator and how it works. The working details of this configurator is as follows; the main purpose of OSM based policy configurator is to converts the service graph information into the JSON string format because OSM accepts policy descriptors in this form.  
OSM policy configurator consists of three different engines, namely, VNF descriptor creation engine, NS descriptor creation engine, and NST Creation engine. Moreover, the first VNF descriptor engine contains three modules named basic information, VDU information, and connection point. The working of each module is as follows; the basic information module stores basic information, for example, name, description, and ID, etc.; similarly the second module VDU information can be used to record the information of resources, for example, required storage and RAM, etc.; thirdly, the connection point module stores the information related to ports and interfaces which are required for making connections. After that, all module performs their tasks and produce the JSON string that contains all configuration required for a VNF. The NS descriptor creation engine encompasses four main components: such as basic information, VNF descriptor (VNFD) information, connection ports information, and VLD information respectively. The working of the first two components are similar to the VNF descriptor engine but the third component VNFD information stores the information about specific VNFD for a specific NS descriptor. The last component stores the information of virtual links between different VNFDs.  
The last module named a network slice template (NST) generation which consists of three components basic information, NS descriptor information, and VL descriptor. This module uses the information which is provided in the NS descriptor previously and generates the network slice information in the form of the template. The next VL descriptor information component stores the information for establishing a connection between different network services. After that, it can transfer the NS template information into the next module OSM for further processing. All the modules work together and generate the descriptors in JSON format, these modules are also dependent on each other because the next module has used the descriptor information of the previous module. Afterward, the generation of all descriptors in the JSON string format will forward to the onboarding module for storing them in the OSM repository. These onboarding modules communicate with OSM with the help of REST API and sends the request to OSM five-time in case of any error or failure. After that, OSM REST API notifies the internet manager about the failure and the next process will be stopped immediately. Moreover, onboarding of all the descriptors are required for the instantiation of NST. The OSM uses these descriptors for the deployment of network slice template NST or network service. After onboarding all the descriptors, the policy configurator sends the specific service deployment request to the OSM. At the end, the required network service is deployed according to NST configurations. The architectural design of policy configurator for OSM is presented in our paper [38; 41].