# Scalable OneM2M IoT Open-Source Platform Evaluated in an SDN Optical Network Controller Scenario +
## 3 The OneM2M IoT Platform and Proposed Implementation for Optical Network Control
### The Motivation for an OneM2M-Based SDN Optical Controller  
Optical networks currently employ a number of SDN controllers not specifically designed for high scalability performance. However, the transition from legacy optical networks to open and disaggregated paradigms poses the challenge to employ control elements with improved scalability for several reasons. Firstly, the number of different nodes is increasing (e.g., a single optical node is now split into the open ROADM device, the OLS device and the xPonders devices, each one exposing a different SDN agent model). Secondly, disaggregation requires more flexible and automatic commissioning and decommissioning procedures for disaggregated components. Finally, differently from legacy and old GMPLS-enabled agents, disaggregation requires handling different device abstractions (i.e., YANG models) and the related southbound APIs. IoT controllers can properly address these novel requirements in terms of the number and type of devices. Moreover, their internal design is compatible with the implementation of match-action flow rules, as required by the SDN paradigm.  
The SDN Controller is the control-plane entity in charge of controlling all the network devices in the data plane. From this perspective, two are the key features of an SDN controller: the capability to perform the configuration of the traversed devices (according to the forwarding/routing decisions) and the capability to monitor, in real-time, the main parameters of all the devices (to maintain both the up-to-date network topology view and the state-full dataset of the configured connections). When considering optical networks, each device includes many parameters to be maintained (i.e., the input and output power levels of all the optical lines, the coherent parameters of each transponder port, the configuration/state of each amplifier). When the number of devices and the number of parameters grow, it is convenient to adopt distributed platforms, where configuration and monitoring functions are decoupled. From one side, the distributed approach improves the system efficiency and performance, reducing the possibility of overloading the SDN controller. From the other side, it can lead to continuous interaction among the configuration and monitoring platforms with the loss of fundamental pieces of information. The idea to adopt an IoT platform to control the optical network has been considered by exploring alternative solutions. The key functionalities of the SDN Controller perfectly fit with the basic capabilities of such a platform. By considering the optical devices as sensors, there is the possibility to send specific messages to the nodes (i.e., send configuration messages that include the full view of a node). The reception of periodic updates allows maintaining an outlook of the entire network topology and the state of the connections. For the optical network nodes, specific representation/abstraction models must be considered (i.e., OpenConfig or OpenROADM).  
Figure 1: The OneM2M resource structure.