# Emulating Software-Defined Disaggregated Optical Networks in a Containerized Framework
## 1 Introduction  
The rapid growth of Internet traffic that we are currently experiencing [1, 2] is based on the expansion of cloud services and the huge amount of traffic supported by the content delivery networks (CDNs) [1]. This clearly increases congestion issues in communication networks, with particular emphasis in the core and backbone segments [3]. Furthermore, the global crisis of COVID-19 has revealed the need for remote communications in both the social and business spheres [2, 4]. This crisis has become an incipient increase in video-call-related traffic through the use of applications such as Zoom [5], Microsoft Teams/Skype [6] or Cisco Webex [7]. Finally, these challenges are compounded by the need to meet the performance specifications for the fifth generation Internet (5G), where it is planned to obtain (a) a scalable management environment that enables the dynamic deployment of cloud-based applications, (b) a reduction of approximately 20% in operational costs and (c) total latency to the user of less than 1 ms [8]. The combination of all these challenges requires drastic changes in the way transport network resources are controlled and managed, moving away from traditional network management techniques. Under this umbrella, software defined networking (SDN) andnetwork function virtualization (NFV) emerge as key technologies to address the above challenges in an efficient way. In this work we will put the light on SDN. SDN is becoming a consolidated technology for network management that encompasses a set of techniques aimed at the management of networks that focus mainly on one basic principle: decoupling the decisions made at the control plane with respect to the actions taken at the data plane [9]. This principle allows unprecedented degrees of flexibility in the system, because the network switches and routers become simple forwarding devices that send and receive traffic, while the logical control of the network can easily be centralized on an external controller [10]. Conversely to traditional vendor-locked communication networks, SDN technology brings to network operators, among other benefits, the capability to: respond to challenges (such as big traffic fluctuations due to major sport or public events), operate their network in a cost-effective manner, evolve the network infrastructure, foster innovative solutions [10]. Relevant for optical networks, SDN is a powerful enabler to control and manage the wide variety of network elements with particular photonic transmission and switching characteristics inherent of the optical domain [11]. In this context, software-defined optical networks (SDONs) aim to exploit the flexibility of SDN control to support network applications with an underlying optical network infrastructure [12]. Within SDON, software models dedicated to the characterisation of optical elements, devices and systems are of utmost significance to enable the creation of _software agents_. In this regard, an agent is assumed to be a light-weight software that translates the necessary commands to permit communication between the SDN controller and the optical device placed in the optical data plane. Consequently, agents play a relevant role in disaggregated optical networks. Horizontal disaggregation in optical network is aimed at decomposing the optical data in its single components [13]. Disaggregated optical networks (DONs) leverage this idea to be presented as a new technology in optical networks and brings synergies with the SDN paradigm. Under this umbrella, several cooperative projects, such as Open Config [14], Open ROADM [15] or Telecom Infra Project [16], have been arising for the last years, with the target of providing unified models of optical devices. Thus, allowing the deployment of complex optical network architectures through the use of vendor-independent devices. This fact is remarkable because it avoids one of the most challenging traditional issues in optical network implementations, the vendor islands.