1 Software Defined Optical Networks (SDONs): A Comprehensive Survey Akhilesh Thyagaturu, Anu Mercian, Michael P. McGarry, Martin Reisslein, and Wolfgang Kellerer Abstract—The emerging Software Defined Networking (SDN) The SDN abstraction layering consists of three generally paradigm separates the data plane from the control plane and accepted layers [5] inspired by computing systems, from the centralizes network control in an SDN controller. Applications bottom layer to the top layer: (i) the infrastructure layer, (ii) interact with controllers to implement network services, such as network transport with Quality of Service (QoS). SDN facilitates the control layer, and (iii) the application layer, as illustrated the virtualization of network functions so that multiple virtual in Fig. 1. The interface between the application layer and networks can operate over a given installed physical network the control layer is referred to as the NorthBound Interface infrastructure. Due to the specific characteristics of optical (pho- (NBI), while the interface between the control layer and the tonic) communication components and the high optical transmis- infrastructure layer is referred to as the SouthBound Interface sion capacities, SDN based optical networking poses particular challenges, but holds also great potential. In this article, we (SBI). There are a variety of standards emerging for these comprehensively survey studies that examine the SDN paradigm interfaces, e.g., the OpenFlow protocol [7] for the SBI. in optical networks; in brief, we survey the area of Software The application layer is modeled after software applica- Defined Optical Networks (SDONs). We mainly organize the tions that utilize computing resources to complete tasks. The SDON studies into studies focused on the infrastructure layer, control layer is modeled after a computer’s Operating System the control layer, and the application layer. Moreover, we cover SDON studies focused on network virtualization, as well as (OS) that manages computer resources (e.g., processors and SDON studies focused on the orchestration of multilayer and memory), provides an abstraction layer to simplify interfacing multidomain networking. Based on the survey, we identify open with the computer’s devices, and provides a common set of challenges for SDONs and outline future directions. services that all applications can leverage. Device drivers in Index Terms—Control layer, infrastructure layer, optical net- a computer’s OS hide the details of interfacing with many work, orchestration, Software Defined Networking (SDN), virtual different devices from the applications by offering a simple network. and unified interface for various device types. In the SDN model both the unified SBI as well as the control layer I. INTRODUCTION functionality provide the equivalent of a device driver for interfacing with devices in the infrastructure layer, e.g., packet At least a decade ago [1] it was recognized that new network switches. abstraction layers for network control functions needed to Optical networks play an important role in our modern in- be developed to both simplify and automate network man- formation technology due to their high transmission capacities. agement. Software Defined Networking (SDN) [2]–[4] is the At the same time, the specific optical (photonic) transmission design principle that emerged to structure the development of and switching characteristics, such as circuit, burst, and packet those new abstraction layers. Fundamentally, SDN is defined switching on wavelength channels, pose challenges for con- by three architectural principles [5], [6]: (i) the separation trolling optical networks. This article presents a comprehen- of control plane functions and data plane functions, (ii) the sive survey of Software Defined Optical Networks (SDONs). logical centralization of control, and (iii) programmability of SDONs seek to leverage the flexibility of SDN control for arXiv:1511.04376v3 [cs.NI] 17 Jul 2016 network functions. The first two architectural principles are supporting networking applications with an underlying optical related in that they combine to allow for network control network infrastructure. This survey comprehensively covers functions to have a wider perspective on the network. The idea SDN related mechanisms that have been studied to date for is that networks can be made easier to manage (i.e., control optical networks. and monitor) with a move away from significantly distributed control. A tradeoff is then considered that balances ease of management arising from control centralization and scalability A. Related Work issues that naturally arise from that centralization. The general principles of SDN have been extensively cov- Please direct correspondence to M. Reisslein ered in several surveys, see for instance, [2], [6], [7], [10]– A. Thyagaturu, A. Mercian, and M. Reisslein are with the School of [27]. SDN security has been surveyed in [28], [29], while Electrical, Computer, and Energy Eng., Arizona State University, Tempe, management of SDN networks has been surveyed in [26] and AZ 85287-5706, USA, Phone: 480-965-8593, Fax: 480-965-8325, (e-mail: fathyagat, amercian, [email protected]). SDN-based satellite networking is considered in [30]. M. McGarry is with the Dept. of Electr. and Comp. Eng., University of To date, there have been relatively few overview and sur- Texas at El Paso, El Paso, TX 79968, USA (email: [email protected]). vey articles on SDONs. Zhang et al. [31] have presented W. Kellerer is with the Lehrstuhl fur¨ Kommunikationsnetze, Tech- nische Universitat¨ Munchen,¨ Munich, 80290, Germany, (email: wolf- a thorough survey on flexible optical networking based on [email protected]). Orthogonal Frequency Division Multiplexing (OFDM) in core 2 SDN network domain SDN network domain Non- SDN Application Layer network domain Application Layer, Sec. VI E.g., Recovery, Topology Discov. APPLICATION Northbound Interface (NBI) Northbound Interface (NBI) CONTROL FORWARDING BASE Control Layer Control Layer, Sec. IV E.g., Exterior Gateways E.g., Open Netw. Operat. Sys. (ONOS) with Border Gateway Protocol (BGP), Southbound Interface (SBI) Southbound Interface (SBI) Interior Gateways with Open Shortest Path First Infrastructure Layer Eastbound (EBI) Interface (OSPF) Protocol. Infrastructure Layer, Sec. III Westbound (WBI) Interface E.g., OF-Switch, NETCONF Device Fig. 1. Illustration of Software Defined Networking (SDN) abstraction layers: The infrastructure layer implements the data plane, e.g., with OpenFlow (OF) switches [7] or network elements (devices) controlled with the NETCONF protocol [8]. A controller at the control layer, e.g., the ONOS controller [9], controls the infrastructure layer based on the application layer requirements. The interface between the application and control layers is commonly referred to as the NorthBound Interface (NBI), while the interface between the control and infrastructure layers is commonly referred to as the SouthBound Interface (SBI). The WestBound Interface (WBI) interconnects multiple SDN domains, while the EastBound Interface (EBI) interconnects with non-SDN domains. (backbone) networks. The survey briefly notes how OFDM- Kerpez et al. [38]. based elastic networking can facilitate network virtualization Bitar [39] has surveyed use cases for SDN controlled broad- and surveys a few studies on OFDM-based network virtual- band access, such as on-demand bandwidth boost, dynamic ization in core networks. service re-provisioning, as well as value-added services and Bhaumik et al. [32] have presented an overview of SDN service protection. Bitar [39] has discussed the commercial and network virtualization concepts and outlined principles perspective of the access networks that are enhanced with SDN for extending SDN and network virtualization concepts to the to add cost-value to the network operation. Almeida Amazonas field of optical networking. Their focus has been mainly on et al. [40] have surveyed the key issues of incorporating industry efforts, reviewing white papers on SDN strategies SDN in optical and wireless access networks. They briefly from leading networking companies, such as Cisco, Juniper, outlined the obstacles posed by the different specific physical Hewlett-Packard, Alcatel-Lucent, and Huawei. A few selected characteristics of optical and wireless access networks. academic research projects on general SDN optical networks, Although our focus is on optical networks, for completeness namely projects reported in the journal articles [33], [34] and we note that for the field of wireless and mobile networks, a few related conference papers, have also been reviewed SDN based networking mechanisms have been surveyed by Bhaumik et al. [32]. In contrast to Bhaumik et al. [32], in [41]–[47] while network virtualization has been surveyed we provide a comprehensive up-to-date review of academic in [48] for general wireless networks and in [49] for wireless research on SDONs. Whereas Bhaumik et al. [32] presented sensor networks. SDN and virtualization strategies for LTE a small sampling of SDON research organized by research wireless cellular networks have been surveyed in [50]. SDN- projects, we present a comprehensive SDON survey that is based 5G wireless network developments for mobile networks organized according to the SDN infrastructure, control, and have been outlined in [51]–[54]. application layer architecture. For the SDON sub-domain of access networks, Cvijetic [35] has given an overview of access network challenges