The emerging Software Defined Networking (SDN) paradigm separates the data plane from the control plane and centralizes network control in an SDN controller. Applications interact with controllers to implement network services, such as network transport with Quality of Service (QoS). SDN facilitates the virtualization of network functions so that multiple virtual networks can operate over a given installed physical network infrastructure. Due to the specific characteristics of optical (photonic) communication components and the high optical transmission capacities, SDN based optical networking poses particular challenges, but holds also great potential. In this article, we comprehensively survey studies that examine the SDN paradigm in optical networks; in brief, we survey the area of Software Defined Optical Networks (SDONs). We mainly organize the SDON studies into studies focused on the infrastructure layer, the control layer, and the application layer. Moreover, we cover SDON studies focused on network virtualization, as well as SDON studies focused on the orchestration of multilayer and multidomain networking. Based on the survey, we identify open challenges for SDONs and outline future directions

Abstract-Multi-thread polling (MTP) with offline scheduling and offline excess bandwidth distribution has recently been proposed to overcome the long propagation delay of long-reach passive optical networks (LR-PONs). In this paper, we propose a complementary MTP approach with online scheduling and online excess bandwidth distribution. We evaluate the throughput-delay performance of offline and online MTP against offline and online singlethread polling (STP) with excess bandwidth distribution as well as double-phase polling (DPP) with excess bandwidth distribution. We find that online MTP and STP as well as DPP give significantly lower average packet delays than offline MTP.Index Terms-Delay evaluation, dynamic bandwidth allocation, excess bandwidth distribution, long-reach PON (LR-PON), multithread polling (MTP).

Globally distributed scientific experiments usually involve massive data volumes and distributed data analysis being done by many collaborators. With complex workloads and heterogeneous resources, each user may require certain characteristics for their network paths. In this paper, we present the iNDIRA tool, which interacts with SDN northbound interfaces to enable intent-based networking. It provides reliable, simple, and technology-agnostic communication between users and networks. Focusing particularly on science applications, iNDIRA uses natural language processing to construct semantic RDF graphs to understand, interact, and create the required network services. The technical challenges addressed by iNDIRA are: (1) development of a high-level descriptive language to query for network-application requirements, (2) keyword identification and condition checking based on user profiles and topology details, (3) allow user negotiation based on the current network state, (4) provide network provisioning guidance, and finally, (5) automatically provision and monitor a layer-2 network path for use by the application. iNDIRA is implemented on the ESnet network, where it interacts with OpenNSA (aka the NSI client) and Globus data transfer tools, to build complex cross-domain network paths for heterogeneous science applications and perform secure data transfer. We describe our implementation of iNDIRA running on ESnet's production network. We present results of iNDIRA's query processing mechanism, evaluate iNDIRA's intent language evaluation with other approaches, and describe future enhancements for iNDIRA.

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