**1. Introduction**

The continuous growth in the number of large‐scale datacenters (DC) poses new challenges to the capacity and elasticity of current optical network. Datacenter applications, such as sched‐ uled high‐speed data replication, require the substrate network to provide ultra‐high band‐ width dynamically [1]. This is quite different from the service model of traditional optical

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network, which arises the need for that the datacenter network (DCN) architecture to be rede‐ signed [2]. Recently, elastic optical network (EON) with software‐defined networking (SDN) architecture has been introduced into datacenters to improve the performance of service pro‐ visioning. This can jointly consider both IT resources and network resources and enable net‐ work to be programmed like general hardware [3–5]. The optical network integrated with SDN, namely software‐defined optical network (SDON), can provide high bandwidth with IT resources for multiple tenants [6]. It separates the control plane from the data plane and turns the control manner into a centralized and flexible one. In addition, it enables datacenter opera‐ tors to control and program network functions such as bandwidth provisioning with Quality of service (QoS) guarantees. Resources of datacenter are provisioned by virtualizing resources of distributed datacenters and operator's optical network in a coordinating manner [7]. A hier‐ archical control mechanism is proposed to control multi‐domain optical network [8], which can support connections between datacenters in multi‐domain scenario. On the basis of above studies, the objective of this chapter is to find what applications can be deployed on SDON.
