The session presents representatives of vendors (ECI, Infinera), research and education network operators (GEANT/Εuropean NRENs) as well as an EC-funded research and innovation project (ACINO EU) delving into the importance of software-defined multilayer networks. Traditionally, telecommunications as well as R&E networks have been planned, deployed, and controlled, one layer at a time. Starting at the services layer, such as for data, video, voice, or mobile, each service determined its network-facing requirements based on projected demand. These requirements served as inputs to various transport layers for amalgamating and handling different traffic types, which in turn served as inputs for an underlying optical layer. Each layer was planned and deployed individually, often using unique equipment, to meet expected levels of availability. This layer-at-a-time approach, however, no longer serves the best interests of communications service providers, who are being pressured by alternative cloud-based OTT managed services, and heightened customer expectations for service-on-demand. An equivalent pressure applies to R&E networks, where diverse traffic demands (including big science data flows) and cost reduction requirements demand for a more efficient use of the available resources. Planning the layers separately produces an overall expensive solution. Moreover, individual layer control – with lengthy cycles for understanding the effects on other layers – is very cumbersome for responding rapidly to shifts in demand. Multilayer optimization addresses these challenges by looking at all network layers simultaneously. Software defined networking provides the means to introduce efficient multilayer operations. The proposed session will provide to the individual speakers the opportunity to present the different aspects and challenges of multilayer optimization utilizing SDN.