Huawei Lancaster University France Telecom China Telecom Telefonica Previously transport networks were typically static, lacked flexibility, and required long planning times when deploying new services. Network Providers and Service Providers have embraced technologies that allow separation of data plane and control plane, distributed signaling for path setup and protection, and centralized path computation for service planning and traffic engineering. Although these technologies provide significant benefits, they do not meet the growing need for network programmability, automation, resource sharing, and service elasticity necessary for meeting operator's requirement for their virtual network operation. Virtual network operation refers to the creation of a virtualized environment allowing operators to view the abstraction of the underlying multi-admin, multi-vendor, multi- technology networks and to operate, control and manage these multiple networks as if a single virtualized network. Another dimension of virtual network operation is associated with use of the common core transport network resource by multi-tenant service networks as a way of providing a virtualized infrastructure to flexibly offer new services and applications. The work effort investigating this problem space is known as Abstraction and Control of Transport Networks (ACTN). This document provides an ACTN problem description, scope of work, and outlines the core requirements to facilitate virtual network operation.