Software Defined Network

Definition
A Software Defined Network (SDN) is

"[a] private line service that integrates use of AT&T's Message Telecommunications Service switched network and customized, computerized network features to create a private line network for customers. Customers identify the specific points they wish to connect via SDN service and have a specific numbering plan to call these locations. SDN also allows customers to call points off its network by dialing a single digit for off-network access. SDN customers receive access to this service via (1) their own facilities, (2) special access service, or (3) a new type of switched access developed for SDN and referred to as "standard switched access.""