Ryu originates from a Japanese word meaning flow. It is a component-based, open source SDN framework fully written in Python that provides a precise software component and comprehensive API essential for the development of network applications for control and management.

Ryu supports various protocols for managing network devices, such as OpenFlow, Network Configuration Protocol (NETCONF), and the OpenFlow Management and Configuration Protocol (OF-Config), Open vSwitch Database (OVSDB) management protocol. It currently supports OpenFlow versions 1.0, 1.2, 1.3, 1.4, and 1.5 and Nicira extensions. NTT labs currently supports the Ryu controller, and it is also deployed across its various cloud data centers.