1.过去20年中可编程网络的发展可以分为几个阶段？每个阶段的贡献是什么？
(1) active networks
• introduced programmable functions in the network to enable greater to innovation;
• Programmable functions in the network to lower the barrier to innovation;
• Network virtualization, and the ability to demultiplex to software programs based on packet headers；;
• The vision of a unified architecture for middlebox orchestration.
(2) control and data plane separation
• developed open interfaces between the control and data planes;
• Logically centralized control using an open interface to the data plane;
• Distributed state management;
(3) the OpenFlow API and network operating systems
• represented the first instance of widespread adoption of an open interface and developed ways to make control-data plane separation scalable and practical.
• Generalizing network devices and functions
• The vision of a network operating system
• Distributed state management techniques
2.网络虚拟化与SDN的关系？
• represented the first instance of widespread adoption of an open interface and developed ways to make control-data plane separation scalable and practical.
• Generalizing network devices and functions
• The vision of a network operating system
• Distributed state management techniques