虚拟，混合和SD-WAN该如何进行比较和对比

The following is a virtual, hybrid and SD-WAN comparison and contrast:

1. 虚拟：Virtual private networks (VPNs) provide secure, private connectivity over a shared public infrastructure such as the Internet. A VPN can be thought of as a "tunnel" that encrypts and encapsulates data as it travels from one point to another.

2. 混合：Hybrid networks combine the best of both worlds - the security and reliability of a private network with the flexibility and cost-effectiveness of a public network.

3. SD-WAN：Software-defined wide area networking (SD-WAN) is a type of WAN architecture that uses software-defined networking (SDN) principles to virtualize WAN connectivity and optimize network traffic flows.