Attack on SDN

It is no longer an OSI seven-layer model, but a brand-new SDN three-layer model .
It originated from Ethane, a project led by a doctoral student at Stanford University: through a centralized controller (NOX), network administrators can define network flow-based control policies, and use this policy on network devices to control the entire network. .
Openflow switches do not have separate CPUs. All path calculation, security policy and other functions are implemented by the controller. Then it is sent to the switch through the Openflow protocol. The switch forwards through the flow table (Flow Table).
Control forwarding is completely separated and programmable (change the script of the controller, you can change the network).

The concept of NFV was proposed by network operators.
Many functions in the real network (firewall, load balancing, etc.) are implemented by dedicated hardware (the functions cannot be changed after death).
Dedicated hardware has the problems of function solidification, difficult deployment, and high cost.
So the operator proposes to integrate the above functions into a general server . These functions are implemented through software . (May be to open several virtual machines, each responsible for the realization of some functions), to achieve programmability .
SDN also hopes to convert these hardware devices into software plug-ins deployed in the controller. One brain can solve all problems, the following is only responsible for forwarding.

Forwarding layer: In a narrow sense, it is a bunch of switches. Broadly speaking, devices that support the Openflow protocol can be said to be Openflow devices. There is no strict distinction between routers and switches in SDN, as long as they support the Openflow protocol.
Control layer: The server where the controller is installed (the controller is software!).
Application Layer: Scripts or written functions.
For example, if you want to make a device in the forwarding layer a hub. Write a Python script here at the application layer, and then run the script in the controller. At this time, the controller sends the flow table to the forwarding layer through the Openflow protocol, which realizes the function of the hub. (If you want to achieve other functions, you can change the script to achieve software and programmable features! )

In the past, the device was controlled by a specific language or command line of the device. In SDN, Python or Java script is used to implement functions at the application layer.