This is my first OpenFlow controller, wrote for the CATR (for testing). Also, this is an experimental project for Wang jian, kimi Yang and me. Our goals are:

· Add ovsdb-management protocol into the controller (like a driver)
· Make module/app that can be removed on the fly
· And everything we would come up with

So, instead of performance (not able to do so), we focus on the functionality of a controller. Below is the structure of this document:

 CATR Controller -+- Architecture -+- Overall  
                  |                |  
                  |                +- Step by step -+- Tornado & Echo Server  
                  |                                 |  
                  |                                 +- Scapy & OpenFlow lib  
                  +- Detailed Design -+- TCP Server  
                  |                   |  
                  |                   +- OpenFlow Library  
                  |                   |  
                  |                   +- Event System  
                  +- Idea List  

###Overall The CATR Controller is first started as a testing tool for the OpenFlow cricuit extension project in CATR of MIIT.
This is a pic of current architecture:

It has three layers. The bottom one is the TCP Server, handling TCP connections started from OpenFlow Switches.
The second one is a Openflow library which will parse upcomming messages and pack message to switches. And the third layer is processing logic.

###Step by step As shown in the previous picture. The bottom of CATR Controller is a TCP server using IOLoop in tornado.