Nowadays, there are several different controllers to be used in Software Defined Networking(SDN). Compare with the OpenDaylight and ONOS, Ryu is a much lighter controller and its control way is very clear. In addition, Ryu is also a good tool for students to do SDN experiments and it is very suit for beginners. However, Ryu still have its defects such as Ryu only supporting single controller. Therefore, if the only controller have some uncoverable problems, the networking will collapse.

如今，SDN有很多不同种类的控制器。 相较于OpenDaylight和ONOS而言，Ryu是一个非常轻量级的控制器，并且它的控制方式非常简洁。 此外，Ryu同样也是一个非常适合学生进行SDN相关实验，并且它非常适合初学者的学习。 然而，Ryu同样有着它自身的缺陷，例如Ryu只支持单个控制器，这也意味着当这个单个控制器在遭受到不可逆的问题时，整个网络都可能会塌陷。

install Ryu

安装Ryu

Set vlan

设定vlan

shortest path in Data Center

基于数据中心的最短路径

Yen's Algorithm

Yen算法的实现