[Ryu] unsupported version 0x1. If possible, set the switch to use one of the versions [4]

 這個錯誤的意思就是OpenFlow的版本有誤，解決方法就是要設定OVS支援OpenFlow
 

#mn --controller=remote,ip=CTR_IP --topo linear,2 --switch ovsk,protocols=OpenFlow13 
or
#ovs-vsctl set bridge s1 protocols=OpenFlow10,OpenFlow13
#ovs-vsctl set bridge s2 protocols=OpenFlow10,OpenFlow13

而如果執行 ovs-vsctl發以下訊息，那表示你的OVS版本太低了，必須更新OVS。
Bridge does not contain a column whose name matches "protocols"

更新方法：

#wget http://openvswitch.org/releases/openvswitch-2.3.1.tar.gz
#tar -zxvf openvswitch-2.3.1.tar.gz
#cd openvswitch-2.3.1
#./configure --prefix=/usr --with-linux=/lib/modules/`uname -r`/build
#make
#make install
#make modules_install
#rmmod openvswitch
#depmod -a
#/etc/init.d/openvswitch-switch restart

Reference:
[1] Upgrading Open vSwitch