Ryu - Installation

- Ryu is a SDN controller platform which supports OpenFlow. See also: http://osrg.github.io/ryu/

- By https://github.com/mininet/openflow-tutorial/wiki/Create-a-Learning-Switch#Controller_Choice_Ryu_Python, python-gevent, python-routes, python-webob, and python-paramiko should be installed.

• "sudo apt-get update" - update Lunix update packages
• "sudo apt-get install python-pip", "sudo apt-get install python-dev" - install python packages if not yet
• Similarly, install python-gevent, python-routes, python-webob, and python-paramiko.
• I see that somebody also installed python-eventlet, so I just install them in case of need.
• Install RYU: "sudo pip install ryu"
• Test:

mininet@mininet-vm:~$ ryu-manager 
loading app ryu.controller.ofp_handler
instantiating app ryu.controller.ofp_handler of OFPHandler

- Install Ryu GUI interface (optinal)

• "sudo git clone git://github.com/osrg/ryu.git" - download ryu source code
• "sudo pip install flask gevent-websocket" - install needed packages
• Download: https://github.com/yamada-h/ryu/archive/gui-patch-v3-rebase.zip
• Extrat the downloaded file and copy directory "ryu-gui-patch-v3-rebase/ryu/gui/" to "/home/[user]/ryu/ryu/"
• edit "/ryu/ryu/topology/switches.py", and comment these lines:

CONF.register_cli_opts([
    cfg.BoolOpt('observe-links', default=False,
                help='observe link discovery events.'),
    cfg.BoolOpt('install-lldp-flow', default=True,
                help='link discovery: explicitly install flow entry '
                     'to send lldp packet to controller'),
    cfg.BoolOpt('explicit-drop', default=True,
                help='link discovery: explicitly drop lldp packet in')
])

• Start Ryu: "ryu-manager --verbose --observe-links ryu.app.simple_switch ryu.app.rest_topology  ryu.app.ofctl_rest ryu.topology.switches"
• ryu.app.simple_switch: a simple learning switch which supports OpenFlow 1.0,  ryu.app.simple_switch_13 supports OpenFlow 1.3
• The rest are for GUI
• Start controller:"./ryu/ryu/gui/controller.py" and connect to "127.0.0.1:8000" to see the topology
• Note that the name of switches seems matter when you want to see it in the topology. For example, in my fat tree topology, I tried to set switches' names as their IP. If I set a switch name as "10_0_0_1", it doesn't work; but if set as "10001" it did work! Amazing! 
• Enable STP will also eliminate some links.
• See an example: http://dj184dja8.blogspot.tw/2016/04/ryu-mininet-sample-k4-fat-tree.html
• If you confront an import error indicating there is no views.websocket module, please refer to http://dj184dja8.blogspot.tw/2016/05/ryu-gui-installation-problem.html