As a closing post on this effort I present you the following contributions:
Poxy: A proxy for the OpenFlow controller – OpenFlow switch connection
Pongo: An POX application, integrated with Django, which allows handling of the topology of a mesh of nodes (currently customized for the Community-Lab testbed).
My thesis titled “Software Deﬁned Networking for Community Network Testbeds” can be found here.
A paper titled “Software Deﬁned Networking for Community Network Testbeds” in the 2nd International Workshop on Community Networks and Bottom-up-Broadband(CNBuB 2013).
Here you can find the presentation slides.
Thanks for following. Comming up more work about Community Networks.
Instructions mostly from the Open vSwitch Readme
// Delete all linux bridges that exist. // then remove the bridge module root@debian:/# modprobe -r bridge // Install common and switch packages root@debian:/# aptitude install openvswitch-switch openvswitch-common // Install and build the ovs module using the DKMS package root@debian:/# aptitude install openvswitch-datapath-dkms
// Load the ovs module root@debian:/# modprobe openvswitch_mod // Create the configuration database root@debian:/# ovsdb-tool create /var/lib/openvswitch/conf.db /usr/share/openvswitch/vswitch.ovsschema // Start ovsdb-server without SSL support root@debian:/# ovsdb-server --remote=punix:/var/run/openvswitch/db.sock --remote=db:Open_vSwitch,manager_options --pidfile --detach // The next command should be run the firt time a database is created // with the ovsdb-tool as we did above. It initializes the db root@debian:/# ovs-vsctl --no-wait init // Start ovs daemon root@debian:/# ovs-vswitchd --pidfile --detach // Create a bridge root@debian:/# ovs-vsctl add-br br0
And we are ready to go!
Integrate POX with OVS
// Get Pox and move to the betta -current stable branch - user@debian:~/$ git clone http://www.github.com/noxrepo/pox user@debian:~/$ cd pox/ user@debian:~/pox/$ git checkout betta // Start an empty controller, without templates where rules have to // be added manually user@debian:~/pox/$ ./pox.py samples.pretty_log // Go in another terminal // Define the switch's policy if connection with the server is lost // standalone or secure, see ovs-vsctl manual root@debian:/# ovs-vsctl set-fail-mode ovs-switch standalone // Define the controller address to the switch root@debian:/# ovs-vsctl set-controller br0 tcp:0.0.0.0:6633
Now everything is set up. Have fun 😛
The topology used in the tutorial is the following (the controller is external to mininet):
We start the Openflow reference controller with the command:
$ controller ptcp:
This will create the following series of messages to be exchanged.
You can get a copy of a similar capture from here. The capture can be viewed in wireshark using the Openflow Wireshark dissector (Helpful guide).
Continuous communication problem.
Then, the controller and the switch continue exchanging frequently
Echo Request and
Echo Reply messages.
According the Openflow specification :
In the case that a switch loses contact with the controller, as a result of a echo request timeout, TLS session timeout, or other disconnection, it should attempt to contact one or more backup controllers.
This can prove to be a problem for our case. How this is implemented by the different controllers, as well as the frequence and its possible modification in a proactive environent should be explored. The tutorial mentions about
When an OpenFlow switch loses its connection to a controller, it will generally increase the period between which it attempts to contact the controller, up to a maximum of 15 seconds. Since the OpenFlow switch has not connected yet, this delay may be anything between 0 and 15 seconds. If this is too long to wait, the switch can be configured to wait no more than N seconds using the --max-backoff parameter.
Also useful is this post in the ovs-discuss list.
Since the switch flow tables are initially empty a ping command will cause the following message exchange.
You can get a copy of a similar capture from here.
We can see the
Packet Out and
Flow Mod messages.
Flow removal messages do not appear as mentioned in the tutorial. This may be a problem with the OVS version (1.2.2). Additionally, this version does not support the
send_flow_rem flow option in through the
ovs-ofctl tool and neither is this option supported by the
dpctl provided by the OF implementation. Thus, there is no way to check which is the actual problem.
User-space OVS vs kenel-space OVS
Following the tutorial we can see that using kernel-space OVS bandwith (measured with iperf) is arround 190 Mbps while with user-space OVS is arround 23Mbps.
Note: Mininet Internet Connection
By default, the mininet vm comes without connection to the host network. This happens because the guest network is implemented with the virtio paravirtualization driver.
There is going to be a post following, which will contain notes from the rest of the tutorial using POX controller in order to implement L2 and L3 learning.