Create an OpenFlow Network within a single PC

For more detail, visit http://www.openflowswitch.org/wk/index.php/OpenFlowVMS

1. Overview

When developing applications using OpenFlow, a small network of OpenFlow switches is often needed for testing and debugging. Using a simulated network for such development would be ideal, allowing more people to develop efficiently at their own pace. The OpenFlow Virtual Machine Simulation (OpenFlowVMS) package is developed to create that virtual simulated network in your very own desktop/laptop.

OpenFlowVMS is a set of Python scripts that create that virtual simulated network automatically, letting developers concentrate on their real tasks and not fight the details of setting up a testbed.

2. Description of an Example Network

3. Hardware Requirement

You will need a Linux PC. If you have Windows or Mac, you can use a virtual machine to run Linux on top of it. People have successfully used VMWare and VirtualBox. In the following, we assume you have Debian Linux (Lenny).

4. Setup Network

Step1: Install the dependencies

In Debian, run the following command

sudo apt-get install vde2 graphviz gv qemu genisoimage psmisc \
        debootstrap git git-core screen xterm python2.5 python-xml 

Step2: Download Software and Disk Images

Get OpenFlowVMS using git with

git clone git://openflowswitch.org/openflow-vms.git openflowvms

You will see the following directory/file structure.

openflowvms
 |- bin
      |- vms-*.sh
      |- vms-*.py
 |- pylib
      |-*.py
 |- samples
      |-*.xml
 |- xsd
      |-*.xsd

Make sure that

• openflowvms/pylib directory is in your PYTHONPATH
• openflowvms/bin directory is in your PATH

If you are sadly behind a firewall, try gitweb. More instructions for Git is available at the git page.

Then, download the following files:

File Name	Description	For OpenFlow v0.8.9	For OpenFlow v1.0
hda.dsk	disk image used for the hosts running on qemu	Download Link
kernel.bin	kernel image used for the hosts running on qemu	Download Link
ofdatapath.ko	openflow switch (kernel module); not supported from v1.0 and later	Download Link	Download Link
ofdatapath	openflow switch (userspace)
ofprotocol	openflow protocol module (used to communicate to the controller)
dpctl	openflow datapath control command

If you want to modify these files, you can create them by yourself. Please refer to OpenFlowVMS page.

Next, create the working directory for yourself and place the downloaded files as follows (the blue colored names are the downloaded files.)

<working directory>
 |- openflow.cd
      |- ofprotcol
      |- dpctl
      |- ofdatapath.ko  (not included in v1.0)
      |- ofdatapath 
 |- kernel.bin
 |- hda.dsk

Step3. Create Configuration File

Create network configuration file describing this topology. Let's start with the example configuration file, openflowvms/examples/2hosts-1ofsw.vms.xml, to create our own file.

 $ cp openflowvms/samples/2hosts-1ofsw.vms.xml  <working directory>/2hosts-2ofsw.vms.xml

The original file should look like this:

<network name="Simple Network">
  <of_mem>48</of_mem>

  <openflowswitch name="of1">
  </openflowswitch>

  <host name="host1">
    <ip><dynamic/></ip>
  </host>
  <host name="host2">
    <ip><dynamic/></ip>
  </host>

  <link end1="of1" end2="host1" />
  <link end1="of1" end2="host2" />
</network>

We modify it to the following (the modified part is highlighted by red)

<network name="Simple Network">
  <of_mem>48</of_mem>

  <openflowswitch name="of1">
 <!--To let spawn an xterm-->       
 <xterm>true</xterm>    
  </openflowswitch>

  <openflowswitch name="of2">  
   <xterm>true</xterm>  
  </openflowswitch> 

  <host name="host1">
    <xterm>true</xterm> 
    <ip><static>192.168.100.1</static></ip> 
  </host>
  <host name="host2">
    <xterm>true</xterm> 
    <ip><static>192.168.100.2</static></ip> 
  </host>

  <link end1="of1" end2="host1" />
  <link end1="of1" end2="of2" /> 
  <link end1="of2" end2="host2" />
</network>

Step4. Verify Configuration File

There are a few ways to check the validity of the configuration we have created above. It is a good practice to validate your network, before running it (you can skip this step if you're confident with the correctness of your configuration file).

To verify the xml file

We can check the validity of our configuration by verifying it against its schema definition.

 $xmlstarlet val -e -s openflowvms/xsd/vms.xsd <working directory>/2hosts-2ofsw.vms.xml

Errors will be listed if any, else the file will be declared as valid.

To verify the network topology

Also, we can draw the network and see if it is what we have intended.

 $ vms-draw.py 2hosts-2ofsw.vms.xml

5. Setup Controller

Please refer to the Controller Setup Section for multiple PCs/NetFPGA setup. Please make sure you run your controller on port 6633. Also, you need to match OpenFlow protocol version with switches and the controller. If you use OpenFlow v0.8.9 switches, which talks wiring protocol 0x97, you need a controller compiled with OpenFlow v0.8.9. If you use OpenFlow v1.0 switches, which talk wiring protocol 0x01, you need a controller compiled with OpenFlow v1.0. The above link has an explanation how to compile each version.

6. Run/Stop

To run your network, you will now run the following commands:

For kernel space switch (for v0.8.9 only) :

vms-start.py 2hosts-2ofsw.vms.xml

For user space switch (for v1.0 and for v0.8.9 if you prefer user space switch) , "-u" option is needed:

vms-start.py -u 2hosts-2ofsw.vms.xml

Note that files and directories needed for the setup will be checked for in the script.

Note that the vde directory generated contains the UNIX sockets through which you can control the VDE switches and wirefilters. Hosts and OpenFlow switches are run in qemu virtual machines, using screen.

Viola! Your very own OpenFlow network! All you have to do is to have your OpenFlow controller running at localhost port 6633.

To stop simulated network, there are two ways. The recommended way is to run

./<your network name>-stop.sh

which is generated when you run vms-start.py (<your network name> is "2hosts-2ofsw" in this case). The other "violent" method is to kill all the networks at one go using

vms-start.py -k

7. Basic Testing

On the controller PC, first check the switches are connected to the controller. You can check this by

$ netstat -n | grep 6633

To login to the host1, run the following command (both login name and password are "root").

$ screen -r host1

Similarly, to login to the of1 (openflow switch), run the following command:

$ screen -r of1

On the host1, run ping to check the the reachability to host2.

# ping 192.168.100.2

On each openflow switch, you can run the following command to see the flow table is actually installed.

# cd /cdrom
# ./dpctl dump-flows nl:0