Tools used with Opendaylight

To test Opendaylight and the applications written on Opendaylight, we need to use a bunch of tools. This blog covers some of the tools that I have used. The tools covered are Mininet, dpctl, Wireshark, Packeth, Postman.

Mininet:

Mininet creates a realistic virtual network that can be programmed using controller. Data flows can be programmed using Openflow. Mininet internally contains a vswitch which can be programmed with OVSDB. Opendaylight Hydrogen release introduces ovsdb plugin through which Opendaylight can control any vswitch. Mininet can either be run in a separate VM or can be installed in the same VM as Controller. I have tried both options and they work fine. Image for both options can be downloaded from Mininet website (http://mininet.org/download/) Installing Mininet: I followed steps below to install Mininet in my Ubuntu 12.04:

sudo apt-get install -y mininet/precise-backports
 
sudo service openvswitch-controller stop
sudo update-rc.d openvswitch-controller disable

sudo apt-get install -y linux-headers-`uname -r`
sudo dpkg-reconfigure openvswitch-datapath-dkms
sudo service openflow-switch restart

By default, Mininet installed Openvswitch version 1.4.0. I upgraded Openvswitch using the procedure described here. Following were the exact steps I followed to upgrade Openvswitch to 2.1.0. Download specific version of Openvswitch from here.

cd 
./configure --prefix=/usr --with-linux=/lib/modules/`uname -r`/build
make
sudo make install
sudo make modules_install
sudo rmmod openvswitch
sudo depmod -a
sudo /etc/init.d/openvswitch-controller stop
sudo update-rc.d openvswitch-controller disable
sudo /etc/init.d/openvswitch-switch start

Creating different topologies: Mininet comes with some standard topologies like linear, tree and can be specified from command line. Simple pre-built topology creation: Example below creates a tree topology with 2 levels sudo mn --controller=remote,ip=192.168.56.101 --topo tree,2 Creating custom topologies: Custom topologies can be specified using a python script and using custom option with mininet. Following example creates a 3 switch triangle topology with 1 host to each switch: sudo mn --custom ~/mininet/custom/triangle_top.py --topo=mytopo --controller=remote,ip=192.168.56.101,port=6633 triangle_top.py:

class MyTopo( Topo ):
    "Simple topology example."

    def __init__( self ):
        "Create custom topo."

        # Initialize topology
        Topo.__init__( self )

        # Add hosts and switches
        h1 = self.addHost( 'h1' )
        h2 = self.addHost( 'h2' )
        h3 = self.addHost( 'h3' )
        s1 = self.addSwitch( 's1' )
        s2 = self.addSwitch( 's2' )
        s3 = self.addSwitch( 's3' )

        # Add links
        self.addLink( s1, s2)
        self.addLink( s1, s3)
        self.addLink( s1, h1)
        self.addLink( s2, h2)
        self.addLink( s3, h3)

topos = { 'mytopo': ( lambda: MyTopo() ) }

In the above example, 3 hosts and 3 switches are created initially. Then links are created between the switches and hosts. When this topology is discovered by Opendaylight, following topology is displayed in the Controller view. Complex Mininet example: Following example creates a custom topology with custom link characteristics(bandwidth, delay), custom mac address for switches and custom ip address for the hosts. sudo mn --custom ~/Downloads/mininet/custom/multi_path1.py --topo=mytopo --pre ~/Downloads/mininet/pre/host3_diff_subnet.py --host=rt --link=tc --mac --controller=remote,ip=192.168.56.101,port=6633 –pre: script to run before tests, can be used to specify parameters like custom ip address for the hosts in the –pre option, we can set ip like: h1 ifconfig h1-eth0 10.0.1.1/24 –post: CLI script to run after tests can be used for cleanup –mac: Custom mac address starting with 00:00:00:00:00:01 for switches use –host and –link option and specify link parameters in addlink in the custom topology python script. self.addLink( s1, s2, bw=10, delay='5ms', max_queue_size=1000) Specifying link parameters becomes useful when we need to create applications which use the link parameters and makes dynamic decisions. Other Mininet options: From mininet prompt, there are bunch of commands available which can be seen with “mininet -h” ======================================== EOF exit intfs link noecho pingpair py source xterm dpctl gterm iperf net pingall pingpairfull quit time dump help iperfudp nodes pingallfull px sh x ======================================== Useful ones being: link, nodes – to see nodes and switches pingall – ping test between hosts iperf, iperfudp – performance test between hosts

dpctl:

dpctl is a command-line tool for monitoring and administering openflow data paths. Examples: Display properties of a switch: dpctl show tcp:127.0.0.1:6634 For switch 2, use port number 6635 and so on. Dumping and deleting flows: dpctl dump-flows tcp:127.0.0.1:6634 dpctl del-flows tcp:127.0.0.1:6634

Wireshark:

To monitor packets. Packets can be monitored on each of the virtual interfaces created in Mininet. To monitor openflow packets, openflow plugin needs to be installed for Wireshark.

Packeth:

Useful for custom packet generation. Packets can be generated on each of the virtual interfaces created in Mininet. Can be downloaded from http://packeth.sourceforge.net.

Postman:

Postman is a powerful web-based REST api client. Its very useful to try out the northbound REST apis exposed by Opendaylight. Postman can be installed in Chrome browser. References:

• Mininet Walkthru
• Mininet Openflow tutorial
• Postman REST api client
• Openflow tutorial from Brent