Welcome to the OpenFlow-1.3 Tutorial!
This tutorial is inspired by the old OpenFlow 1.0 Tutorial and is a basic guide to start a practical experience with the OpenFlow 1.3 version.
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At the end you should be able to:
Pre-Requisites
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In order to be able to go through this tutorial you will need the following development tools for OpenFlow.
Scriptflow 1.3 YearsThe shortest path..
Mininet now has options to install the OpenFlow 1.3 software switch and NOX.
The commands above will install Mininet,the software switch, NOX and Wireshark in only one shot!You still need to install the OpenFlow 1.3 plugin for wireshark.
And that's it! But, if you prefer to install all of them separately, follow the steps below.
The (not so) long road
In this part we show how to setup the tools required for this tutorial. For more details please check their documentation.
OpenFlow 1.3 Software switch
Install Netbee dependencies
Pre-Building
Clone and install Netbee.
Build
NOX
Install all NOX dependencies
Build
OpenFlow dissector for Wireshark
Install Wireshark
Install scons
Set the Wireshark include directory
Building
Mininet
Download and Install
Starting the topology
Let's start a simple topology on mininet.
The command above will create a topology with a single switch connecting two hosts.
Using dpctl
Dpctl is a good utility to change and show the network state in a fast manner, avoiding changes to your controller when you want only punctual actions.
Let's see some examples and how to make the hosts of the topology created in the last step ping each other.
Further documentation and use cases are available in the links below:
Examples
Show all flows present in table 0.
Install a flow in the table 0, to match an IPv6 src address and output to port 2.
Install a flow in the table 0, with default parameters, matching on in_port and eth_type and a set_field action to rewrite the ip src.
Create a group.
Install flow with an action to send to the group created.
Create a meter with a 10MB rate limiting
Create a flow that points to a meter instruction
Ping between the topology hosts
Just add two rules to direct the traffic from the port 1 to port 2 and from port 2 to port 1.
Scriptflow 1.3 Free
Now try to execute ping the between the hosts on mininet.
Scriptflow 1.3 1Dissecting OpenFlow messages
Start Wireshark
To filter OpenFlow 1.3 messages type in the filter box near the top Photo sense 2.1.2 key.
Scriptflow 1.3 Mods
For example, to filter messages by the header present in all OpenFlow messages
Filter flow_mod messages
Creating a basic NOX application
It is strongly recommended to use a controller under constant development, such as Ryu or ONOS. I will keep this section just for past reference
Now it's time to learn about the modifications on the NOX C++ API needed to reflect OpenFlow 1.3 changes, showing the essential code that an application expects to run. For a more detailed description of NOX, as wewill focus on the API changes, please look at NOX Classic Wiki.
Typical application body
Every application developed in NOX should have a class which will have the name of your app. Mr. shifty 1.0 pro. That class will be where OpenFlow message handlers should be implemented plus a configure and an install methods. The configure method is useful to pass config arguments to the application, while the install method is used to register the message handlers.
Also, every class must inherit from Component and include the macro REGISTER_COMPONENT.
Registering for OpenFlow messages
The method install, as said, is used to install OpenFlow message handlers and it's slightly different from the NOX Classic. The example below illustrates how to register for a Packet_in event, which will be raised for every packet that goes to controller.
The message handler should be implemented on the class and always return a Disposition, which can be CONTINUE, to proceed the event to the next listener, or STOP, ending the event processing.
Creating and sending a Flow message
The NOX API relies on the oflib, used to convert messages between an OpenFlow format, which is how the message bytes will travel over the network and a Host format, to ease message manipulation. While it's possible to directly use the oflib structs to create and send messages, the TLV based match approach of OpenFlow 1.3 makes the creation of messages including these fields a bit more trickier. So To ease the creation of messages including match fields we provide an extension to the NOX API.
Let's see it by an example.
In the example above a flow_mod message is created with an in_port field to match every packet that comes by the port 2 and an action to send all matched packets to port 1.
Sending OpenFlow messages with NOX
To send the flow_mod message created above you should use the method send_openflow_msg. Any other OpenFlow message should be send using that.
App examples
For examples of NOX applications using our modified API, please take a look on the Hub and Switch in the nox13oflib repository.
Useful pages
You can find more information about Dpctl and NOX usage on the following pages:
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