<p>You'll need to read the specifications yourself, the official URL is:</p>

<p><a href="https://www.opennetworking.org/sdn-resources/technical-library" rel="nofollow">https://www.opennetworking.org/sdn-resources/technical-library</a></p>

<p>Each specification has the historical change logs for all previous versions listed in Appendix B.</p>

<p>Some advice: Start with Openflow 1.0, then read the 1.0.1 errata which clarifies things a bit. Then read the newer versions if you really need to. The newer versions > 1.0 add a <em>lot</em> of complexity which makes them hard to understand if you don't know Openflow 1.0 already.</p>

<p>Personal note: Most publicly available implementations still only support version 1.0, newer ones have recently started to support v.1.3. A lot of research is still being done with v.1.0, so it's not completely obsolete yet. Newer versions are mainly extensions of Openflow 1.0, possibly with some fixes for edge cases and the like.</p>

<p>Other resources: This document by the Open vSwitch maintainers has an overview of some things that changed over time (with tables comparing versions):</p>

<p><a href="http://openvswitch.org/support/dist-docs/DESIGN.md.txt" rel="nofollow">"Design Decisions in Openflow"</a></p>

<p>It may also help to read the Wiki pages and archived discussions leading up to the release of Openflow 1.0 on the previous website (not maintained anymore):</p>

<p><a href="http://archive.openflow.org/wk/index.php/OpenFlow_Releases" rel="nofollow">http://archive.openflow.org/wk/index.php/OpenFlow_Releases</a></p>

<p>Finally, you may want to take a look at a survey paper to get an overview over some of the projects being worked on, e.g. this one:</p>

<p><a href="http://arxiv.org/abs/1406.0440" rel="nofollow">"Software-Defined Networking: A Comprehensive Survey"</a></p>
difference b/w openflow protocol versions?
<p>I'm new to openflow protocol. I think, there are 5 version of openflow protocol available (1.1 to 1.5). Can somebody help me out in understanding or a provide a link which summarizes the difference b/w these versions?</p>

<p>Thanks</p>