Open Flow Overview

Open Flow is a Standard based Layer 2 Communication protocol used between Controller and Switch in SDN. It allows to access to the Forwarding Plane of the network devices. OpenFlow was standardised by a non-profit consortium, Open Networking Foundation (ONF) that has many network vendors as a member. This protocol had firstly developed for testing the new protocols in campus networks. But later, it has evolved to used in SDN.

Generally, Open Flow is mixed with SDN. But this is not true, SDN is not Open Flow. Open Flow is a subset of SDN. Let’s see the difference of these two terms.

SDN (Software-Defined Networking) is the name of the general new network concept that seperate forwarding plane and control plane of the network. It is the top term, that includes Open Flow, Controllers, Network Devices etc.

Open Flow is the protocol used in SDN, that is used to communicate forwarding plane and control plane of the network. In other words, the communication between Controller and the Network Devices are done with Open Flow. It allows operations, manuplations on Network Devices over Open Flow Interface.

Open Flow has some common roles. A nice summary of these roles are given below:

Open Flow allows separation of control and data planes in the network.
It provides centralization of the control.
Open Flow uses Flow based control mechanism.
Takes advantage routing tables in Ethernet switches and routers.

Open Flow Versions

The fisrt version of Open Flow was Open Flow 1.0. After the beginning through today, six versions has developed. These versions are :

1.0
1.1
1.2
1.3
1.4
1.5
1.6

The next version will be Open Flow 2.0.

What are the developments with these Open Flow versions? Let’s check these as a summary.

Open Flow 1.0 was the first Open Flow version at 2009. Open Flow 1.0 was supporting single Flow Table and 12 fixed match filed in the Flow rules.

With Open Flow 1.1, at 2011, Multi-table support has come with also a group table. Beside these, Open Flow 1.1 has brought VLAN and MPLS support.

After Open Flow 1.1, Open Flow 1.2 was developed at the late 2011. Open Flow 1.2 was the first ONF release. It was more flexible than the previous versions. Beside this, it support IPv6 and Role Change.

Open Flow 1.3 was a long release, that has sub releases (Open Flow 1.3.1, Open Flow 1.3.2, Open Flow 1.3.3). It was developed at 2012. Event Filters, PBB and Meters was the new features of Open Flow 1.3).

At 2013, Open Flow 1.4 has brought many features after Open Flow 1.3. Synronized Tables, Bundles, Optical Ports, Flow Monitoring are some of them.

Lastly, at 2015, Open Flow 1.5 has come. With Open Flow 1.5 Egress Table and Packet Type avare pipelines are developed.

After now, the new version should be Open Flow 2.0.