I am confused between the following terms: OpenFlow, Open vSwitch, and Mininet. I want to understand the relationships between them. Kindly, can someone provide when and how to use each one of them?
Thank you.
Let me explain OpenFlow first. In traditional legacy network devices, the control decisions unit and the forwarding unit are tightly coupled (like switches, routers, etc., where both the control decisions like say, optimal route calculation and the forwarding occur in the same device). The hardware of these devices is made specifically for a particular task. They are not flexible enough to allow researchers to test new algorithms that they might come up with to solve any of the networking issues (say they have a better congestion-control algorithm for TCP!). This requires researchers to create their own custom hardware and have a whole new setup for each experiment.
It would be a lot better if commercial switch providers allowed more flexibility, thus allowing researchers to test their new idea on the same network without new hardware.
As per the white paper on OpenFlow, an OpenFlow switch allows this flexibility and OpenFlow is the protocol used to manage the switch (i.e., add/remove/modify flow entries, capture flow statistics, etc.,). The user program that uses OpenFlow to communicate with the OpenFlow switch is called the controller. There are various frameworks available for writing controller applications. Examples are Ryu are OpenDaylight.
SDN is based on this idea of de-coupling the control and forwarding unit (also called the data plane). Not only is this useful for researchers, but also for data centers, as it reduces the cost of changing hardware each time a change is required.
OpenVSwitch - The 'V' stand for Virtual. This is a "virtual" OpenFlow switch. Apart from OpenFlow, it also supports other switch management protocols.
Many people ask if an OpenFlow switch operates at layer 2 or layer 3. Note that there is no such concept here. In an OpenFlow switch, forwarding decisions can be taken based on MAC, IP, in-port, VLAN_ID, etc., So Please don't try to fit this into the OSI model.
Mininet is a network emulator. The user can create any kind of topology with multiple hosts and switches. The type of the switch could also be chosen.