With the tremendous growth in data traffic due to the increase in the number of devices connected to networks, and more and more applications moving into the cloud, service providers are moving towards virtualizing their infrastructure. With storage and computing virtualization, there is a clear necessity to provide virtualization in networks and a standardized way of programming network devices. With large data centers, there is also a clear necessity to change the traditional control plane and data plane paradigm to move towards flow-based switching, which is more generic and can be adapted for different avenues. Today's networks have evolved into complex proprietary systems, with little chance of offering any possibility to carry out experiments on new ideas or protocols. The Open Network Foundation (ONF) has come up with a specification to meet these requirements and has called it OpenFlow. The latest version of this specification is OpenFlow 1.4.
OpenFlow paves the way for the traditional network to be a programmable network, with standard interfaces between the controller (traditionally called a control plane) and the actual packet forwarding entity (traditionally called a data plane). OpenFlow was started as a means to try experimental ideas/protocols on large-scale networks by providing a standard, flow-based table called an OpenFlow table and separating the control plane from the data plane. This offers the possibility to program the forwarding decisions of those network devices supporting the OpenFlow specification in a flexible manner. There are two main components of the OpenFlow specification, the switch and the controller. This book describes in brief both the OpenFlow switch and controller, their operations, and so on.
An OpenFlow switch consists of one or more flow tables and group tables that perform packet lookups and forwarding. Each flow table in the switch contains a set of flow entries. Each flow entry consists of match fields, counters, and a set of instructions to apply to matching packets. The switch communicates with the controller and the controller manages the switch via the OpenFlow channel, using the OpenFlow protocol.
The OpenFlow controller is a software application that manages the switch using the OpenFlow protocol. The controller can add, update, and delete flow entries in flow tables, both reactively (in response to packets) and proactively.
This Cookbook provides an easy, more user-friendly and step-by-step approach to develop and understand OpenFlow switch and controller. Organized into two parts, part 1 explains OpenFlow from the switch point of view and part 2 explains it from the controller’s point of view. You will see a 1:1 mapping between part I and part 2 chapters and recipes to provide a clear demarcation of the operations and responsibilities of the switch and controller.