Basic Components of OpenFlow Network

OpenFlow consists of OpenFlow switch, Flow Visor, and Controller. The OpenFlow switch performs data layer forwarding. The FlowVisor virtualizes the network and the Controller centrally controls the network to implement the functions of the control layer. The structure of the OpenFlow network is as follows:

 

OpenFlow Switch

The OpenFlow switch is the core component of the entire OpenFlow network and mainly manages data layer forwarding. After the OpenFlow switch receives the data packet, it first searches for the target forwarding port on the local stream table. If there is no match, it forwards the data packet to the Controller, which is determined by the control layer.

Composition of OpenFlow Switches

The OpenFlow switch consists of three parts: flow table, secure channel, and OpenFlow protocol.

The security channel is the interface connecting the OpenFlow switch to the Controller. The controller uses this interface to control and manage vswitches. At the same time, the Controller receives events from vswitches and sends packets to vswitches. Vswitches and controllers communicate through secure channels, and all information must be executed in the format specified by the OpenFlow protocol.

The OpenFlow protocol is used to describe the information used for interaction between the Controller and the switch, as well as the interface standards of the controller and the switch. The core part of the protocol is a collection of OpenFlow protocol information structures.

OpenFlow supports three types of information: Controller-to-Switch, Asynchronous, and Ric. Each type has multiple subtypes. The Controller-to-Switch information is initiated by the Controller and is directly used to detect the status of the Switch. Asynchronous information is initiated by the vswitch and is usually used to update the network events of the controller and change the status of the vswitch. The specified Ric information can be initiated by the Controller or vswitch without any request.

OpenFlow switch Classification

Based on the degree of support for OpenFlow, OpenFlow switches can be divided into two categories: dedicated OpenFlow switches and switches that support OpenFlow.

The dedicated OpenFlow switch is designed to support OpenFlow. It does not support normal processes on existing commercial switches. All data passing through the switch is forwarded in OpenFlow mode. The dedicated OpenFlow switch no longer has control logic. Therefore, the dedicated OpenFlow switch is a simple path component used to forward data packets between ports.

A vswitch that supports OpenFlow is a vswitch that adds a flow table, a secure channel, and an OpenFlow protocol based on a commercial vswitch to obtain the OpenFlow features. It has both common forwarding modules of commercial switches and the forwarding logic of OpenFlow. Therefore, switches supporting OpenFlow can process received packets in two different ways.

According to the degree of development of OpenFlow switches, OpenFlow switches can also be divided into two types: "Type0" switch and "Type1" switch.

The "Type0" Switch only supports the ten-element group and the following four operations: Forward the data packet of the stream to a given port or port); compress and forward the data packet of the stream to the Controller; the packet of the stream is discarded, and the packet of the stream is forwarded through the normal process of the switch.

Obviously, the functions of the "Type0" Switch cannot meet the requirements of complex experiments. Therefore, we will define the "Type1" switch to support more functions and support complex network experiments. The "Type1" switch will have a new feature set.

FlowVisor supporting network Virtualization

Similar to computer virtualization, FlowVisor is a virtual network layer between hardware components and software. FlowVisor allows multiple controls to simultaneously control an OpenFlow switch, but each controller can only control a virtual network (slice) that passes through the OpenFlow switch ). Therefore, the test platform established by FlowVisor allows multiple networks to be tested simultaneously on different virtual networks without affecting the forwarding speed of commercial streams. FlowVisor is compatible with general commercial switches, and does not require programmable hardware such as FPGA and network processors.

Controller

OpenFlow separates the data layer from the control layer. The OpenFlow switch forwards data layer, while the Controller implements the control layer function. The Controller controls the flow table in the OpenFlow switch through the standard interface of the OpenFlow Protocol to implement centralized control over the entire network. All the functions of Controller must be implemented by running NOX, so NOX is like the operating system of OpenFlow network. In addition, you can run applications such as Plug-n-serve, OpenRoads, and OpenPipes on NOX.

Plug-n-Serve controls the load on the network and the server by specifying the data transmission path, so as to balance the load and reduce the response time. OpenRoads is a framework that supports OpenFlow Wireless Network Mobility research. OpenPipes can move each sub-module in the network system to test each sub-module and decide how to divide the design unit.