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What Is OpenFlow?
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| bet | 2/3 | | Sana | 29.02.2024 | | Hajmi | 94.65 Kb. | | #164416 |
Bog'liq What Is OpenFlow 1. Anketa (talabalar), 3-mavzu, conference, 12 labaratoriya ishi, Маълумотлар тузилмаси ва алгоритмлар узб, Abduvositaka, Saralash algoritmlari, Akademik yozuv 2 Omonboyev Rashidbek 12, kontakt hodisalar, golosariy, Operatsion tizimlar uz, 1 - lesson (internet), 2-маруза мавзуси Симулятор, dars tahlili, 6666666666666666666666666666666666666How OpenFlow Works
The OpenFlow architecture consists of a controller, OpenFlow switch, and secure channel. The controller controls the network in a centralized manner to implement the functions of the control layer. The OpenFlow switch is responsible for forwarding at the data layer; it exchanges messages with the controller through a secure channel to receive forwarding entries and report its status.
OpenFlow architecture
OpenFlow Controller
An OpenFlow controller is the brain of the SDN architecture and is located at the control layer to instruct data forwarding through the OpenFlow protocol. Currently, mainstream OpenFlow controllers are classified into two types: open-source controllers and vendor-developed commercial controllers. The widely used open-source controllers include NOX, POX, and OpenDaylight. Huawei's iMaster NCE controllers are commercial ones.
OpenFlow Secure Channel
A secure channel is established between a controller and an OpenFlow switch. Through this channel, the controller controls and manages the switch, and receives feedback from the switch.
The messages exchanged over the OpenFlow secure channel must comply with the format specified by the OpenFlow protocol. The OpenFlow secure channel is usually encrypted using Transport Layer Security (TLS), but may be run directly over TCP in plain text in OpenFlow 1.1 and later versions. The following OpenFlow messages are transmitted over the channel:
Controller-to-Switch message: is sent by the controller to the OpenFlow switch to manage or obtain the OpenFlow switch status.
Asynchronous message: is sent by the OpenFlow switch to the controller to update network events or status changes to the controller.
Symmetric message: is sent without solicitation by either the OpenFlow switch or the controller. It is mainly used to set up a connection and detect whether the peer is online.
OpenFlow Switch
As a core component of the OpenFlow network, an OpenFlow switch is mainly responsible for forwarding at the data layer. It can be a physical or virtualized switch/router. OpenFlow switches are classified into the following types based on their support for OpenFlow:
Dedicated OpenFlow switch: is a standard OpenFlow device that supports only OpenFlow forwarding. The switch processes all traffic that passes through it in OpenFlow mode, and cannot perform Layer 2 or Layer 3 forwarding on the traffic.
OpenFlow-compatible switch: supports both OpenFlow forwarding and Layer 2/3 forwarding. It is a commercial switch that supports OpenFlow features such as flow tables and secure channels.
An OpenFlow switch forwards packets entering the switch based on the flow table, which contains a set of policy entries instructing the switch on how to process traffic. Flow entries are generated, maintained, and delivered by a controller.
Flow entry
Traditional network devices such as switches and routers forward data based on the locally saved Layer 2 MAC address forwarding table, Layer 3 IP address routing table, and transport-layer port numbers. OpenFlow switches forward data based on flow tables that contain network configuration information of all layers on the network, instead of 5-tuple information. The entries in a flow table are flexible combinations of certain keywords and actions.
Each flow entry in an OpenFlow flow table consists of match fields and a set of instructions applying to matching packets. When receiving a data packet, an OpenFlow switch parses and matches the packet header against match fields in the flow entries, and executes the corresponding instruction if a match is found.
The flow entry structure varies according to the OpenFlow versions, as shown in Figure 1-5.
Flow entries in different OpenFlow versions
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