CCIE network engineers quickly master the working principle of advanced technology Openflow
OpenFlow can be used to control and manage the switching module by the controller.
The OpenFlow channel is established between the controller and the exchange module to realize information exchange. When the switch module establishes multiple connections with multiple controllers through OpenFlow, then the controller will inform the switch module of its role through the OpenFlow channel. Subsequently, the controller delivers the forwarding information database or flow table to the switching module through the OpenFlow channel. Data forwarding is accomplished by the exchange module performing protocol calculations based on the forwarding information database to generate ARP entries, or based on flow table information.
By establishing an OpenFlow channel, before implementing information exchange between the controller and the exchange module, you need to understand the process of establishing and maintaining the openflow channel. After that, the openflow channel needs to be maintained.
1. After configuring OpenFlow connection parameters on the controller and switch module, the controller and switch module will establish a TCP connection.
2. After the TCP connection is successfully established, the controller and the switching module will send HELLO messages to each other to negotiate the channel. The hello message will carry the OpenFlow protocol version number and other information.
3. After successful channel negotiation, the controller sends a FEATURES_REQUEST message to query the attribute information of the switching module. The switching module reports its attribute information to the controller through the FEATURES_REPLY message. At this point, the OpenFlow channel is successfully established.
4. After the channel is established successfully, the controller and the switching module send ECHO messages to detect the connection status of the peer device. Generally speaking, the end that initiates the test will periodically send an ECHO_REQUEST message, and the peer end will respond to the ECHO_REPLY message after receiving the message. If the transmission fails five times in a row or does not receive the ECHO_REPLY message, it is determined that the peer end is faulty, and the OpenFlow connection is disconnected. If other packets are received during the period, the timer is restarted.
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