H3C Technologies H3C S6800 Series Switches - Manual (Page 14)

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Figure 6 Band components
A meter band contains:
• Band Type—Packet processing methods. Packets that exceed the band rate are dropped.
• Rate—Defines the lowest rate at which the band can apply.
• Counters—Updated when packets are processed by a band.
• Type Specific Arguments—Some band types have optional arguments.
OpenFlow channel
The OpenFlow channel is the interface that connects each OpenFlow switch to a controller. The controller
uses the OpenFlow channel to exchange control messages with the switch to perform the following
operations:
• Configure and manage the switch.
• Receive events from the switch.
• Send packets out the switch.
The OpenFlow channel is usually encrypted by using TLS. Also, an OpenFlow channel can be run directly
over TCP.
The OpenFlow protocol supports the following message types: controller-to-switch, asynchronous, and
symmetric. Each message type has its own subtypes.
Controller-to-switch messages
Controller-to-switch messages are initiated by the controller and used to directly manage or inspect the
state of the switch. Controller-to-switch messages might or might not require a response from the switch.
The controller-to-switch messages include the following subtypes:
• Features—The controller requests the basic capabilities of a switch by sending a features request.
The switch must respond with a features reply that specifies the basic capabilities of the switch.
• Configuration—The controller sets and queries configuration parameters in the switch. The switch
only responds to a query from the controller.
• Modify-State—The controller sends Modify-State messages to manage state on the switches. Their
primary purpose is to add, delete, and modify flow or group entries in the OpenFlow tables and to
set switch port properties.
• Read-State—The controller sends Read-State messages to collect various information from the
switch, such as current configuration and statistics.
• Packet-out—These are used by the controller to send packets out of the specified port on the switch,
or to forward packets received through packet-in messages. Packet-out messages must contain a full
packet or a buffer ID representing a packet stored in the switch. The message must also contain a
list of actions to be applied in the order they are specified. An empty action list drops the packet.
• Barrier—Barrier messages are used to confirm the completion of the previous operations. The
controller send s Barrier request. The switch must send a Barrier reply when all the previous
operations are complete.
• Role-Request—Role-Request messages are used by the controller to set the role of its OpenFlow
channel, or query that role. It is typically used when the switch connects to multiple controllers.