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Group table
The ability for a flow entry to point to a group enables OpenFlow to represent additional methods of
forwarding. A group table contains group entries.
Figure 4 Group entry components
A group entry contains the following fields:
• Group Identifier—A 32 bit unsigned integer uniquely identifying the group.
• Group Type—Type of the group: All—Execute all buckets in the group. This group is used for
multicast or broadcast forwarding.
• Counters—Updated when packets are processed by a group.
• Action Buckets—An ordered list of action buckets, where each action bucket contains a set of
actions to execute and associated parameters.
Meter table
Meters enable OpenFlow to implement various simple QoS operations, such as rate-limiting. A group
table contains meter entries.
Figure 5 Meter entry components
A meter entry contains the following fields:
• Meter Identifier—A 32 bit unsigned integer uniquely identifying the meter.
• Meter Bands—Each meter can have one or more meter bands. Each band specifies the rate at
which the band applies and the way packets should be processed. If the current rate of packets
exceeds the rate of multiple bands, the band with the highest configured rate is used.
• Counters—Updated when packets are processed by a meter.
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 to configure and manage the
switch, receive events from the switch, and send packets out the switch. The OpenFlow channel is
usually encrypted by using TLS. Also, an OpenFlow channel can be run directly over TCP.
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