OpenFlow flow table

An OpenFlow switch matches packets with one or more flow tables. A flow table contains flow entries, and packets are matched based on the matching precedence of flow entries.

OpenFlow flow tables include the following types:

Flow entry

Figure 2: Flow entry components

A flow entry contains the following fields:

OpenFlow pipeline

The OpenFlow pipeline processing defines how packets interact with flow tables contained by a switch.

The flow tables of an OpenFlow switch are sequentially numbered, starting at 0. The packet is first matched with flow entries of the first flow table, which is flow table 0. A flow entry can only direct a packet to a flow table number that is greater than its own flow table number.

When a packet matches a flow entry, the OpenFlow switch updates the action set for the packet and passes the packet to the next flow table. In the last flow table, the OpenFlow switch executes all actions to modify packet contents and specify the output port for packet forwarding. If the instruction set of a flow table contains an action list, the OpenFlow switch immediately executes the actions for a copy of the packet in this table.

Figure 3: OpenFlow forwarding workflow

Table-miss flow entry

Every flow table must support a table-miss flow entry to process table misses. The table-miss flow entry specifies how to process packets that were not matched by other flow entries in the flow table.

The table-miss flow entry wildcards all match fields (all fields omitted) and has the lowest priority 0.

The table-miss flow entry behaves in most ways like any other flow entry.