Flow Table

The flowacct module maintains a flow table that records all packet flows that are seen by a flowacct instance. A flow is identified by the following parameters, which include the flowacct 8–tuple:

• Source address

• Destination address

• Source port

• Destination port

• DSCP

• User ID

• Project ID

• Protocol Number

If all the parameters of the 8–tuple for a flow remain the same, the flow table contains only one entry. The max_limit parameter determines the number of entries that a flow table can contain.

The flow table is scanned at the interval that is specified in the IPQoS configuration file for the timer parameter. The default is 15 seconds. A flow “times out” when its packets are not seen by the IPQoS system for at least the timeout interval in the IPQoS configuration file. The default time out interval is 60 seconds. Entries that have timed out are then written to the accounting file that is created with the acctadm command.