System Administration Guide: IP Services

Defining Filters

You create filters to identify packet flows as members of a particular class. Each filter contains selectors, which define the criteria for evaluating a packet flow. The IPQoS-enabled system then uses the criteria in the selectors to extract packets from a traffic flow. The IPQoS system then associates the packets with a class. For an introduction to filters, see IPQoS Filters.

The following table lists the most commonly used selectors. The first five selectors represent the IPQoS 5-tuple, which the IPQoS system uses to identify packets as members of a flow. For a complete list of selectors, see Table 37–1.

Table 33–2 Common IPQoS Selectors




Source address. 


Destination address. 


Source port number. You can use a well-known port number, as defined in /etc/services, or a user-defined port number.


Destination port number. 


IP protocol number or protocol name that is assigned to the traffic flow type in /etc/protocols.


Addressing style to use. Use either IPv4 or IPv6. IPv4 is the default. 


Contents of the DS field, that is, the DSCP. Use this selector for extracting incoming packets that are already marked with a particular DSCP. 


Priority level that is assigned to the class. For more information, see How to Define the Classes for Your QoS Policy.


Either the UNIX user ID or user name that is used when the upper-level application is executed. 


Project ID that is used when the upper-level application is executed. 


Direction of traffic flow. Value is either LOCAL_IN, LOCAL_OUT, FWD_IN, or FWD_OUT.

Note –

Be judicious in your choice of selectors. Use only as many selectors as you need to extract packets for a class. The more selectors that you define, the greater the impact on IPQoS performance.