System Administration Guide: IP Services

Using the dlcosmk Marker With VLAN Devices

The dlcosmk marker module marks a forwarding behavior in the MAC header of a datagram. You can use dlcosmk only on an IPQoS system with a VLAN interface.

dlcosmk adds four bytes, which are known as the VLAN tag, to the MAC header. The VLAN tag includes a 3-bit user-priority value, which is defined by the IEEE 801.D standard. Diffserv-aware switches that understand VLAN can read the user-priority field in a datagram. The 801.D user priority values implement the class-of-service (CoS) marks, which are well known and understood by commercial switches.

You can use the user-priority values in the dlcosmk marker action by defining the class of service marks that are listed in the next table.

Table 37–3 801.D User-Priority Values

Class of Service 


Best effort 



Excellent effort 

Controlled load 

Video less than 100ms latency 

Video less than 10ms latency 

Network control 

For more information on dlcosmk, refer to the dlcosmk(7ipp) man page.

IPQoS Configuration for Systems With VLAN Devices

This section introduces a simple network scenario that shows how to implement IPQoS on systems with VLAN devices. The scenario includes two IPQoS systems, machine1 and machine2, that are connected by a switch. The VLAN device on machine1 has the IP address The VLAN device on machine2 has the IP address

The following IPQoS configuration file for machine1 shows a simple solution for marking traffic through the switch to machine2.

Example 37–2 IPQoS Configuration File for a System With a VLAN Device

fmt_version 1.0
action {
        module ipgpc
	      name ipgpc.classify

        filter {
                name myfilter2
                class myclass

        class {
                name myclass
                next_action mark4

action {
        name mark4
        module dlcosmk
        params {
                cos 4
                next_action continue
		global_stats true

In this configuration, all traffic from machine1 that is destined for the VLAN device on machine2 is passed to the dlcosmk marker. The mark4 marker action instructs dlcosmk to add a VLAN mark to datagrams of class myclass with a CoS of 4. The user-priority value of 4 indicates that the switch between the two machines should give controlled load forwarding to myclass traffic flows from machine1.