Alcatel-Lucent 6850-48 Network Guide

QoS Ports and Queues

Configuring QoS

page 40-28

OmniSwitch AOS Release 6 Network Configuration Guide

By default switch ports are not trusted; that is, they do not recognize 802.1p or ToS/DSCP settings in 
packets of incoming traffic. When a port is not trusted, the switch sets the 802.1p or ToS/DSCP bits in 
incoming packets to the default 802.1p or DSCP values configured for that port. 

 commands are used to specify the default 802.1p 

and ToS/DSCP values. If no default is specified, then these values are set to zero.

Note that on the OmniSwitch 6800, the 802.1p bit for tagged packets received on untrusted ports is set 
with the default 802.1p value. If the packet is untagged, however, then the DSCP bit is set with the default 
DSCP value.

Fixed ports that are configured for 802.1Q are always trusted, regardless of QoS settings. They cannot be 
configured as untrusted. For more information about configuring 802.1Q for fixed ports, see 

Mobile ports are also always trusted; however, mobile ports may or may not accept Q-tagged traffic.

Note about mobile ports. Mobile ports cannot be Q-tagged like fixed ports; however, a mobile port will 
join a tagged VLAN if tagged traffic for that VLAN comes in on the mobile port and the 

command is enabled for that VLAN. For more information about enabling this command, see 

Ports must be both trusted and configured for 802.1Q traffic in order to accept 802.1p traffic. 

The following applies to ports that are trusted (for 802.1p traffic, the ports must also be able to accept 
802.1Q packets):

• The 802.1p or ToS/DSCP value is preserved.

• If the incoming 802.1p or ToS/DSCP flow does not match a policy, the switch places the flow into a 

default queue and prioritizes the flow based on the 802.1p or ToS/DSCP value in the flow. 

• If the incoming 802.1p or ToS/DSCP flow matches a policy, the switch queues the flow based on the 

policy action.

The switch may be set globally so that all ports are trusted. Individual ports may be configured to override 
the global setting.

By default, all ports (except 802.1Q-tagged ports and mobile ports) are untrusted. The trust setting may be 
configured globally on the switch, or on a per-port basis.

To configure the global setting on the switch, use the 

 command. For example:

-> qos trust ports

To configure individual ports as trusted, use the 

 command with the desired slot/port 

number. For example:

-> qos port 3/2 trusted