CoS 802.1p-Based Traffic Groups
CoS 802.1p-based traffic groups forward traffic to QoS features based on the three 802.1p priority bits in an Ethernet frame. The 802.1p priority bits are located between the 802.1Q type field and the 802.1Q VLAN ID as shown in 802.1p Priority Bits.
Typically CoS will be used in conjunction with policy, however it may also work independently. In a policy-enabled system, policy may use any CoS index setting (0-255) to configure ACLs to assign a qosprofile, meter, dot1p replacement and TOS-rewrite value. By default, 802.1p priorities 0-7 are mapped to CoS indices 0-7.
The three 802.1p priority bits define up to eight traffic groups that are predefined in the ExtremeXOS software.
On SummitStack and ExtremeSwitching series switches, the traffic groups direct traffic to egress QoS profiles for egress rate shaping (see the following table).
You do not need to define 802.1p-based traffic groups. You can enable or disable the use of these traffic groups by enabling or disabling the 802.1p examination feature. You can also configure which 802.1p values map to which QoS profiles.
A related feature is the 802.1p replacement feature, which allows you to configure the software to replace the 802.1p bits in an ingress frame with a different value in the egress frame. For more information on 802.1p replacement, see Configuring 802.1p or DSCP Replacement.