IEEE 802.1p

A three-bit CoS priority field within the greater 802.1Q format running at layer 2.

802.1p can be used independently or in conjunction with Differentiated-Service-Framework to classify and prioritize traffic passing over a switch or WAP. The three bit priority field in the 802.1Q VLAN field allows for the values 0-7 to be set. Usually, vendors map the 3 bits to equivalent values in the DiffServ Code Point (DSCP) priority value set.

• 0-1 - Best Effort (we'll get to you when we can)
• 2-3 - Assured Forwarding (elevated priority)
• 4-5 - Expedited Forwarding (high priority)
• 6-7 - Network Updates (e.g. routing table updates, highest priority)