802.1p is an IEEE (Institute of Electronic and Electrical Engineers) standard that assigns traffic priorities while executing dynamic multicast filtering for other network mechanisms. 802.1p offers higher reliability and quality by prioritizing specification support, thus achieving higher Quality of Service (QoS).

QoS is a system that endows better management of any data that passes through a network. There are two main classes of QoS – soft QoS and hard QoS. Soft QoS mainly involves data prioritization, while hard QoS deals with set capacities specific to certain types of service. QoS helps assure that integral data packets get to their destinations in the shortest span of time.

The IEEE 802.1p standard assigns priority to packets crossing a network. The standard operates with the Media Access Control (MAC) header in the data link level. The MAC header is a portion monitored by a network’s switches and hubs. These devices also distinguish packets based on their priorities within the network.

802.1p designates prioritization by setting a value within the MAC header. This value’s priority levels range from 0–7 (covering a sum of 8 levels), with level 0 denoting the lowest priority and level 7 being the highest. This allows packets to group and create various traffic classes. When network overcrowding happens, packets with low priority will be held temporarily while high-priority packets will be managed first.

802.1p cannot work with older switches. Coexistence of the 802.1p with non-802.1p standards may lead to network instability. Older standards are bound to misread the header used by 802.1p protocol. For a network to operate properly, it is important that the device drivers, Ethernet cards, and the switches are compatible with 802.1p.