8021Q2014

8021Q2014, formally IEEE Std 802.1Q-2014, is the IEEE standard revision for virtual local area networks (VLANs) on Ethernet networks. It defines the frame tagging mechanism that enables a single network to carry multiple logical networks, improving traffic management, security, and scalability. The 2014 revision updates the tagging specification to reflect modern interoperability and deployment practices while remaining compatible with earlier implementations.

Frame tagging and format: A VLAN tag is inserted into an Ethernet frame after the source MAC address and before the EtherType/length field. The tag control information (TCI) is 16 bits and consists of a 3-bit Priority Code Point (PCP) used for traffic prioritization, a 1-bit Drop Eligible Indicator (DEI; previously known as Canonical Format Indicator), and a 12-bit VLAN Identifier (VID). The Ethertype/length field value for VLAN-tagged frames is 0x8100, followed by the TCI. VLAN IDs in practical use range from 1 to 4094; 0 is reserved for priority tagging and 4095 is reserved for future use.

Operation and deployment: The standard specifies how switches and bridges should process tagged frames on access and trunk ports, enabling segregation of traffic into distinct VLANs. It supports common VLAN models such as port-based VLANs and VLAN-aware bridging and is compatible with related IEEE 802.1 specifications, including VLAN stacking concepts described in other parts of the 802.1 family.

Implementation and usage: 802.1Q-2014 is widely implemented by network equipment vendors and underpins VLAN-based segmentation in enterprise networks, data centers, and campus networks. It remains a foundational element for quality of service, security boundaries, and scalable network architecture.

See also: IEEE 802.1Q, VLAN, VLAN tagging. References: IEEE Std 802.1Q-2014.