Which protocol is relied upon for VLAN identification in trunking?

The 802.1Q Protocol is the standard used for VLAN tagging in Ethernet frames, which is essential for VLAN identification during trunking. This protocol adds a tag to Ethernet frames that indicates the VLAN to which the frame belongs. When a trunk link carries multiple VLANs, each frame must be identified so that devices can properly handle the data according to its VLAN membership. The 802.1Q tag includes a 4-byte header that specifies the VLAN ID, thus enabling switches to ignore or forward traffic based on VLAN configuration.

Understanding this tagging mechanism is crucial for managing traffic within networks that utilize VLANs, particularly in environments where multiple broadcast domains are needed but must be transmitted over a common physical infrastructure.