How many bits in length is the TPID field of the 802.1Q tag?

The TPID (Tag Protocol Identifier) field of the 802.1Q tag is 16 bits in length. This field is crucial for identifying Ethernet frames that contain a VLAN tag, allowing devices to recognize and process VLAN information appropriately. The TPID value for a standard VLAN tag is set to 0x8100, which indicates that the frame includes an 802.1Q tag.

This length is significant as it distinguishes the tagged frame from normal Ethernet frames, ensuring that switches and other network devices can handle toggled data flows in a multi-VLAN environment. The other options do not align with the defined structure of the 802.1Q standard, making the 16-bit TPID the correct choice.