Which of the following best describes the role of the TPID field in the 802.1Q frame?

The TPID (Tag Protocol Identifier) field in an 802.1Q frame serves a crucial function by indicating the presence of VLAN (Virtual Local Area Network) tags in Ethernet frames. Specifically, the TPID field is set to a value of 0x8100, which is designated for VLAN tagging. This allows network devices to recognize that the frame contains information related to VLANs.

When a frame is transmitted over a network, the devices involved need to identify whether the frame is tagged with VLAN information. The TPID field achieves this by carrying the specific value that denotes VLAN tagging. This is essential for proper processing of frames in a switched network environment, where VLANs are used to segment traffic for improved security and performance. Identifying the presence of VLAN tags allows switches and routers to correctly manage traffic, ensuring that it reaches its appropriate destination according to the VLAN segmentation.

In summary, the TPID field plays a significant role in VLAN identification, facilitating the correct handling of tagged frames within an Ethernet network.