An administrator can use packet tags to configure which of the following?

VLANs use 802.1Q frame tags to segment Layer 2 traffic, but these tags define broadcast domain membership rather than traffic priority or QoS behavior.

NAT (Network Address Translation) translates IP addresses between private and public address spaces and does not use packet tagging to function.

PoE (Power over Ethernet) delivers electrical power over Ethernet cables to devices and is a physical-layer feature unrelated to packet tags or traffic classification.

QoS relies on packet tags - specifically DSCP (Differentiated Services Code Point) values in IP packet headers or 802.1p priority bits in Ethernet frame headers - to mark traffic with a priority level. Network devices read these tags to make forwarding decisions that favor high-priority traffic such as VoIP or video conferencing over lower-priority data. This tagging mechanism is the foundational configuration method for implementing QoS policies across a network.