A Quality of Service (QoS) configuration on a Layer 3 capable switch allows the switch to prioritize VoIP traffic over other types of network traffic. This helps in maintaining the call quality and reliability expected of VoIP communications by reducing latency, jitter, and potential packet loss. A router is capable of QoS but typically operates at the network edge and may not prioritize internal traffic. Access points may implement QoS for wireless traffic, but prioritization across the entire network is better managed by switches. While a firewall can also manipulate traffic, its main role is security, not traffic prioritization within the LAN.