The computers and IP phones at an office experience degraded performance during the day.

Degraded performance that occurs only during business hours strongly suggests network congestion caused by simultaneous data and voice traffic. According to CompTIA Core 1 (220-1201) networking objectives, combining voice (VoIP) and data traffic on the same network without proper segmentation can lead to latency, jitter, and packet loss, especially during peak usage periods.

Implementing VLANs (Virtual Local Area Networks) allows administrators to logically separate voice and data traffic, enabling better traffic management and prioritization. VLANs also support Quality of Service (QoS) policies that ensure time-sensitive voice traffic is prioritized over standard data traffic, improving call quality and overall performance.

Replacing switches with higher-capacity models is costly and unnecessary if proper traffic segmentation has not yet been implemented. Adding RAM to PCs or VoIP lines does not address network-level congestion. Firmware updates may improve stability but will not resolve sustained performance degradation caused by traffic contention.

CompTIA highlights VLAN implementation as a best practice for environments that use IP phones, especially when performance issues occur during high utilization periods.