Quality of Service, or QoS, is used when implementing VoIP phones because voice traffic is sensitive to delay, jitter, and packet loss. QoS allows network administrators to classify and prioritize traffic so that real-time voice packets receive preferential treatment over less time-sensitive traffic such as file downloads, backups, or general web browsing. This helps maintain call quality, reduce dropped audio, and improve the user experience during periods of network congestion.
The CompTIA Network+ N10-009 objectives include traffic management, network performance, and services that require prioritization. VoIP is one of the most common examples of a service that benefits from QoS because voice communication must be delivered consistently and in sequence.
A VPN provides secure encrypted connectivity but does not inherently prioritize voice traffic. A CDN distributes content closer to users, typically for web or media delivery, and is not specifically used to implement VoIP phones. TTL, or Time to Live, is a packet field that helps prevent packets from circulating indefinitely in a network. Therefore, QoS is the correct answer for VoIP implementation.
