Which of the following supports IP telephony devices without requiring external power?

VPN (Virtual Private Network) creates an encrypted tunnel for secure remote network access - it is a security and connectivity technology with no power delivery capability.

PoE (Power over Ethernet), defined by IEEE 802.3af and 802.3at standards, allows network switches and injectors to deliver DC electrical power alongside data signals over standard Cat5 or higher Ethernet cabling. This eliminates the need for external power supplies or nearby electrical outlets for IP telephony devices and other network equipment like wireless access points. A PoE-enabled switch or midspan injector detects compatible devices and supplies the appropriate power level automatically.

QoS (Quality of Service) is a network traffic prioritization mechanism that ensures voice and video packets receive preferential treatment for consistent call quality - it does not supply power to devices.

WEP (Wired Equivalent Privacy) is a deprecated wireless security encryption protocol - it is a security standard and has no relationship to device power delivery.