IEEE 802.11 wireless local area network (WLAN) has become popular and has been providing excellent solution for wireless networking. With the popularity of WLAN and Voice over the Internet (VoIP) protocol, it is very essential to measure the performance of the VoIP over WLAN. The main goal of this paper is to compare the performance of the Voice over IP protocol in both LAN (802.3) and WLAN (802.11). This paper examines how this communication protocol performs in two different network setups and analyzes the results obtained using OPNET modeler. It also examines the optimization of 802.11e for Quality of Service (QoS) using the priorities to provide real-time service for voice over the Internet protocol.