Quality of Service (QoS) for Voice/IP has been researched extensively for INTERNET. While many products are available, Voice/IP application suffers from loss of voice either one side or on both sides under significant congestion in the network. These networks only provide some improvements to QoS offering within INTERNET, but fail to consider enterprise and access network variable delays. In this paper, we propose a novel tri-mode control of Coefficient of Variance to control and maintain high end-to-end Quality of Service (QoS) for Voice/IP (VOIP) application for each source-destination pair regardless of the network behavior. Coefficient of Variance (CV) is the ratio of standard deviation of the delay and the expected delay in each ensemble of VOIP packets. This technique allows provisioning of a real time distributed control of VOIP QoS dynamically. In this paper, the analysis of CV control in each mode is shown. It demonstrates the controlled CV which assures high end-to-end QoS for a source-destination pair. The overall VOIP system has been implemented using a real time network emulator to vary the traffic conditions and verify the proposed control to assure high end-to-end QoS for each source-destination pair.