This paper investigates the performance of VoIP over a BGP/MPLS VPN network from two different aspects. The first aspect investigates the impact on VoIP performance of the VPN tunneling process. This is based on a comparison of VoIP performance over a BGP/MPLS VPN network with its
performance over an MPLS network, with particular regard to different QoS parameters, principally delay, jitter and throughput. The second aspect is a study of the most common VoIP codecs, namely, G.711, G.723.1 and G.729A over the BGP/MPLS VPN network. This is based on investigating
different implementations of such codecs with respect to the packetization interval time in order to identify the optimal codec that efficiently balances between acceptable end-to-end delay and high bandwidth efficiency.The OPNET Modeler was used to create a VoIP-BGP/MPLS VPN simulation model for carrying out different scenarios. The results show that the BGP/MPLS VPN network has a positive impact on VoIP performance in comparison with its performance over an MPLS network. It also concludes that, following different implementations of the VoIP codecs, G.729A is the best codec for the VoIP-BGP/MPLS VPN network as it efficiently balances between bandwidth efficiencyand low end-to-end delay.