Comparison of IPv4 and IPv6 QoS implementations using Differentiated Services

Real-time applications such as VoIP place stringent demands on network QoS. However, IP is a best-effort service and is often unable to offer the levels of QoS required for real-time applications. One mechanism that has been commonly used to address this issue in IP networks is Differentiated Services (DiffServ). This paper describes the use of DiffServ in IPv4 and IPv6 networks, and implementation and evaluation of VoIP QoS within OPNET IT Guru. The simulation results demonstrated that DiffServ improved the performance of VoIP traffic in both IPv4 and IPv6, allowing previously congested networks to deliver VoIP with an acceptable QoS. However the simulations also showed that the performance of DiffServ in IPv6 is slightly worse than in IPv4. A number of possible reasons for this outcome are proposed along with recommendations for further research.