VoIP performance on differentiated services enabled network

We study the performance of voice over Internet protocol (VoIP) traffic aggregates over differentiated services (Diffserv) enabled network using expedited forwarding (EF) per hop behavior (PHB). We compare the delay and jitter performance of the VoIP traffic generated by different standard voice codec algorithms, both under Diffserv with EF PHB and with best-effort service. Both homogenous and heterogenous voice traffic aggregates are considered. Our results show that the use of EF yields very good performance improvement for voice traffic compared to best-effort. The improvement is greatest for high coding rate algorithms like G.711 than lower coding rate algorithms like G.723.1. For heterogenous traffic aggregates, the traffic from higher bit rate codecs obtains a better performance compared to lower bit rate codecs.