QoS Measurement of VoIP End-points

VoIP (Voice over IP) is a service that requires synergy between the underlying network for transport and the endpoints responsible for voice processing. We evaluate the end-to-end quality and performance of several VoIP end-points. In particular, we focus on the following aspects: mouth-to-ear (M2E) delay, clock skew and behavior under packet loss. Our measurement results show that M2E delay depends mostly on the receiving end-point, and when hardware IP phones act as receivers, they achieve low average M2E delay (45-90ms) in a LAN environment. For software VoIP clients as receivers, their average M2E delays range from 65ms to over 400ms. We find that all tested hardware IP phones support some form of packet concealment and it works well for up to two consecutive losses at 20 ms packet intervals. Keyword IP Telephony, voice over IP, quality of service, end-to-end, delay, jitter