Sync & Sense: VoIP Measurement Methodology for Assessing One-Way Delay Without Clock Synchronization
Boonchai Ngamwongwattana, Richard A. Thompson · IEEE Transactions on Instrumentation and Measurement · 2010
It is well known that measuring the one-way delay of voice-over-IP (VoIP) packets is a daunting task. The challenge lies in the fact that the Internet implicitly enforces the end-to-end principle. This means that the endpoints are expected to operate independently. Without a synchronized timing, it is difficult for an endpoint to measure the one-way delay. This paper presents the refined version of the novel VoIP measurement methodology called Sync & Sense of Periodic Stream that can overcome such a challenge. Sync & Sense is unique in that it can virtually synchronize the transmission and reception timing of the VoIP session without requiring a synchronized clock. Our performance study shows that Sync & Sense can accurately measure the one-way network delay of the VoIP packets (without propagation delay). While time skew is very common in any system involving a clock, we also discuss this issue and how Sync & Sense can deal with the time skew without requiring a synchronized clock.