Voice over IP performance monitoring

TLDR

The study proposes a VoIP monitoring method that reduces the ITU‑T E‑Model to transport‑level, measurable quantities. The approach identifies key transport‑level metrics—delay, packet loss, and decoder de‑jitter buffer loss—and evaluates monitor placement within gateways or the transport path. The study finds that delay, network packet loss, and decoder de‑jitter buffer loss are the critical metrics, that in‑path monitoring requires a reference de‑jitter buffer to estimate voice quality, and that further research on codec performance under realistic loss patterns is needed.

Abstract

We describe a method for monitoring Voice over IP (VoIP) applications based upon a reduction of the ITU-T's E-Model to transport level, measurable quantities. In the process, 1) we identify the relevant transport level quantities, 2) we discuss the tradeoffs between placing the monitors within the VoIP gateways versus placement of the monitors within the transport path, and 3) we identify several areas where further work and consensus within the industry are required. We discover that the relevant transport level quantities are the delay, network packet loss and the decoder's de-jitter buffer packet loss. We find that an in-path monitor requires the definition of a reference de-jitter buffer implementation to estimate voice quality based upon observed transport measurements. Finally, we suggest that more studies are required, which evaluate the quality of various VoIP codecs in the presence of representative packet loss patterns.