Codec parameters for MOS calculation

Overview

MOS - or Mean Opinion Score is a standard for assessing quality of voice communication through subjective (human feedback) or algorithmic methods. More information here.

Cisco Provider Connectivity Assurance (formerly Skylight) supports calculation of synthetic MOS based on ITU-T Wideband E-model G.107.1 pre-2019 (algorithmic) which accounts for wideband codecs such as G.722 AMR and allows for an R-scale up to 129 (MOS 1.0 - 5.0). A later addition to the E-model was presented by ITU-T in 2019 which moves R-scale max to 148 for fullband MOS, this is not supported in Skylight.

MOS (and R) is reported for TWAMP, UDP- and ICMP echo sessions generated by the following actuators:

• Cisco Provider Connectivity Assurance Sensor Control (formerly Skylight sensor: control) locally generated (i350 PCI-passthrough or through vSwitch)
• Cisco Provider Connectivity Assurance Sensor SFP (formerly Skylight sensor: SFP compute) NFV-PM
• Cisco Provider Connectivity Assurance Sensor Agents (formerly Skylight sensor: agents) actuate

For the Sensor Control and Sensor SFP sessions, the settings for MOS codec calculation is done on sensor orchestration capabilities within Provider Connectivity Assurance (formerly Skylight orchestrator), globally for all sessions on the system. The default codec emulation is G.711.

For Agents, the settings are configurable per-session, with default again being G.711. The parameter setting UI can be seen in the screenshot below - MOS loss robustness factor and MOS equipment impairment factor

Codec variants and their Impairment parameters

Use the table below to find suitable values for loss robustness and equipment impairment based on the codec variant that should be emulated.