Cisco Cisco Prime Collaboration Assurance 11.5 White Paper

 

 

© 2016 Cisco and/or its affiliates. All rights reserved. This document is Cisco Public Information. 

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White Paper 

Cisco Prime Collaboration Assurance and 
Analytics: Grade VoIP Calls using SCSR Instead of 
MOS 

Mean opinion score is no longer the best way to grade audio quality. Concealment-
related metrics with Cisco Prime

™

 Collaboration Assurance and Analytics offers many 

advantages including simplicity, better SLA enforcement, and codec independence. 
This white paper explains the rationale behind replacing MOS with new call-quality 
metrics. 

Cisco Prime Collaboration Assurance and Analytics uses mean opinion score (MOS, including Cisco

®

 Voice 

Transmission Quality [Cisco VTQ] and the K-Factor algorithm) reported by IP phones to grade listener audio 

quality. The latest Cisco IP Phones (Cisco DX Series and Cisco IP Phone 7800 and 8800 Series devices) as well 

as future IP phones no longer report MOS. In addition to the reason for changing how we measure call quality, this 

document explains: 

● 

The advantages of using concealed seconds (CS) and severely concealed seconds (SCS) metrics, a 

process that is more efficient and reliable on a typical enterprise environment 

● 

Usage of SCS Ratio (SCSR) (explained later) in Cisco Prime Collaboration Assurance and Analytics to 

grade audio quality 

To enhance end-user experience, many Cisco IP Phones support wideband audio codecs (such as G.722, 

AAC-LD, and up-coming Opus). With this transition, MOS scores are no longer optimal to grade call quality: 

● 

MOS scores don't scale to wideband codecs. 

● 

The value of MOS scores is codec-dependent. 

● 

Wideband code uses the same algorithm as low-band code, but at an incompatible scale. A great, 

unimpaired wideband G.722 call will score lower than a corrupted, narrowband 711 call. 

● 

“Average MOS” over a 2-hour call has little or no meaning. Long calls will have an underweighted MOS 

score, short calls overweight. 

● 

The MOS score is not ideal for service-

level agreement (SLA) enforcement because MOS scores can’t be 

added or averaged across calls of different duration or codecs. 

Because of the nature of voice over IP (VoIP), loss and jitter are inevitable. If for any reason an IP phone doesn't 
have valid audio to play, packet lost concealment (PLC) is used to smoothly fill in the gap with “made-up” audio. 

Concealment statistics measure packet (frame) loss and its effect on voice quality in an impaired network. 

All Cisco IP Phones report the following concealment-related metrics (refer to Table 1 and the call detail record 
(CDR) and call management record (CMR) administrator’s guide, for example, at: 

.