> For the complete documentation index, see [llms.txt](https://prosbcdocs.telcobridges.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://prosbcdocs.telcobridges.com/appendices/appendix-a-glossary/glossary-mean-opinion-score-mos.md).

# Glossary: Mean Opinion Score (MOS)

Mean Opinion Score (MOS) rates voice call quality from 5 excellent to 1 bad, with ideal MOS of 4.3 for G.711, 4.0 for G.729 and 3.6 for G.723.

### TelcoBridges and MOS

Toolpack uses a well-known model to evaluate a MOS value based on collected statistics for a call. There are 3 factors that significantly impact the call quality: latency, packet loss and jitter of RTP packets. Using these statistics, we calculate an R-value that ranges from 1 to 100 where a higher number is better. Finally the MOS is calculated using this formula.

\
MOS = 1 + 0.035R + ((R - 60) \* (100 – R) \* 0.000007R)

#### TelcoBridges' MOS Implementation

For the MOS calculated from the R-value, there is no notion of codec. We decided to apply a ratio in relation to the codec's ideal MOS.

See the table below:

| R-Value  | Calculated MOS | Network quality | G.711   | G.729   | G.723   |
| -------- | -------------- | --------------- | ------- | ------- | ------- |
| 25       | 1.42           | 32.11           | 1.38    | 1.28    | 1.16    |
| 50       | 2.58           | 58.40           | 2.51    | 2.34    | 2.10    |
| 75       | 3.82           | 86.68           | 3.73    | 3.47    | 3.12    |
| 80       | 4.02           | 91.26           | 3.92    | 3.65    | 3.29    |
| 85       | 4.20           | 95.21           | 4.09    | 3.81    | 3.43    |
| 90       | 4.34           | 98.41           | 4.23    | 3.94    | 3.54    |
| **93.2** | **4.41**       | **100**         | **4.3** | **4.0** | **3.6** |

The final row is the **codec ideal MOS**: the highest MOS each codec can reach on a perfect network, where the R-value is 93.2 and network quality is 100%. G.711 tops out at 4.3, G.729 at 4.0 and G.723 at 3.6.

**Network quality**

TelcoBridges' MOS implementation adds another concept over the standard MOS: Network quality. The network quality parameter provides a fast way to identify a bad network condition. The MOS is useful when comparing calls for the same [NAP](/appendices/appendix-a-glossary/glossary-nap.md) or for the same network. But if you are using several codecs, the MOS value might be misleading to detect network problems.

* Examples:
  * A perfect network (i.e. no packet loss, no latency) using G.723 will have a MOS of 3.6. This is relatively low, but it represents a network quality of 100%. The only way to improve the MOS will be to use a higher quality codec.
  * On the other hand, a G.711 call with a MOS of 3.7 represents a network quality of 86%. This rather low and based on these values, you know there is something that can be improved in the network.

**Ingress-Egress**

There are 2 MOS values calculated per call leg. The ingress value is using RTP reception statistics and the egress value is using RTCP statistics received from the peer. Using these statistics, w can calculate MOS and network quality for the ingress and egress directions.

When using Call Trace, the lowest value between ingress and egress MOS and network quality are displayed.

### Related subject

* [MOS scores in CDRs](https://prosbcdocs.telcobridges.com/configuration-details/configuration-by-web-portal-category/call-detail-records-cdr/radius-cdrs/radius-cdr-attributes)
  * [Statistics in the CDRs](/configuration-details/configuration-by-web-portal-category/call-detail-records-cdr/cdr-variables/call-statistics-available-in-cdr.md)
* [MOS in routing scripts](https://docs.telcobridges.com/wiki/Routing_script_tutorial:Mini_Development_Guide#Script_parameters_protocol_mapping)


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