Real-Time Monitoring – MOS Score Monitoring
Realtime flows may be monitored for their quality and user experience. Mean Opinion Score (MOS) is a well-known derived metric used for this purpose. MOS is used to represent the user experience of the audio, video, and voice applications – it is a measure of the quality of the voice and video data traffic.
A MOS Score of 5 is Excellent and a score of 1 is very poor. Network impairments such as loss, jitter, delay over a link between clients affects the MOS of realtime applications. In addition to network conditions, the codec used can also affects the MOS. Therefore, for the same network conditions between two end points, MOS can differ between codecs and vice versa. RealTime Flow Monitoring enables processing and computation of MOS scores on Audio, Video and Voice traffic.
In Versa VOS, we can define an acceptable MOS score in a SLA profile and associate it with a SD-WAN traffic steering policy.
The APPID engine intercepts the RTP flow and sends a copy of the packet to the RealTime Monitoring (RTM) engine for MOS computation. The RTM process the stream to identify the codec, delay, loss and jitter to calculate the MOS value. All these computations are done in real time. The way this is integrated is in such a way that it does not add a noticeable overhead to the system load or performance.
VOS supports about 200 audio, video and voice codes.
Configuration
Objectives:
A. Enable Real-Time Monitoring
B. Verify the MOS Scoring on the analytics
Real-time monitoring can be accessed from the ‘Others’ tab under Configuration.
Step 1: Enable Real-time Monitoring and define the Reporting Interval
The reporting interval can be anywhere from 1 to 65535 with a default value of 2 seconds. Setting this to a higher value might result in VOS being less reactive to changing network conditions.
Verification
The MOS score can be viewed on the Analytics as well as CLI.
In the Analytics, MOS score can be viewed from the SDWAN Menu under SDWAN > Sites > MOS
The output shows the active sessions for which the MOS is being evaluated and the detailed session shows the MOS score.
admin@PocGW-cli> show orgs org-services PoC-Org sd-wan path mos-score PoC-Office REMOTE BRANCH LOCAL CIRCUIT REMOTE CIRCUIT CODEC MOS ------------------------------------------------------------- PoC-Office DIRECT-INTERNET DIRECT-INTERNET Silk WB 4.09
The CLI output above shows the MOS score of a particular branch against a CODEC.
Summary
In this article we saw how to enable RealTime Monitoring on VOS and how they system evaluates and produces MOS scores. The MOS scores can also be tied to an SLA-Profile to enable path switching based on this and hence, ensuring consistent application experience for the users.
