How to Measure VoIP Quality & MOS Score (Mean Opinion Score)

Are you tired of constantly dropping calls or struggling to hear your loved ones on the other end of the line? Fear not, because we're here to talk about the one thing that can make or break your VoIP experience: MOS score. No, we're not talking about the fuzzy creature from Star Wars - we're talking about the Mean Opinion Score, the nifty little metric that can help you measure and improve the quality of your VoIP calls.

VoIP Quality is highly reliant on network performance, which means that many network problems like packet loss, latency, and jitter can cause high levels of VoIP degradation. To avoid embarrassing choppy voice calls, or lagginess during your next client meeting, we’re running you through how to measure VoIP Quality with MOS Score (Mean Opinion Score).

So grab a cup of coffee, settle in, and let's dive into the wonderful world of MOS scores and VoIP quality!

VoIP Quality refers to the overall level of audio and visual performance experienced during a Voice over Internet Protocol (VoIP) call. This includes factors such as call clarity, signal strength, delay, echo, and other audio and visual distortions that can impact the user experience.

VoIP Quality can be influenced by a variety of factors, including the quality of the internet connection, the type of device used for the call, and the network infrastructure supporting the call. Measuring and monitoring VoIP Quality is important to ensure that users are able to communicate effectively and efficiently, without experiencing frustrating audio or visual interruptions.

VoIP Quality is typically measured using a combination of objective and subjective metrics. Here are some common methods for measuring VoIP Quality:

1. MOS score: The Mean Opinion Score (MOS) is a subjective metric that is obtained by having a group of people rate the quality of audio samples. MOS scores are widely used in the telecommunications industry to assess the quality of VoIP calls. We'll expand on MOS Score in the next section.
2. R-factor: The R-factor is an objective metric that is used to measure the quality of VoIP calls. It takes into account factors such as delay, jitter, and packet loss to produce a score between 0 and 100. A higher R-factor indicates better call quality.
3. Packet loss rate: Packet loss rate is the percentage of voice packets that are lost during transmission. A higher packet loss rate can result in poor call quality.
4. Jitter: Jitter is the variation in delay between packets. High jitter can result in poor call quality.
5. Latency: Latency is the delay that occurs between the time when a voice packet is sent and when it is received. High latency can result in poor call quality.
6. Echo: Echo occurs when a caller hears their own voice back in their earpiece. Echo can be caused by network delays, poor echo cancellation, or other factors, and can result in poor call quality.

By measuring these metrics, VoIP service providers can identify areas where call quality needs improvement and take steps to improve the overall quality of their services.

The Mean Opinion Score, usually referred to as MOS Score, has been the most commonly-used metric to measure the overall voice call quality for decades. Standardized by the International Telecommunications Union (ITU-T), MOS Score refers to:

A numerical measure of the human-judged overall quality of voice and video sessions.

The MOS is obtained by having a group of people listen to a set of standardized audio samples and rate them on a scale of 1 to 5, with 1 being the lowest quality and 5 being the highest. The ratings are then averaged to obtain the MOS score.

The MOS score is widely used in the telecommunications industry to measure and monitor the quality of voice calls, including VoIP calls. By measuring MOS scores, telecom companies can identify areas where call quality needs improvement and take steps to improve the overall quality of their services.

Voice Quality MOS Score is most often judged on a scale from 1 (bad) to 5 (excellent) of the perceived quality of a voice call. Although originally Mean Opinion Scores were derived from surveys of expert observers, today a MOS Score is often produced by an Objective Measurement Method approximating a human ranking.

The MOS Score (Mean Opinion Score) for Voice Quality was originally developed for traditional voice calls but has been adapted to Voice over IP (VoIP) in the ITU-T PESQ P.862.

The standard defines how to calculate MOS Score for VoIP Quality based on multiple factors such as the specific codec used for the VoIP call. Each VoIP codec (ex: G.711, G.722, G.723.1, G.729) behaves differently. Some codecs such as G.711 are uncompressed for higher quality but use more bandwidth than compressed codecs such as the G.729.

The MOS Score we measure is for the G.711 codec, which is by far the mostly used codec for VoIP calls. The maximum MOS Score for a G.711 call is 4.4.

When deciding how we would be measuring VoIP Quality in the Obkio app, we decided to measure it based on the MOS Score. Here are the details for how we measure VoIP MOS Score. The table below lists the different qualities and the lowest MOS Score limit for each of them. The limit values are from the ITU-T standards.

We also realized that most of our customers were not very familiar with the MOS Score and the interpretation of MOS in VoIP Quality. To help all our users understand more easily, we redesigned the MOS Score graph to create the VoIP Quality graph.

Obkio’s MOS VoIP Quality graph categorizes, for every minute, the MOS Call Quality as

• Best
• High
• Medium
• Low
• or Poor

The exact MOS Voice Quality Score is always available in the graph tooltip.

This feature is a great measure of the Quality of Experience (QoE) for users using VoIP applications over their network and helps IT Pros evaluate the impact of Network Performance on VoIP Applications.

VoIP issues make up 50% of IT problems!

VoIP travels a long distance from your network, through the Internet, and up to your Service provider. That means that, when a problem occurs, no matter where it is, you need to manage it.

A VoIP monitoring tool is the best way to ensure accurate and continious VoIP Quality measurement - and Obkio Network Performance Monitoring software can help with that.

Obkio is a Network Monitoring and Troubleshooting tool with it's own VoIP Monitoring feature.

Network performance can have a significant impact on VoIP Quality. When making a VoIP call, the voice data is transmitted over the internet, and any issues with the network can cause delays, packet loss, and other disruptions that can affect call quality. Which is why it's important to monitor network and VoIP Quality all together.

Obkio's VoIP Monitor measurse VoIP Quality with MOS Score and start to proactive identify and troubleshoot VoIP issues before your users even know they exist!

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To monitor VoIP Quality in all your network locations, for all your core VoIP apps, you need to deploy Network Monitoring Agents which continuously measure network performance in key network locations like offices, data centers and clouds.

The Agents exchange synthetic traffic between each other to measure core network metrics that are essential to VoIP Quality, like MOS score.

To collect the data you need to translate, you’ll need:

• Local Agents: Installed in the targeted office location experiencing VoIP Quality issues. There are several Agent types available (all with the same features), and they can be installed on MacOS, Windows, Linux and more.
• Public Monitoring Agent: These are deployed over the Internet and managed by Obkio. They compare network and VoIP performance up to the Internet and can be used to monitor VoIP Quality for apps like Microsoft Teams and Zoom. They can also help identify if the network and VoIP issue is global or specific to a destination.

As we explained earlier, a tool like Obkio will automatically measure your VoIP Quality for you! Once your Monitoring Agents are deployed, they will start exchanging synthetic traffic to measure VoIP Quality.

Obkio’s MOS VoIP Quality graph categorizes, for every minute, the MOS Call Quality as

• Best
• High
• Medium
• Low
• or Poor

Once you’ve deployed Obkio Monitoring Agents in your key network locations, they will start measuring other key network metrics that essential to your network and VoIP performance.

Here are some metrics you can measure with Obkio that are detrimental to VoIP Quality:

Here are some ways that network performance can affect VoIP Quality:

1. MOS score: As discussed earlier, the Mean Opinion Score (MOS) is a subjective metric that is used to assess the quality of human speech and other forms of audio. MOS scores can provide an overall measure of VoIP Quality and can help identify areas where call quality needs improvement.
2. Bandwidth: VoIP calls require a certain amount of bandwidth to maintain call quality. If the network is congested or there is not enough bandwidth available, the call quality may suffer.
3. Latency: Latency is the delay that occurs between the time when a voice packet is sent and when it is received. High latency can cause a delay in the conversation, making it difficult to communicate effectively.
4. Jitter: Jitter is the variation in delay between packets. High jitter can cause the voice quality to degrade, resulting in a choppy or garbled conversation.
5. Packet loss: Packet loss occurs when voice packets are dropped during transmission. Even a small amount of packet loss can result in poor call quality and affect the ability to understand the conversation.

To ensure high-quality VoIP calls, it is important to have a network that is capable of handling the required bandwidth and has low latency, jitter, and packet loss. Network monitoring and optimization can help identify and resolve any issues that may be affecting VoIP Quality.

With this setup, you now have everything you need to identify and troubleshoot VoIP Quality issues. Obkio will automatically alert you of any VoIP performance degradation, MOS score changes, and VoIP Quality issues.

Here are some common VoIP Quality issues you may encounter There are several common VoIP quality issues that can affect the user experience. Here are some of the most common VoIP quality issues:

• Jitter: High jitter can result in choppy or distorted audio, which can make it difficult to understand the conversation.
• Latency: High latency can cause delays in the conversation, making it difficult for users to have a natural conversation.
• Packet loss: High packet loss can result in gaps in the conversation, making it difficult to understand what is being said.
• Echo: Echo occurs when a user hears their own voice after speaking. This can be distracting and make it difficult to concentrate on the conversation.
• Noise: Noise can occur due to a variety of factors, such as network interference or equipment issues. This can make it difficult to understand what is being said and can be very distracting.
• Call drops: Call drops occur when a call is unexpectedly disconnected. This can be frustrating for users, especially if it happens frequently.
• Poor call setup time: Poor call setup time can make it difficult for users to make and receive calls quickly, leading to a poor user experience.

By identifying and addressing these common VoIP quality issues, VoIP service providers can improve the user experience and ensure that their systems deliver high-quality audio that meets the expectations of users.

When it comes to VoIP quality, there's a big difference between crystal-clear calls and garbled, robotic-sounding conversations. To help you distinguish between the two, we're breaking down what constitutes good VoIP quality versus bad.

Good VoIP quality is generally considered to be when voice calls are clear and have a natural sound that is similar to a traditional phone call. In general, good VoIP quality is characterized by the following:

• High MOS score: A MOS score of 4 or above is generally considered good VoIP quality.
• Low packet loss: A packet loss rate of less than 1% is generally considered good VoIP quality.
• Low jitter: Jitter of less than 30 milliseconds is generally considered good VoIP quality.
• Low latency: Latency of less than 150 milliseconds is generally considered good VoIP quality.

On the other hand, bad VoIP quality is characterized by poor audio quality that is often characterized by the following:

• Low MOS score: A MOS score of less than 3 is generally considered poor VoIP quality.
• High packet loss: A packet loss rate of more than 5% is generally considered poor VoIP quality.
• High jitter: Jitter of more than 50 milliseconds is generally considered poor VoIP quality.
• High latency: Latency of more than 300 milliseconds is generally considered poor VoIP quality.

Ultimately, what constitutes good or bad VoIP quality can depend on individual users' expectations and preferences. However, the general guidelines above can provide a useful benchmark for evaluating VoIP quality.

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So we now know that a high MOS score means that you have great VoIP Quality! But what is considered a high MOS score rating?

MOS (Mean Opinion Score) measures the perceived quality of VoIP audio on a scale from 1 to 5, with 5 being the best possible score. A high MOS rate indicates that the audio quality is good, while a low MOS rate indicates poor audio quality.

In general, a MOS score of 4 or above is considered to be high-quality audio and indicative of a good VoIP experience. This means that users perceive the audio quality to be similar to that of a traditional phone call.

On the other hand, a MOS score of less than 3 is considered to be low-quality audio and indicative of a poor VoIP experience. This means that the audio quality is distorted, choppy, or robotic-sounding, making it difficult for users to understand the conversation.

Overall, aiming for a high MOS rate is important for delivering a good VoIP experience and ensuring that users are satisfied with the audio quality of their calls.

When it comes to measuring the performance of any technologies or application, the user-perspective is your most important metric. Users identify good performance because essentially, good performance is the ability to meet a user’s expectations.

Quality of Experience (QoE) is a metric that allows you to measure performance from the end-user perspective to gain a better understanding of human quality metrics and be able to actually measure whether performance met a user’s expectations.

QUALINET (The European Network on Quality of Experience in Multimedia Systems and Services), describes QoE as:

“The degree of delight or annoyance of the user of an application or service. It results from the fulfillment of his or her expectations with respect to the utility and / or enjoyment of the application or service in the light of the user’s personality and current state.”

QoE allows you to measure the user’s perception of the effectiveness and quality of a system or service to essentially give you a performance standard. In fact, users base their opinions about the network exclusively on their perception of QoE.

QoE and VoIP Quality are two metrics that really work hand-in-hand. You can actually use VoIP Quality as a way to measure QoE, because after all, if poor VoIP Quality is leading to choppy calls, and robot voices, you can be pretty certain that your user is not having a pleasant experience.

Nowadays, IP networks are used to transport various types of applications which are a lot more sensitive to network performance and quality. One of those applications is VoIP.

This is why network engineers implement QoS (Quality of Service) to prioritize some traffic on the network in order to reduce latency, jitter and packet loss. In case of a network congestion, this will ensure that performance sensitive applications are always running without degradation and that only the less critical applications (such as web browsing) are impacted.

QoS (Quality of Service), is important for all VoIP Quality, because, at some point, voice and data will ‘mix’ on your network, or on the Internet. VoIP Call Quality can be measured using a variety of metrics, but it is more so perceived in regard to clarity of the voice quality heard at both ends of a call. The human ear is very sensitive, and will pick up on anything that may sound abnormal.

QoS allows us you set different priorities for different types of data Services on your network. To ensure that phone calls are good quality, we need to give VoIP traffic a higher priority than, for example, a download of a Windows 10 upgrade. That way, even with several computers doing upgrades on your network, calls are still crystal-clear.

VoIP Quality is about being able to get high-fidelity audio at each end of the phone call, without unwanted distortions. VoIP QoS will be affected by:

• Bandwidth
• Packet Loss
• Jitter
• Latency

Obkio allows you to continuously monitor QoS with DSCP features - specifically the DSCP code located in the IP header.

QoS (Quality of Service) for MOS (Mean Opinion Score) refers to the ability of a VoIP system to deliver high-quality audio that meets the expectations of users. QoS for MOS is typically achieved through a combination of network design, equipment selection, and network management practices.

To achieve QoS for MOS, VoIP service providers may implement various strategies, such as:

1. Prioritizing voice traffic over other types of network traffic to ensure that voice packets are given priority over data packets.
2. Implementing Quality of Service (QoS) mechanisms such as traffic shaping, traffic policing, and traffic prioritization to manage network traffic and ensure that voice packets are delivered with minimal delay, packet loss, and jitter.
3. Selecting high-quality VoIP equipment such as routers, switches, and IP phones that are designed to handle the demands of VoIP traffic.
4. Monitoring network performance using tools such as network monitoring tools like Obkio, network analyzers, packet sniffers, and other monitoring tools to identify issues that could affect call quality and take corrective actions.

By implementing QoS strategies, VoIP service providers can ensure that their systems deliver high-quality audio that meets the expectations of users, as reflected in MOS scores. This can lead to improved user satisfaction, better business outcomes, and increased customer loyalty.

When looking at how to calculate MOS Score, network metrics give you the most value and detail when they’re combined to give you a full overview.

Network Device Monitoring is a feature that allows you to monitor the performance of networking devices such as firewalls, routers, switches and wifi access points is crucial for IT teams.

The Device Monitoring feature inside the Obkio Software is a fast and easy solution to get detailed information about the health of devices using Ultra-Fast Polling (every 30 seconds).

Along with Device Monitoring, using a complete end-to-end Network Monitoring tool, monitoring VoIP MOS Score with Obkio’s Network Monitoring solution and Network Device Monitoring allows you to truly understand VoIP Quality from the end-user perspective.

Obkio measures performance from the end-user perspective by monitoring synthetic traffic (with no packet capture required) every 500ms!

This allows you to perform a network assessment of your entire network infrastructure to identify exactly:

1. What network problems?: It’s important to find out what network problems are affecting VoIP Quality to be able to begin network troubleshooting. As I mentioned earlier, there are a variety of network problems that can affect VoIP performance, such as packet loss, jitter, and bandwidth.
2. Where problems are located: Modern networks are vast infrastructures that can span over a variety of locations. When a problem arises, it is important to pinpoint where VoIP issues are located along your network so you know where to focus your troubleshooting efforts.
3. Who the owner of the problem is: Your business may only have one IT specialist, or you may have a large IT department with different employees responsible for different parts of the network. Identifying who is responsible for dealing with a problem affecting VoIP Quality (user, application, network, or ISP), will help you decide who is responsible for fixing it.
4. How to solve problems: Once you’ve collected all the information from the three previous points, you can assess the data to come to a resolution. It’s a given that having as much information as possible will lead to a quick and efficient solution.

You can check out the Network Performance Monitoring case study with Station 22, an international beverage manufacturer and distributor, to find out how they pinpointed undetected network problems on their firewall using MOS Score, Network Performance Monitoring, and Network Device Monitoring.

He’s a little summary about their problem and their solution.

Station 22 began experiencing VPN network application slowness and instability for their Microsoft Teams and GoToMeeting application.

Using Obkio’s Network Performance Monitoring software, they identified that their network latency was constant but the packet loss kept increasing. Specifically, there was a lot of packet loss occurring over the Internet as the bandwidth usage increased during the day, likely due to increased activity from users. They pinpointed the exact percentage of packet loss in the Obkio app with the graph tooltip.

They looked into the MOS Score chart to find that it reported thresholds well above what is normally acceptable.

Finally, they moved to Obkio's Network Device Monitoring feature on their firewall and saw that the CPU usage was well above the 40% threshold shown on their Firewall's GUI.

By using all three features, Station 22 was able to get a complete overview of all of the metrics affecting their network performance, and realized that the type of problem they were facing was known and could be fixed with a firmware update of the firewall. They immediately performed emergency maintenance and the problem was resolved in no time.

Congratulations, you're now a VoIP quality measuring expert! By understanding the metrics and factors that contribute to VoIP quality, such as MOS score, packet loss, jitter, and latency, you're well-equipped to diagnose and troubleshoot any issues that arise with your VoIP system.

Network performance, specifically VoIP Quality, can be affected by a variety of different factors, which is why it’s important to get a complete, end-to-end overview of all these factors to truly understand what is wrong, and how to fix it.

Whether you're a business looking to improve your customer service or an individual seeking a high-quality VoIP experience, these tools and tips will help you ensure that your calls are crystal-clear and enjoyable. So go forth, make some VoIP calls, and experience the magic of high-quality audio!

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