Jitter Test

What causes high jitter?

Jitter refers to intermittent delays in data packet transmission. This delay, measured in milliseconds, can negatively impact the quality of real-time applications like VoIP communication, streaming, and online gaming. Jitter shouldn’t be confused with network latency, which is the speed of your network traffic measured in milliseconds. 

Jitter causes packets to be delivered at irregular intervals. A few packets might be sent with a small delay and then several packets might be sent all at once. This causes packet loss, which then causes a decline in the quality of real-time service.

If you’re using VoIP in your network, you are bound to have some packet loss and jitter—most of the time it won’t have a lasting effect on your connectivity. However, jitter can become a problem when it exceeds a certain level. The following are acceptable levels:

• Jitter below 30ms, ideally below 20ms
• Less than 1% packet loss
• Overall network latency less than 150ms

When you have high jitter levels over 30ms, you’ll notice a difference in VoIP call quality. Your calls might be distorted, warbled, or cut in and out. 

Without conducting a jitter test, the exact cause of high jitter can be difficult to determine, especially in a large enterprise. However, since jitter is most commonly experienced during voice calls, internet connection issues are presumed responsible for most instances of jitter. The three most common causes of poor internet connection, and high jitter, are:

1. Network congestion: Network congestion is by far the most common (and most obvious) cause of high jitter. If there are too many devices vying for bandwidth on the same network at the same time, your internet connection will slow to a crawl. Packets get dropped or delivered out of order, which causes jitter.
2. Wireless networks: Wi-Fi is convenient and increases mobility in an enterprise, but it’s not always strong or stable enough to sustain clear video calls. What’s more, Wi-Fi connections are infamous for packet loss. With so many packets traveling through the air, it’s easy for some to get lost and cause jitter.
3. Old or faulty hardware: An outdated modem, old or damaged Ethernet cable, or misconfigured router can all weaken your internet connection and cause jitter. 

If the internet connection isn’t the problem, high jitter can also be caused by poor packet prioritization. Packet prioritization is a kind of Quality of Service (QoS) setting that allows you to prioritize certain kinds of network traffic, so they receive the most bandwidth, reducing network congestion. If your packets aren’t prioritized appropriately, business critical operations might not receive enough network resources to function efficiently. 

How do I reduce jitter?

Jitter cannot be eliminated for good, but it can be reduced. These are the top five ways to reduce jitter in your network:

1. Use a jitter buffer: A jitter buffer is a tool designed to combat jitter by temporarily storing incoming packets before sending them through to their destinations. This helps ensure packets arrive in sequence. Jitter buffers are preconfigured to buffer traffic for 30-200ms before releasing the packets.
2. Upgrade your internet connection: One of the best things you can do to prevent jitter is upgrade to a high-speed internet connection. Make sure you have robust upload and download speeds that can handle VoIP calls. You should upgrade your network hardware as well.
3. Use an Ethernet cable: You can also reduce jitter by opting for an Ethernet or fiber-optic cable connection over Wi-Fi. Connecting directly to the router can dramatically improve voice call quality and overall experience. 
4. Reconsider your bandwidth usage: In a large enterprise, it’s important to make sure your bandwidth is being used as effectively as possible. To reduce jitter and reserve bandwidth for business-critical operations, restrict unnecessary usage during work hours. You can also set applications and devices to update outside of work hours, so more resources will be free during the day. 
5. Optimize your network settings: Similarly, QoS settings can help you make sure your resources are being allocated properly. Reduce jitter by configuring your network to prioritize VoIP and video traffic before anything else.

These troubleshooting techniques can be effective for combatting jitter when you suspect you have it somewhere in your network. However, a jitter test tool can help you figure out exactly where the jitter is occurring, and to what extent. 

How to test jitter

A jitter test is a kind of network performance test to help you identify how much jitter is in your network by offering greater insight into how quickly packets are successfully reaching their destinations. 

A network jitter test observes network traffic, specifically packet delivery times, to evaluate the differences in time taken to deliver packets. A network jitter test is usually done by connecting a computer to an external server and then passing data packets between them, after which the transmission will be tested, measured, and analyzed by a jitter test tool for jitter. There are also “plug-and-chug” third-party services available to calculate jitter for you.

How a jitter test measures jitter depends on how many endpoints your network has control over. If your network has control over a single endpoint, jitter is measured by taking the average of the minimum round-trip time (RTT) and the RTT of a series of voice packets. If your network has control over double endpoints, the jitter measured is instantaneous jitter, the difference between the transmission and receipt of the packet. This variation of a jitter test measures the difference between average instantaneous jitter and the instantaneous jitter occurring during the transmission of a series of voice packets.  

A ping jitter test is another way to test for jitter. A ping jitter test measures the amount of delay, in milliseconds, before sending and receiving packets from one endpoint to another. In the context of VoIP, this test would measure how long it will take your voice to reach the recipient on the other end of the call. 

Why is jitter testing important?

Jitter testing is important because it’s the most accurate way to determine how much jitter is affecting your network and to what extent. 

Many end users rely on voice calls and streaming services that require a lot of bandwidth. In most cases, a little jitter is nothing to be alarmed about, but for real-time applications, tiny glitches can mean the difference between success and failure.

When you make a voice call, your voice is broken down into millions of data packets which are then transmitted over the internet to the caller on the other end. As your segmented voice data travels, it is in competition with all the other network traffic occurring at the same time. This can wear down resources and eat up bandwidth, causing jitter and delays. 

The difference between delayed VoIP packets and delayed email packets, for instance, is that email packets can be reassembled right before final transmission to their destination. VoIP calls cannot be reassembled in time, causing your voice to sound choppy and out of sequence. This also applies to video calls and online gaming.  

In short, when it comes to VoIP conversations, anything less than real-time signal delivery can cause dropped calls, crackling reception, and indecipherable audio signals. Jitter tests are your greatest defense against this. Executing a jitter test can help you quickly pinpoint jitter within your network and mitigate its effects before it starts to affect end users.

How do jitter tests work in SolarWinds VNQM?

SolarWinds VoIP & Network Quality Manager is an enterprise-grade jitter test tool designed to help network administrators mitigate and manage jitter in their networks. While using a high-quality network monitoring tool can also allow you to gain visibility into jitter, the specialized tools in VNQM have features built to specifically monitor and provide deeper performance visibility into VoIP conversations.

VNQM is designed to monitor the most important VoIP call quality metrics like jitter, latency, and packet loss. In addition to tracking these metrics, VNQM can also notify you when jitter is detected. You can also set custom alerts to sound whenever jitter exceeds any number of predefined parameters, which can allow you to begin troubleshooting quicker. Additionally, the exclusive SolarWinds PerfStack feature can allow you to correlate jitter with other performance metrics in your network, which can empower you to take a holistic approach to improving overall VoIP performance.