What is jitter?

Jitter occurs when there is a delay or deviation in the transmission of data packets. Jitter is common with busy network bandwidth, old network infrastructures, ethernet cables or end devices. It is recommended to carry out regular network testing and upgrade end devices or networks to reduce or even prevent jitter.

The jitter is associated with a flickering screen, a crackling audio transmission crackles and an unreliable zoom video. This due to the variation in frequency when digital signals are being transmitted as well as the variation in runtime when data packets are being transmitted. This means that jitter causes delays, shifts or deviations in signal pulses, amplitudes or phase timing.

In TCP/IP networks, jitter is the deviation in the latency time during the transmission of data packets between participating instances or end devices. This means that data packets will take longer than usual to reach the recipient.

These types of jitter are associated with the following occurrences:

• Constant jitter: There is a fundamental and persistent delay in the transmission of data packets.
• Transient jitter: This is usually caused by individual data packets and results in a brief but noticeable delay in signal transmission.
• Short-term delays: These variations in delay are usually related to changes in transmission routes or congested networks. They are caused by a short-term increase in delays for a certain amount of data packets and can lead to varying delays from packet to packet.

Jitter usually occurs during data transmission between two systems. The packet flow between the systems is delayed constantly or briefly. Latency variation is particularly common in IP networks. Jitter causes a lot of frustration, especially in real-time communications such as video chats, video conferences, and VoIP phone calls. Jitter leads to poor quality communication, noise, crackling, delayed video and audio signals, or fragmented signal transmission. Jitter can also occur in desktop hosting or in virtual VDI infrastructures.

Jitter can happen for a number of reasons and it may vary. The following reasons are most likely:

• Low quality hardware or network infrastructure: Network jitter can occur when outdated routers, modems, computers, cables, switches, or peripherals are used. Signals are delayed during transmission and commands take longer to be carried out.
• Congestion due to low network bandwidth: Depending on the network type or the network protocol, jitter can happen due to network congestion. This can arise if the network doesn’t have enough bandwidth or has too many active devices.
• Wireless networks with poor network connection: A very low transmission rate and a low bandwidth can lead to jitter, especially in wireless networks. Wired network connections are known for better transmission of video and audio signals.
• No prioritization of packets or end devices: If certain data packets or end devices are not prioritized in a network, deviations and delays can occur. This is particularly noticeable in the transmission of audio data in VoIP systems.

The delay or variance in latency can be calculated with several different metrics. The following methods are used for measuring jitter:

The average and minimum round trip time (RTT) are measured using a ping test for voice packets. The RTT is the time required for data packets and signals to reach the receiver from a transmitting instance. Put simply, it is a ping test similar to a ping command or a traceroute.

The delay between intervals when sending and receiving is identified by an instant jitter on individual packets.

Bandwidth tests measure latency variance and delays in data transmission based on network bandwidth or network congestion. The criteria used are upload and download speeds for data packets, jitter times and the network’s bandwidth capacity. Bandwidth tests can be used to determine whether jitter is caused by the ISP. Possible delays can be measured using a theoretical data speed in Kb/s (kilobits per second) or Mb/s (megabits per second). Multiple tests are recommended, as file sizes, line noise, and network and server congestion can affect the tests.

The following tools can be helpful when analyzing and measuring jitter:

• SolarWind’s VoIP/Network Quality Manager: Analyzes and measures call records for packet loss, latency, jitter, and mean opinion scores. Available features include real-time WAN monitoring, VoIP call quality error analysis, visual analysis of VoIP call paths, and monitoring primary rate interface trunks and Cisco VoIP gateways.
• PRTG Network Monitor (Paessler Router Traffic Grapher): Measures and monitors targeted metrics such as switch port data transfer rates, CPU utilization, or occupied memory.
• StarTrinity Continuous Speed Test Tool: Measures network connectivity by monitoring packet loss and jitter by recording packet timestamps. Measured values include upload/download bandwidth, upload/download jitter, packet loss, RTT delays, and downtime.

There are several options to reduce or even prevent jitter:

Buffering stores data packets temporarily before they reach the target source. This mean that applications and services which receive data packets get them from the buffer at a fixed rhythm, which limits delays, temporal fluctuations and deviations. A jitter buffer is used on routers, in networks or on a switch.

Older vintage cables and switches can cause jitter. This is because older ethernet cables can only transmit 125 MHz. Upgrading your Ethernet cable may increase the transmission rate to 250 MHz.

Large updates and upgrades for programs or operating systems can lead to bandwidth and network overload. The leads to your computer not responding or only responding with a long delay. In this case, it is recommended to use the operating system’s scheduler. This ensures automatic updates are scheduled for fixed times during the day when you are not using the device or network.

Applications and activities which are not essential for professional work affect the bandwidth. These include video streams and online gaming. Therefore, unnecessary bandwidth usage should be reduced, especially during work-intensive time windows.

Jitter can be reduced by setting up stable transmission routes in advance and prioritizing traffic or endpoints for data transmission.