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• Low quality hardware or network in­fra­struc­ture: Network jitter can occur when outdated routers, modems, computers, cables, switches, or pe­riph­er­als are used.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.