What is Jitter? Jitter happens when incoming data packets are delayed and don’t show up at the expected time or in the expected order. When data is transmitted over the Internet it is broken into small packets. A typical packet is approximately 1,000 bytes or 0.001 megabytes. This means a lot of packets are sent to your home computer for even basic web transactions.
Packets are created at the location originates a web signal. This might be a site that is streaming a video, sending a file, completing a voice over IP call, or letting you shop online. The packets are sent in the order that the original data stream is encoded. Each packet takes a separate path across the Internet. Some packets arrive quickly, while others are delayed for some reason. Measuring jitter means measuring the degree to which packets end up at your computer late or in the wrong order.
Why Does Jitter Matter? Jitter matters the most when you are receiving packets for a real-time transaction like a streaming video, a Zoom call, a voice over IP call, or a video connection with a classroom. Your home computer is going to do its best to deliver the transmissions on time, even if all the packets haven’t arrived. You’ll notice missing packets of data as pixelation or fuzziness in a video, or as poor sound quality on a voice call. If enough packets are late, you might drop a VoIP call or get kicked out of a Zoom session.
Jitter doesn’t matter as much for other kinds of data. Most people are not concerned if it takes slightly longer to download a data file or to receive an email. These transactions don’t show up as received on your computer until all (or mostly all) of the packets have been received.
What Causes Jitter? The primary cause of jitter is network congestion. This happens when places in the network between the sender and the receiver are sent more data packets than can be processed in real time.
Bandwidth constraints can occur anywhere in a network where there is a possibility of overloading the capacity of the electronics. The industry uses the word chokepoint to describe any place where data can be restricted. On an incoming data transmission, an ISP might not have enough bandwidth on the incoming backbone connection. Every piece of ISP network gear that routes traffic within an ISP network is a potential chokepoint – a common chokepoint is where data is handed off to a neighborhood. The final chokepoint is at the home if data is coming in faster than the home broadband connection can handle it.
A common cause of overloaded chokepoints is old or inadequate hardware. An ISP might have outdated or too-small switches in the network. The most common chokepoints at homes are outdated WiFi modems or older computers that can’t handle the volume of incoming data.
One of the biggest problems with network chokepoints is that any time that an electronics chokepoint gets too busy, packets can be dropped or lost. When that happens, your home computer or your ISP will request the missing packets be sent again. The higher the jitter, the more packets that are lost and must be sent multiple times, and the greater the total amount of data being sent through the network. With older and slower technologies like DSL, the network can get paralyzed if failed packets accumulate to the point of overwhelming the technology.
Contrary to popular belief, faster speeds don’t reduce jitter, and can actually increase it. If you have an old inadequate WiFi modem and upgrade to a faster technology like fiber, the WiFi model will be even more overwhelmed than it was with a slower bandwidth technology. The best solution to lowering jitter is for ISPs and customers to replace equipment that causes chokepoints. Fiber technology isn’t better just because it’s faster – it also includes technology that move packets quickly through chokepoints.