by Charles Miller

A customer who bought a new High Definition smart TV was understandably disappointed when it constantly buffered, froze, coughed, stuttered, and wheezed whenever he tried to watch streaming content. The TV manufacturer said he should contact his Internet Service Provider (ISP). The ISP said his internet connection was fine. That was when he asked me to help him prove to the store that his new TV was defective. A defective TV was not the first thing I suspected.

It did not take me long to look over his Local Area Network (LAN) which consisted of one modem provided by his ISP, one Wi-Fi router, computers, smart phones, printer, televisions, Amazon Alexas, and a few household appliances. He assured me that everything worked "perfectly" and proudly showed me an internet speed test on his smart phone to (allegedly) prove that he could connect at a speed of over 200 MBps.

There was an obvious problem with that number. His router was a venerable old Linksys model WRT54G version 1, which I happen to know was discontinued in 2005. It is a testament to the quality of Cisco Linksys products for that old router to still be working well after two decades, but I knew that its maximum speed was only 100 MBps, so that speed test showing the internet speed to be over 200 MBps was obviously an illusionary estimate.

The customer demanded to know why everything was working so perfectly, except for the new television. I explained that internet speed was not the only consideration, and that because of his old router and the many devices connected to it that the problem was likely to be "jitter."

"What's jitter?" he demanded. I answered: "when of packets is order out jitter received are." "What???" he asked. So I repeated "of received order jitter are when out packets is." He was still confused, so I restated my words in order: "Jitter is when packets are received out of order."

A router that is connected to multiple computers, phones, appliances, and dozens of light bulbs usually has no trouble routing data packets to and from the correct device. But these data packets are often received out of order; jitter. Jitter is unimportant for email, web surfing, etc., but it is of great importance for real-time applications such as video streaming and voice communications. It matters very little how fast your internet connection is if packets arrive out of order. The acceptable jitter for video streaming is below 0.025 seconds (one-fourth of the time it takes to blink your eyes).

To minimize problems with jitter, your router needs to have an adequate jitter buffer. This means enough memory where all the out-of-order data packets can be stored for a few fractions of a second until they all arrive and can be sorted into the correct order, then routed out to the correct device on your network. The router also needs to also have enough processor speed to be able to do this sorting in milliseconds and keep doing it thousands of times per second, tens of thousands of times per minute. Better routers have built-in Quality of Service (QoS) programs a network technician could configure to prioritize real-time traffic to ensure critical packets get bandwidth preference.

Hiring a professional to configure QoS is something most internet users do not need to do. Simply installing the appropriate up-to-date router with adequate processor power and memory is often enough. Older or inexpensive network hardware is less able to cope with jitter primarily because it often lacks the capacity and advanced features needed to efficiently manage network traffic and maintain stable packet delivery. In the case of the aforementioned old Linksys WRT54G router, it was designed before smart TVs or Zoom video calls were even invented.

Finally, there are many more potential causes of jitter than the one mentioned here; these include Wi-Fi interference, substandard cabling, transient network congestion, etc. All of these causes are inherent to the internet. So the solution to jitter is to minimize the effects as much as possible by minimizing as many causes as possible, including by using up-to-date routers and other network hardware... while realizing that jitter is something that will always occur to some degree, intermittently.

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Charles Miller is a freelance computer consultant with decades of IT experience and a Texan with a lifetime love for Mexico. The opinions expressed are his own. He may be contacted at 415-101-8528 or email FAQ8 (at) SMAguru.com.

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