What is QoS? A Look at the Factors Behind Call and Video Quality

If you've read a technology white paper, vendor sales page, or similar product-focused document in the past two decades, you've probably encountered the term "quality of service" (QoS) many times over, even if you don't know the exact QoS definition. Moreover, you've probably seen it at a more consistent rate over the past several years as a growing number of businesses come to embrace the technologies it encompasses and the benefits it offers.

Naturally, you probably have some questions. How do you achieve QoS? When do you need to be concerned about it? And, what is QoS?

The answers to these questions are as follows: It depends, it depends, and it's (sort of) complicated. That's especially true when you throw in terminology such as "quality of experience" (QoE), which serves a different purpose but sounds similar enough to create confusion. So, what exactly is QoS?

What is QoS?

A streaming video buffers for an inordinate amount of time. A VoIP call comes through garbled. A video conference makes the person on the screen look like something out of a Dalí painting. These are all examples of what happens when a system fails to achieve QoS — and, in turn, a list of reasons you need QoS in the first place.

In this sense, you can say QoS is a grouping of technologies, strategies, and quality metrics that improve the transmission of packets from one point to another. Generally speaking, QoS measures are concerned with factors "under the hood" of the communications technologies you rely on. While QoS is all about providing good service, in other words, it achieves these means by monitoring and altering technical aspects users rarely consider. Total network bandwidth will usually be of serious concern to a QoS solution, as will factors such as packet sequencing.

Naturally, QoS metrics and tools came about as responses to growing technological demand. Many of the tools businesses and private users leverage daily are performance- and speed-sensitive. A video conference needs a precise sequence of packets to faithfully render your colleague's smiling face and helpful words. A VoIP call needs similar accuracy and speed to ensure the voice data transmitted to your receiver comes in the right order. The same several countless other technologies that require more speed and precision than your average website to download all need QoS.

To this end, mounting public expectations make QoS even more important than ever. Today's users have come to accept network communication tools, and with that acceptance comes a baseline expectation of quality. In turn, this is why QoS terms are in so many vendor contracts and why solutions providers and client companies alike go to great pains to monitor the factors that might affect service quality.

How do you achieve QoS? When do you need to be concerned about it? And what is QoS?

Why Prioritization Matters

Then there's the idea of prioritization. At the risk of sounding insensitive, the modern network is still fairly dumb. For example, it generally can't tell whether the data it's transmitting comes from a VoIP call or a downloaded website. Combined with those ever-growing user expectations, you have a nasty situation waiting to happen. When your intern's fantasy football podcast loads with better quality than your important video conference because it "got there first" in terms of network resource usage, something needs to change.

Thus, the answer to the question, "What is QoS?" can be the prioritization of data on the network. A tool that helps put data in the right order can be a QoS technology.

Take SD-WAN for UCaaS, a technology class that applies the principles of software-defined networking (SDN) to unified communications tools. With this technology, business networks can give preferential treatment to communication data, then shape and sort the resulting traffic over one or more data connections to ensure top-shelf quality without affecting the way other people work. For example, your important training conference might be routed in tandem over your employer's primary data connection and its backup 4G LTE line without you noticing anything but an extreme uptick in audiovisual fidelity.

This example shines because it illustrates the positive benefits relatively simple QoS measures can have. A business forced to use a larger bandwidth package to support video conferencing could drop to a lower package, thus increasing quality and saving money in a single move. By the same token, a business may cultivate improved service quality by linking its sites with an MPLS private circuit or employing a hybrid network of MPLS and business-broadband connections interlinked with SDN tools.

QoS and QoE

It's also important to note QoS and QoE are not the same. At issue is the idea of subjectivity. Where QoS covers specific, measurable figures — the number of dropped packets or the amount of available bandwidth — QoE attempts to measure the user's overall experience. In car terms, it's the difference between saying, "This car has heated seats, a satellite radio, and a backup camera," and asking everyone who visits the lot what they thought after test-driving the car.

You could say good QoS makes real QoE possible. When you provide an elevated QoS and your users are happier for it, you're working toward good QoE. If your QoS leaves something to be desired, on the other hand, your QoE will suffer. Understanding the difference is another key step in understanding what QoS is — a crucial lesson, considering just how big a role QoS tools play in improving the solutions professionals everywhere use to communicate.

Do you crave better bandwidth efficiency? Contact Vonage Business.

Evan Wade
Evan Wade Contributor



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