Old rules, new networks: rethinking QoS for modern UC

Hybrid meeting with a group of people in a meeting room speaking with other people via videoconference – TeleDynamics blog

UC is an area of telecom that has seen massive, rapid change in recent years. However, even given radical technological shifts, some principles remain the same. The need for quality of service (QoS) is one of them.

In this article, we take a fresh look at QoS from the vantage point of today’s UC, taking into account not only advances in QoS itself, but also in the underlying network infrastructure that serves it.

The evolution of UC

Today's UC is unrecognizable compared to what it looked like over a decade ago, with changes affecting every aspect of its operation. It has been reinvented over several iterations, from centralized on-prem systems with local connectivity to cloud-centric UCaaS deployments serving distributed networks and workforces. Innovations, including the introduction of soft clients for PCs and mobile devices, virtual contact centers, and integrations with a whole series of third-party business applications have gone a long way towards advancing UC as a service.

UC's operation has also been enriched with video, text, file sharing, and a wide variety of advanced AI features. The underlying network infrastructure that supports it has also played a significant role as an enabler, with connectivity and transmission options arriving that include SD-WAN, MPLS, wireless, 5G, VPNs, and satellite communication services.

These and many more innovations are part of today’s UC ecosystem, and this exciting development path is only expected to continue. However, even in such a dynamic development, certain things remain unchanged.

Unchanging QoS principles

No matter how advanced the technology or innovative the implementation, some things cannot be changed. The laws of physics are one of them. Signal speed and link capacities are fundamental limits enforced by the physical nature of transmission media. These limitations directly affect the main phenomena that can be detrimental to the operation of UC: jitter, latency, and packet loss.

Because these factors are always present, any network design strategy must include a robust QoS component. One of the worst mistakes that a network designer can make is to say: “Well, we have plenty of bandwidth, so we don’t need to deploy any QoS mechanisms.”

It doesn’t matter how much bandwidth is available; network conditions are dynamic and cannot be fully predicted. Congestion issues can result in signals and capacities unexpectedly hitting physical limits, resulting in degradation in service, hampered communication, and dissatisfied employees and customers. Not to mention a degradation in the service your enterprise delivers, which can translate into financial losses.

It cannot be overstated that QoS must be deployed appropriately regardless of the available bandwidth and how advanced the UC deployment and underlying network infrastructure are!

QoS for UC: old concept, new angle

QoS is as old as VoIP and originally became more prevalent with the proliferation of packetized voice. Since then, QoS hasn’t changed in essence. It involves identifying real-time flows, marking them, and then giving them the proper treatment. What has changed is the scope of implementation.

Underlying network

Instead of a single, private LAN and WAN on which endpoints operate, UC media now crosses multiple networks, including Wi-Fi, SD-WAN, mobile, and MPLS overlays, public internet infrastructure, and cloud edges, all of which are outside the enterprise’s control.

This means that any classifications and markings applied to UC media packets may not be honored by these third-party networks and may even be modified or removed. Designers must define clear trust boundaries: where markings are accepted, where they must be restored at the first hop you control, and where to build small QoS trust domains with enforceable protections, so quality holds even when much of the path is best effort.

A single UC communication may traverse many networks, each of which may employ network features that can inadvertently modify or remove QoS markings. Employed QoS policies should be designed to survive these features, including encryption, NAT, SD-WAN and others.

UC multiple channels

The other major shift with QoS design for UC is that we’re not just applying it to voice packets. Modern UC sessions carry multiple concurrent streams, each with QoS requirements and thresholds. These include stereo and spatial audio, HD and 4K video, screen and media sharing, text chat, control signaling, and AI-enabled features. Each of these types of communications requires different QoS targets and thresholds:

Audio is low bandwidth, but highly sensitive to latency and jitter.
Interactive video needs sustained throughput, but tolerates some packet loss.
Screen and media sharing is bursty and is usually less delay-critical.
Signaling is very low in volume, but must be given priority.
AI features may require multiple media streams with some level of synchronization among them.
Text messages and file transfer require nothing more than best effort.

A practical approach is to collapse all these channels into three or four traffic classes rather than creating a class for each feature. Then, per-class thresholds and control should be applied so a surge in video or media sharing won’t starve voice or signaling. This simplifies QoS application while maintaining enough QoS diversity to appropriately serve all types of communication.

Implementing QoS on modern networks

Much of the QoS design approach requires network architects to be aware of the characteristics of modern UC and to consider them when designing networks that will serve mission-critical UC systems and services. Because network infrastructure typically outlives any single UC platform deployment, QoS policies should transcend UC upgrades and be vendor agnostic. Properly implemented, the QoS you deploy today will carry the next wave of UC features while preserving the call and meeting quality your users expect.

Conclusion

While UC technologies will continue to advance, the basic factors that influence quality remain unchanged. Latency, jitter, and packet loss will continue to shape the user experience and require deliberate management. By designing QoS to align with today’s network realities, organizations can ensure consistent call and meeting quality as UC capabilities evolve.