The Value of QoS on Computer Networks

RJ45 or Ethernet cable
Mizanur Rahman / Moment / Getty Images

QoS (Quality of Service) refers to a broad set of networking technologies and techniques designed to guarantee predictable levels of network performance. Elements of network performance within the scope of QoS include availability (uptime), bandwidth (throughput), latency (delay), and error rate (packet loss).

Building a Network With QoS

QoS involves prioritization of network traffic. QoS can be targeted at a network interface, toward a given server or router, or at specific applications. A network monitoring system must typically be deployed as part of a QoS solution to ensure that networks are performing at the desired level.

QoS is especially important for Internet applications such as video-on-demand, voice over IP (VoIP) systems, and other consumer services where high-performance and high-quality streaming is involved.

Traffic Shaping and Traffic Policing

Some people use the terms traffic shaping and QoS interchangeably as shaping is one of the most common techniques used in QoS. Traffic shaping trades off adding delays to one source stream of traffic to improve the latency of another source.

Traffic policing in QoS involves monitoring connection traffic and comparing the activity levels against pre-defined thresholds (policies). Traffic policing typically results in packet loss on the receiving side as messages get dropped when the sender exceeds policy limits.

QoS on Home Networks

Many home broadband routers implement QoS in some form. Some home routers implement automated QoS features (often called intelligent QoS) that require minimal setup effort but somewhat less capability than manually-configured QoS options.

Automatic QoS detects different kinds of network traffic (video, audio, gaming) according to its data types and makes dynamic routing decisions based on predefined priorities.

Manual QoS enables a router administrator to configure their own priorities based on traffic type but also on other network parameters (such as individual client IP addresses). Wired (Ethernet) and wireless (Wi-Fi) QoS require separate setup. For wireless QoS, many routers implement a standard technology called WMM (WI-Fi Multimedia) that provides the administrator with four categories of traffic that can be prioritized against each other — Video, Voice, Best Effort, and Background.

Issues With QoS

Automatic QoS may have undesirable side effects (excessively and unnecessarily impacting the performance of basic priority traffic by over-prioritizing traffic at a higher tier), It can be technically challenging for untrained administrators to implement and tune.

Some core networking technologies like Ethernet were not designed to support prioritized traffic or guaranteed performance levels, making it much more difficult to implement QoS solutions across the Internet.

Whereas a household can maintain full control over QoS on their home network, they are dependent on their Internet provider for QoS choices made at the global level. Consumers can logically have concerns with providers having the high degree of control over their traffic that QoS offers.