Does QoS protect against excessive bandwidth usage on a link?

The assertion that Quality of Service (QoS) protects against excessive bandwidth usage on a link is inaccurate. QoS is primarily a set of techniques and mechanisms designed to prioritize different types of network traffic to ensure a consistent level of performance, especially for time-sensitive applications like audio and video streaming. While QoS can help manage and allocate available bandwidth by prioritizing certain data packets over others, it does not inherently limit or prevent excessive bandwidth usage itself on a network link.

Bandwidth management involves controlling the amount of bandwidth that certain applications or users can consume, which can sometimes be addressed with limits, shaping, or throttling techniques separate from QoS mechanisms. Thus, the understanding of QoS's role clarifies that while it can enhance the performance of critical applications amid competing traffic, it won't inherently block or reduce bandwidth usage itself.