Quality of Service (QoS) refers to a collection of technologies and techniques used to manage and optimize network traffic. The primary goal of QoS is to ensure the efficient and reliable transmission of data across a network by prioritizing certain types of traffic and allocating bandwidth accordingly. This is particularly important in networks where bandwidth is limited or where certain applications require guaranteed performance levels.

QoS works by reducing packet loss, which occurs when data packets traveling across a network fail to reach their destination. It also minimizes latency, which is the delay experienced in the transmission of data, and jitter, which is the variation in packet arrival times. These factors are crucial for maintaining the quality of real-time applications such as voice over IP (VoIP), video conferencing, and online gaming, where delays or interruptions can significantly impact user experience.

To achieve these objectives, QoS employs various mechanisms such as traffic shaping, which controls the flow of data to ensure a smooth and consistent transmission rate; prioritization, which assigns different levels of importance to different types of traffic; and resource reservation, which allocates specific amounts of bandwidth to critical applications. By implementing QoS, network administrators can ensure that high-priority applications receive the necessary resources to function optimally, even during periods of high network congestion.