Quality of Service (QoS) is a set of standards and measures that define the performance and reliability levels of a telecommunications network, system, or service. It focuses on ensuring a consistent and acceptable level of service to meet users' requirements and expectations.

Key aspects and components of Quality of Service include:

Latency: The time it takes for data to travel from the sender to the receiver, affecting the responsiveness of real-time applications like voice and video.

Bandwidth: The maximum data transfer rate or capacity of the network, impacting the amount of data that can be transmitted within a given time.

Jitter: The variation in latency or delay between data packets, which can affect the quality of real-time communications.

Packet Loss: The percentage of data packets lost during transmission, which can degrade the quality of communication and user experience.

QoS mechanisms prioritize and manage network traffic to meet these parameters, ensuring a consistent level of service and a satisfactory user experience. It is especially crucial for real-time applications, such as VoIP (Voice over Internet Protocol) and video conferencing.