QoS stands for Quality of Service and is a mechanism that allows network devices to prioritize and differentiate traffic based on certain criteria, such as application type, source, destination, etc3. QoS involves identifying specific traffic for special treatment and applying policies and actions to improve its performance or meet certain service level agreements (SLAs)3. QoS can help network devices to manage congestion, delay, jitter, packet loss, bandwidth allocation, etc., for different types of traffic3. QoS can be implemented at various layers of the network stack and across different network domains. References: 3 https://www.cisco.com/c/en/us/td/docs/ios-xml/ios/qos/configuration/15-mt/qos-15-mt-book/qos-overview.html