Which of the following are examples of metrics for QoS?

Quality of Service (QoS) is measured using specific performance metrics that quantify the network's performance from an application's perspective. The three most fundamental and universally recognized metrics are: Delay (Latency): The time it takes for a packet to travel from its source to its destination. Jitter: The variation in the end-to-end delay of packets in the same flow. Packet Loss: The percentage of packets that are dropped by the network and fail to reach their destination. These three metrics directly impact the user-perceived quality of real-time and data applications.

A. Signal degradation and attenuation are physical layer (Layer 1) phenomena, not direct QoS service metrics used for packet forwarding.
B. FIFO and WRED are queuing mechanisms used to implement QoS policies, not metrics used to measure network performance.
D. SNR (Signal-to-Noise Ratio) is a physical layer metric, and queue depth is an operational parameter, not a primary end-to-end QoS metric.
E. Attenuation and dispersion are physical layer (Layer 1) signal impairments, not packet-level QoS metrics.

1. Nokia Quality of Service Course (4A0-107) Student Guide, Module 1: Introduction to QoS. This module introduces the fundamental network performance characteristics that QoS aims to manage, explicitly identifying delay, jitter, and packet loss as the primary metrics.

2. Nokia 7750 SR OS 21.10.R1 Quality of Service Guide, Part 1, Chapter: "QoS Overview". The introductory section states, "The goal of QoS is to provide preferential forwarding for certain packets over other packets... Preferential forwarding is based on the QoS requirement of the application. For example, VoIP and video applications are sensitive to packet delay and delay variation (jitter), and packet loss."

3. Kurose, J. F., & Ross, K. W. (2021). Computer Networking: A Top-Down Approach (8th ed.). Chapter 7, Section 7.1.1, "Properties of Video and Voice-over-IP." This section details the network requirements for real-time applications, focusing on their sensitivity to packet delay, jitter, and loss, establishing these as critical QoS metrics.