BGP (Border Gateway Protocol) does not directly measure the quality of service (QoS) of a network. Instead, it primarily focuses on the path selection criteria to choose the best available route among multiple paths towards a destination network. The path selection criteria include factors such as AS path length, network policies, local preference, MED (Multi-Exit Discriminator), and others.
However, BGP can indirectly impact QoS by influencing the path taken for network traffic. For example, BGP can select a path with lower latency or better bandwidth, which can result in better QoS for end-users. Additionally, BGP can be used in conjunction with other QoS mechanisms such as traffic engineering and quality of service (QoS) policies to improve QoS in a network. This can include techniques such as prioritizing traffic for mission-critical applications, reducing network congestion, and ensuring sufficient bandwidth for specific types of traffic.
