Quality of service (QoS) configurations give special treatment to certain traffic at the expense of others. This helps make your network performance more deterministic and predictable for this traffic. Using QoS in the network addresses the following problems:
Lack of bandwidth for important applications
Delay of sensitive data, such as voice and video
Jitter (variable delay)
Packet loss due to data being dropped at a congested interface
In a network with several hops, the available bandwidth is only as much as the smallest link. When multiple applications and multiple flows use the same links, the available bandwidth per application is even smaller—it equals the smallest link bandwidth divided by the number of flows. ...