[1] It is used by network administrators, to reduce congestion, latency and packet loss.
In order to use these tools effectively, it is necessary to measure the network traffic to determine the causes of network congestion and attack those problems specifically.
Network traffic control is an important subject in datacenters as it is necessary for efficient use of datacenter network bandwidth and for maintaining service level agreements.
[1] Traffic shaping is the retiming (delaying) of packets (or frames) until they meet specified bandwidth and or burstiness limits.
Traffic policing is the dropping (discarding) or reduction in priority (demoting) of packets (or frames) that exceed some specified bandwidth and or burstiness limit.