Draytek Vigor2762 series User Manual page 335

checking before executing treatments in order to ensure service-level consistency
throughout the whole QoS-enabled network.
However, each node may take different attitude toward packets with high priority marking
since it may bind with the business deal of SLA among different DS domain owners. It's not
easy to achieve deterministic and consistent high-priority QoS traffic throughout the whole
network with merely Vigor router's effort.
Vigor2762 Series User's Guide 325