Billion BiPAC 6200WZL R2 User Manual page 129

For Mail Sending
Here we guarantee 30% of the traffic for Mail application.
thus, 20% of LAN to WAN (upsteam) traffic is reserved for other uses and those applications'
bandwidths are guaranteed.
For downstream traffic bandwidth, just the direction changes and the configuration is similar.
That's just a simple example for QoS application, for more please refer to Billion FAE.
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