Draytek Vigor2920 Series User Manual page 273

Available settings are explained as follows:
Item
Enable the QoS Control
WAN Inbound
Bandwidth
WAN Outbound
Bandwidth
Reserved Bandwidth
Ratio
Enable UDP Bandwidth
Control
Outbound TCP ACK
Description
The factory default for this setting is checked.
Please also define which traffic the QoS Control settings will
apply to.
IN- apply to incoming traffic only.
OUT- apply to outgoing traffic only.
BOTH- apply to both incoming and outgoing traffic.
Check this box and click OK, then click Setup link again. You
will see the Online Statistics link appearing on this page.
It allows you to set the connecting rate of data input for WAN.
For example, if your ADSL supports 1M of downstream and
256K upstream, please set 1000kbps for this box. The default
value is 10000kbps.
It allows you to set the connecting rate of data output for
WAN. For example, if your ADSL supports 1M of
downstream and 256K upstream, please set 256kbps for this
box. The default value is 10000kbps.
Note: The rate of outbound/inbound must be smaller than
the real bandwidth to ensure correct calculation of QoS. It
is suggested to set the bandwidth value for
inbound/outbound as 80% - 85% of physical network
speed provided by ISP to maximize the QoS performance.
It is reserved for the group index in the form of ratio of
reserved bandwidth to upstream speed and reserved
bandwidth to downstream speed.
Check this and set the limited bandwidth ratio on the right
field. This is a protection of TCP application traffic since UDP
application traffic such as streaming video will exhaust lots of
bandwidth.
The difference in bandwidth between download and upload are
great in ADSL2+ environment. For the download speed might
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Vigor2920 Series User's Guide