Draytek VigorAP 710 - Airtime Fairness

VigorAP 710 User’s Guide
87
CWMin/CWMax
CWMin means contention Window-Min and CWMax means
contention Window-Max. Please specify the value ranging from
1 to 15. Be aware that CWMax value must be greater than
CWMin or equals to CWMin value. Both values will influence
the time delay for WMM accessing categories. The difference
between AC_VI and AC_VO categories must be smaller;
however, the difference between AC_BE and AC_BK categories
must be greater.
Txop
It means transmission opportunity. For WMM categories of
AC_VI and AC_VO that need higher priorities in data
transmission, please set greater value for them to get highest
transmission opportunity. Specify the value ranging from 0 to
65535.
ACM
It is an abbreviation of Admission control Mandatory. It can
restrict stations from using specific category class if it is
checked.
Note: Vigor2120 provides standard WMM configuration in the
web page. If you want to modify the parameters, please refer to
the Wi-Fi WMM standard specification.
AckPolicy
“Uncheck” (default value) the box means the AP router will
answer the response request while transmitting WMM packets
through wireless connection. It can assure that the peer must
receive the WMM packets.
“Check” the box means the AP router will not answer any
response request for the transmitting packets. It will have better
performance with lower reliability.
After finishing this web page configuration, please click OK to save the settings.
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Airtime fairness is essential in wireless networks that must support critical enterprise
applications.
Most of the applications are either symmetric or require more downlink than uplink capacity;
telephony and email send the same amount of data in each direction, while video streaming
and web surfing involve more traffic sent from access points to clients than the other way
around. This is essential for ensuring predictable performance and quality-of-service, as well
as allowing 802.11n and legacy clients to coexist on the same network. Without airtime
fairness, offices using mixed mode networks risk having legacy clients slow down the entire
network or letting the fastest client(s) crowd out other users.
With airtime fairness, every client at a given quality-of-service level has equal access to the
network's airtime.
The wireless channel can be accessed by only one wireless station at the same time.
The principle behind the IEEE802.11 channel access mechanisms is that each station has
equal probability to access the channel. When wireless stations have similar data rate, this
principle leads to a fair result. In this case, stations get similar channel access time which is
called airtime.