Alvarion BreezeACCESS VL System Manual page 213

Show TCP Port Ranges: Select this option to view the current TCP
RTP/RTCP Prioritization option and the list of TCP Port Ranges.
4.2.6.6.3.4 Low Priority Traffic Minimum Percent
This feature ensures that a certain amount of low priority packets, specified by
the Low Priority Traffic Minimum Percent (LPTMP) parameter, is transmitted even
at the expense of high priority traffic.
The mechanism guarantees a low priority traffic with a rate of LPTMP * RT /100,
where RT symbolizes the allowed traffic rate. The high priority traffic will thus not
be able to exceed (100-LPTMP) * RT/100. If the system receives high priority
traffic at a rate higher than this figure, some high priority packets will be
discarded.
The range is between 0 and 100 (%).
The default value is 0 (%).
4.2.6.6.3.5 Wireless Link Prioritization Parameters (AU)
To better support delay-sensitive and other high-priority traffic, a set of Wireless
Link Prioritization parameters enables configuring parameters that affect the
processes of gaining access to the wireless media and of transmitting high/low
priority packets.
The Wireless Link Prioritization feature is a licensed feature and is available only
in units with the suitable Feature License.
The time interval between two consecutive transmissions of frames is called Inter-
Frame Spacing (IFS). This is the time during which the unit determines whether
the medium is idle using the carrier sense mechanism. The IFS depends on the
type of the next frame to be transmitted, as follows:
SIFS (Short Inter-Frame Spacing) is used for certain frames that should be
transmitted immediately, such as ACK and CTS frames. The value of SIFS is
16 microseconds.
DIFS (Distributed coordination function Inter-Frame Spacing) is typically
used for other frame types when the medium is free. If the unit decides that
the medium is not free, it will defer transmission by DIFS plus a number of
time slots as determined by the Contention Window back-off algorithm after
reaching a decision that the medium has become free. DIFS equal SIFS plus
AIFS, where AIFS is a configurable number of time slots.
Under regular conditions, AIFS is configured to two time slots. To support
prioritization in the wireless link, we can configure a higher AIFS for low priority
traffic (AIFS of two time slots will always be used for high priority traffic as well as
AU's transmissions of broadcasts/multicasts and beacons). This will give
Operation and Administration
Menus and Parameters
187