Psion Teklogix 9160 G2, User Manual, Page: 212 / 436

Chapter 19: Quality Of Service (QoS)
QoS Queues And Parameters To Coordinate Traffic Flow
188 Psion Teklogix 9160 G2 Wireless Gateway User Manual
The 9160 G2 Wireless Gateway provides QoS based on the Wireless Multimedia ( WMM )
specification and Wireless Multimedia (WMM) standards, which are implementations of a
subset of 802.11e features.
Both access points and wireless clients (laptops, consumer electronics products) can be
WMM-enabled.
19.1.3 QoS Queues And Parameters To Coordinate Traffic Flow
Configuring QoS options on the 9160 G2 Wireless Gateway consists of setting parameters
on existing queues for different types of wireless traffic. You can configure different
minimum and maximum wait times for the transmission of packets in each queue based on
the requirements of the media being sent. Queues automatically provide minimum transmis-
sion delay for Voice, Video, multimedia, and mission critical applications, and rely on best-
effort parameters for traditional IP data.
For example, time-sensitive Voice, Video, and multimedia are given effectively higher prior-
ity for transmission (lower wait times for channel access), while other applications and
traditional IP data which are less time-sensitive but often more data-intensive are expected
to tolerate longer wait times.
The 9160 G2 Wireless Gateway implements QoS based on the IEEE Wireless Multimedia
(WMM) standard. A Linux-based queuing class is used to tag packets and establish multiple
queues. The queues provided offer built-in prioritization and routing based on the type of
data being transmitted.
The Administration UI provides a way for you to configure parameters on the queues.
19.1.3.1 QoS Queues And Type Of Service (ToS) On Packets
QoS on the 9160 G2 Wireless Gateway leverages WMM information in the IP packet
header related to Type of Service ( ToS ). Every IP packet sent over the network includes a
ToS field in the header that indicates how the data should be prioritized and transmitted over
the network. The ToS field consists of a 3 to 7 bit value with each bit representing a different
aspect or degree of priority for this data as well as other meta-information (low delay, high
throughput, high reliability, low cost, and so on).
For example, the ToS for FTP data packets is likely to be set for maximum throughput since
the critical consideration for FTP is the ability to transmit relatively large amounts of data in
one go. Interactive feedback is a nice-to-have in this situation but certainly less critical. VoIP
data packets are set for minimum delay because that is a critical factor in quality and perfor-
mance for that type of data.