98
98
As with all IEEE
802.11
working group standards, the goal is to provide a standard
way of implementing QoS features so that components from different companies are
interoperable. The D-Link DWL-2210AP provides QoS based on the
Wireless Multimedia
Enhancement
(
WME
) specification, which is an implementation of a subset of
802.11e
features.
QoS Queues and Parameters to Coordinate Traffic Flow
Configuring QoS options on the D-Link DWL-2210AP 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
transmission delay for VoIP, multimedia, and mission critical applications, and rely on
best-effort parameters for traditional IP data.
For example, time-sensitive multimedia and VoIP are given effectively higher priority
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 D-Link DWL-2210AP implements QoS with a custom extension to the traffic control
mechanism in the Linux kernel. Our 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.
QoS Queues and Type of Service (ToS) on Packets
QoS on the D-Link DWL-2210AP leverages existing 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 performance for that type of data.
The access point examines the ToS field in the headers of all packets that pass through
the AP. Based on the value in a packet’s ToS field, the AP prioritizes the packet for
transmission by assigning it to one of the queues. This process occurs automatically,
regardless of whether you deliberately configure QoS or not.
Configuring Queues for Qualty of Service (QoS)
Summary of Contents for AirPremier DWL-2210AP
Page 193: ...193 ...
