Automatic Channel Select; Quality Of Service; Different Dimensions Of Qos; Packet Filtering - Symbol WS5000 series Reference Manual

1.3.7 Automatic Channel Select

The Automatic Channel Selection (ACS) feature enables the switch to determine the best radio frequency or
channel for access port performance. The switch determines the best channel for each access port through a
set of algorithms that analyze the channels permitted by country regulations and the relative signal strength
of each access port in the wireless coverage area.
Using ACS optimizes channel selection which is helpful in areas where coverage is dynamic because either
the site itself changes or coverage needs change. As conditions change, ACS is used to adapt and obtain the
best coverage.

1.3.8 Quality of Service

QoS is used to give a user or an application relative precedence or priority over another. QoS applies in the
case of congestion that may occur from excessive traffic or different data rates and link speeds—10Mbps
Ethernet, 100 Mbps Ethernet, 11Mbps Wireless, and so on—that exist in the same network.
If there is enough bandwidth for all users and applications (unlikely because excessive bandwidth comes at a
very high cost), then applying QoS has very little value. When total bandwidth is shared by different users and
applications, QoS is required to provide policy enforcement for mission-critical applications and/or users that
have critical bandwidth requirements.

1.3.8.1 Different Dimensions of QoS

Different methods of QoS are applied for distinction between users and applications. The two main categories
are:
• QoS via Queuing – A network shared by different users such as in a revenue-based, shared office
building or a public hotspot is implemented with Service Level Agreements (SLA) based on how much
each group of users pay for bandwidth. In this case, one or all points of aggregation, such as the switch
and some high-end routers or policy managers, can allocate different percentages of the total
bandwidth to different groups of users through the use of queues. Bandwidth allocation can also be
further divided and applied to different applications again using Queues.
• Application QoS via Packet Marking – A network or a portion of the allocated bandwidth can be shared
by different applications, and one application—for example, voice communication—can be more
latency sensitive or more mission-critical than others. In this case, a priority is assigned to the traffic
type by adding the appropriate QoS marking or tags to network traffic to provide higher precedence
while the data is passed through points of aggregation—routers, switch(es), and gateways—and the
medium of transfer.

1.3.8.2 Packet Filtering

Packet filtering is a decision to allow or discard packets matching certain criteria defined by Classification
Groups (CG) on an output packet port. Classification groups on an output port are defined with allow decisions,
discard decisions or a combination of both. A CG defined with an allow condition is associated with a priority
number in the range of 0 – 7, seven being the highest priority.

1.3.8.3 Weighted Fair Queuing (WFQ)

Weighted Fair Queuing (WFQ) enables a mechanism on the switch that uses up to eight queues to store data—
network packets—and prioritize RF transmission to and from MUs depending on the data type. Once data is
classified as voice or data, WFQ stores the packets, assuming the network traffic demands that the data be
queued, by data type, then transmits the packets at a rate specified by the WFQ allocation percentage setting.
WS5000 Series Switch Overview 1-11