Netgear GS752TS GS7xxTS-TPS Software Admin Manual - Page 177

Configuring Quality of Service, Class of Service

Page 177 highlights

5. Configuring Quality of Service 5 Use the features in the QoS tab to configure Quality of Service (QoS) settings on the switch. The QoS tab contains links to the following features: • Class of Service on page 177 • Differentiated Services on page 184 In a typical switch, each physical port consists of one or more queues for transmitting packets on the attached network. Multiple queues per port are often provided to give preference to certain packets over others based on user-defined criteria. When a packet is queued for transmission in a port, the rate at which it is serviced depends on how the queue is configured and possibly the amount of traffic present in the other queues of the port. If a delay is necessary, packets get held in the queue until the scheduler authorizes the queue for transmission. As queues become full, packets have no place to be held for transmission and get dropped by the switch. QoS is a means of providing consistent, predictable data delivery by distinguishing between packets that have strict timing requirements from those that are more tolerant of delay. Packets with strict timing requirements are given "special treatment" in a QoS-capable network. With this in mind, all elements of the network must be QoS-capable. The presence of at least one node which is not QoS-capable creates a deficiency in the network path and the performance of the entire packet flow is compromised. Class of Service The Class of Service (CoS) queueing feature lets you directly configure certain aspects of switch queueing. This provides the desired QoS behavior for different types of network traffic when the complexities of DiffServ are not required. The priority of a packet arriving at an interface can be used to steer the packet to the appropriate outbound CoS queue through a mapping table. CoS queue characteristics that affect queue mapping, such as minimum guaranteed bandwidth, or transmission rate shaping are user-configurable at the queue (or port) level. Four queues per port are supported. 177

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177
5
5.
Configuring Quality
of Service
Use the features in the QoS tab to configure Quality of Service (QoS) settings on the switch. The
QoS tab contains links to the following features:
Class of Service
on page
177
Differentiated Services
on page
184
In a typical switch, each physical port consists of one or more queues for transmitting
packets on the attached network. Multiple queues per port are often provided to give
preference to certain packets over others based on user-defined criteria. When a packet is
queued for transmission in a port, the rate at which it is serviced depends on how the queue
is configured and possibly the amount of traffic present in the other queues of the port. If a
delay is necessary, packets get held in the queue until the scheduler authorizes the queue
for transmission. As queues become full, packets have no place to be held for transmission
and get dropped by the switch.
QoS is a means of providing consistent, predictable data delivery by distinguishing between
packets that have strict timing requirements from those that are more tolerant of delay.
Packets with strict timing requirements are given “special treatment” in a QoS-capable
network. With this in mind, all elements of the network must be QoS-capable. The presence
of at least one node which is not QoS-capable creates a deficiency in the network path and
the performance of the entire packet flow is compromised.
Class of Service
The Class of Service (CoS) queueing feature lets you directly configure certain aspects of
switch queueing. This provides the desired QoS behavior for different types of network traffic
when the complexities of DiffServ are not required. The priority of a packet arriving at an
interface can be used to steer the packet to the appropriate outbound CoS queue through a
mapping table. CoS queue characteristics that affect queue mapping, such as minimum
guaranteed bandwidth, or transmission rate shaping are user-configurable at the queue (or
port) level.
Four queues per port are supported.