Avaya BSGx4e CLI Guía de usuario descargar pdf (Pagina 144)

Switch commands 3 Configuration commands

144 NN47928-107

qos

The LAN switch in the BSGX4e provides a layer 2 Quality of Service (QoS)

feature. This feature enables prioritization of network traffic, which is

essential for the protection of time-sensitive traffic such as VoIP phone

calls.

Because it has multiple LAN ports to send traffic to the WAN and only one

WAN interface to send that traffic, the BSGX4e must prioritize the traffic it

routes. Layer 2 QoS is provided to guarantee that higher priority traffic is

routed while lower priority traffic can be delayed or discarded. Layer 2 QoS

is most effective for traffic switched from the LAN to the IP host to be routed

to the WAN.

For a full QoS solution to manage LAN to WAN traffic, configuration of layer

3 QoS is also recommended. For information about the layer 3 QoS

implementation, see QoS (GoS) commands on page 89

Layer 2 QoS provides four queues to classify and prioritize network traffic:

LOWESTQ, LOWQ, HIGHQ and HIGHESTQ. LOWESTQ is the lowest

priority queue; HIGHESTQ is the highest priority queue. The four queues

are assigned weights (8:4:2:1) that determine the time and number of

packets serviced from the queue. (The queue weighting cannot be changed.)

Two scheduling methods are available; the default method is WFQ:

z Weighted Fair Queuing (WFQ)

All queues are serviced depending on the weight assigned to the queue.

No starvation occurs, that is, even the lowest priority queue receives

service periodically.

z Fixed

All priority packets are serviced from a queue until that queue is empty,

and then the next lower-priority queue is serviced, and so on. Starvation

can occur, that is, the traffic load for a higher-priority queue can prevent

lower-priority queues from being serviced.

Packets are classified and then assigned to one of the four priority queues.

Layer 2 QoS can classify traffic using any one of the following criteria:

z Port number (the default classification has all ports mapped to

LOWESTQ)

z IEEE 802.1p tag

z DiffServ/ToS tag

The table below lists the default priority queues depending on the criteria

used for classification.

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Avaya BSGx4e CLI Guía de usuario Pagina 144