Allied Telesis AT-8000GS User's Guide download pdf (Page 155)

Configuring Services

Page 155

Section 13. Configuring Services

This section describes Quality of Service related configurations. QoS supports activating one of the following Trust

settings:

• VLAN Priority Tag

• DiffServ Code Point

• None

Only packets that have a Forward action are assigned to the output queue, based on the specified classification.

By properly configuring the output queues, the following basic mode services can be set:

• Minimum Delay — The queue is assigned to a strict priority policy, and traffic is assigned to the highest

priority queue.

• Best Effort — Traffic is assigned to the lowest priority queue

• Bandwidth Assignments — Bandwidths are assigned by configuring the WRR scheduling scheme.

After packets are assigned to a specific egress queue, Class of Service (CoS) services can be assigned to the

queue. Egress queues are configured with a scheduling scheme by one of the following methods:

• Strict Priority — Ensures that time-sensitive applications are always forwarded. Strict Priority (SP) allows

the prioritization of mission-critical, time-sensitive traffic over less time-sensitive applications. For example,

under SP, voice over IP (VoIP) traffic can be prioritized so that it is forwarded before FTP or e-mail (SMTP)

traffic.

• Weighted Round Robin — Ensures that a single application does not dominate the device forwarding

capacity. Weighted Round Robin (WRR) forwards entire queues in a round robin order. All queues can

participate in WRR, except SP queues. SP queues are serviced before WRR queues. If the traffic flow is

minimal, and SP queues do not occupy the whole bandwidth allocated to a port, the WRR queues can share

the bandwidth with the SP queues. This ensures that the remaining bandwidth is distributed according to the

weight ratio. If WRR is selected, the following weights are assigned to the queues: 1, 2, 4, 8.

This section contains the following topics:

• Enabling Class of Service (CoS)

• Configuring CoS Queueing and Scheduling

• Mapping CoS Values to Queues

• Mapping DSCP Values to Queues

• Configuring QoS Bandwidth

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Allied Telesis AT-8000GS User's Guide Page 155