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Quality of Service
Defining Queues
STEP 1
STEP 2
Cisco Small Business SG200 Series 8-port Smart Switches Administration Guide
Queue Configuration Recommendations
It is recommended that higher numbered queues be configured with higher
priority, weight, and minimum-bandwidth settings.
The following are recommended scenarios for strict priority (SP) and WRR on
queues 1–4:
•
All four queues in SP mode (Q4 > Q3 > Q2 > Q1). Q4 is allocated bandwidth
as long as there are packets to serve in Q4. Then Q3 is served, followed by
Q2 and Q1 in order.
•
All 4-queues in WRR mode (Q4:Q3:Q2:Q1 = A:B:C:D). In this mode, each
queue is allocated its minimum bandwidth according to the weights
configured.
•
One queue in SP mode and three queues in WRR mode (Q4 > Q3/Q2/Q1;
Q3:Q2:Q1 = A:B:C). In this scenario, it is recommended that Q4 be
configured in SP mode and Q3, Q2, and Q1 in WRR mode.
•
Two queues in SP mode and two queues in WRR mode (q4 > q3 > q2/q1;
q2:q1 = A:B): In this scenario, it is recommended that Q4 and Q3 be
configured in strict mode with Q2 and Q1 in WRR mode.
These scenarios reflect that when there are more ingress ports with traffic
destined to different queues on egress ports, a system might encounter a Head of
Line Blocking (HOL) condition. HOL might result in higher numbered queues
getting more bandwidth, although higher numbered queues are configured with a
lesser minimum bandwidth and weight. It is always recommended that higher
numbered queues with higher weight configured in SP mode, so that even in an
HOL condition, the desired egress segregation would be achieved among queues.
Configuring Queues
To configure QoS properties:
Click Quality of Service > Queue in the navigation window.
Select port or LAG to configure.
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