Configuring Port Scheduler Policies - Alcatel-Lucent 7450 Quality Of Service Manual

Configuring Port Scheduler Policies

Port Scheduler Structure
Every port scheduler supports eight strict priority levels with a two pass bandwidth allocation
mechanism for each priority level. Priority levels 8 through 1 (level 8 is the highest priority)
are available for port-parent association for child queues and schedulers. Each priority level
supports a maximum rate limit parameter that limits the amount of bandwidth that may be
allocated to that level. A CIR parameter is also supported that limits the amount of bandwidth
allocated to the priority level for the child queue's offered load, within their defined CIR. An
overall maximum rate parameter defines the total bandwidth that will be allocated to all
priority levels.
Special Orphan Queue and Scheduler Behavior
When a port scheduler is present on an egress port or channel, the system ensures that all
queues and schedulers receive bandwidth from that scheduler to prevent free-running queues
which can cause the aggregate operational PIR of the port or channel to oversubscribe the
bandwidth available. When the aggregate maximum rate for the queues on a port or channel
operate above the available line rate, the forwarding ratio between the queues will be affected
Quality of Service Guide
Figure 34: Resulting Bandwidth Distribution
No Traffic
Offered Default Second
Traffic H-Qos Pass (LUB)
0 100 20
0 100 20
0 100 20
0 100 20
0 100 20
Each queue can Each queue can
burst to the full burst to 1/5
available capacity. the available
capacity.
[100/5=20]
Traffic in Q5 & Q3
Offered Default
Traffic H-Qos
40 100
0 60
20 60
0 40
0 40
Each queue
th
of can burst to the
available capacity
at that level. (full
capacity minus
capacity used by
higher levels)
QoS Scheduler Policies
Second
Pass (LUB)
59.39=40+19.39
0.39=0+0.39
39.42=20+19.42
0.39=0+0.39
0.39=0+0.39
Each queue can
burst to the used
capacity plus its
allocated part of
the unused
capacity.
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