Dell S4048T, Configuration Manual

Page: 317 / 1277

Priority group 1 Assigns traffic to one priority queue with 20% of the link bandwidth and strict-priority
scheduling.
Priority group 2 Assigns traffic to one priority queue with 30% of the link bandwidth.
Priority group 3 Assigns traffic to two priority queues with 50% of the link bandwidth and strict-priority
scheduling.
In this example, the configured ETS bandwidth allocation and scheduler behavior is as follows:
Unused bandwidth
usage: Normally, if there is no traffic or unused bandwidth for a priority group, the bandwidth
allocated to the group is distributed to the other priority groups according to the
bandwidth percentage allocated to each group. However, when three priority groups
with different bandwidth allocations are used on an interface:
• If priority group 3 has free bandwidth, it is distributed as follows: 20% of the free
bandwidth to priority group 1 and 30% of the free bandwidth to priority group 2.
• If priority group 1 or 2 has free bandwidth, (20 + 30)% of the free bandwidth is
distributed to priority group 3. Priority groups 1 and 2 retain whatever free
bandwidth remains up to the (20+ 30)%.
Strict-priority
groups: If two priority groups have strict-priority scheduling, traffic assigned from the priority
group with the higher priority-queue number is scheduled first. However, when three
priority groups are used and two groups have strict-priority scheduling (such as groups
1 and 3 in the example), the strict priority group whose traffic is mapped to one queue
takes precedence over the strict priority group whose traffic is mapped to two queues.
Therefore, in this example, scheduling traffic to priority group 1 (mapped to one strict-priority queue) takes
precedence over scheduling traffic to priority group 3 (mapped to two strict-priority queues).
Using ETS to Manage Converged
Ethernet Traffic
To use ETS for managing converged Ethernet traffic, use the following command:
dcb-map stack-unit all dcb-map-name
Applying DCB Policies in a Switch Stack
You can apply DCB policies with PFC and ETS configurations to all stacked ports in a switch stack or on a
stacked switch.
To apply DCB policies in a switch stack, follow this step.
• Apply the specified DCB policy on all ports of the switch stack or a single stacked switch.
CONFIGURATION mode
dcb-map {stack-unit all | stack-ports all} dcb-map-name
Data Center Bridging (DCB) 317