Ets Prerequisites And Restrictions; Priority-Group Configuration Notes - Dell C9000 Series Networking Configuration Manual

• Dell Networking OS supports hierarchical scheduling on an interface. The control traffic on Dell
Networking OS is redirected to control queues as higher priority traffic with strict priority scheduling.
After the control queues drain out, the remaining data traffic is scheduled to queues according to the
bandwidth and scheduler configuration in the DCB map. The available bandwidth calculated by the ETS
algorithm is equal to the link bandwidth after scheduling non-ETS higher-priority traffic.
• The configuration of bandwidth allocation and strict-queue scheduling is not supported at the same
time for a priority group.
• Bandwidth assignment: By default, equal bandwidth is assigned to each dot1p priority in a priority
group. To configure the bandwidth assigned to the port queues associated with dot1p priorities in a
priority group, use the bandwidth percentage parameter. The sum of the bandwidth allocated to all
priority groups in a DCB map must be 100% of the bandwidth on the link. You must allocate at least 1%
of the total bandwidth to each priority group.
• Scheduling of priority traffic: dot1p priority traffic on the switch is scheduled to the current queue
mapping. dot1p priorities within the same queue must have the same traffic properties and scheduling
method.
• ETS configuration error: If an error occurs in an ETS configuration, the configuration is ignored and the
scheduler and bandwidth allocation settings are reset to the ETS default value: 100% of available
bandwidth is allocated to priority group 0 and the bandwidth is equally assigned to each dot1p priority.
If an error occurs when a port receives a peer's ETS configuration, the port's configuration resets to the ETS
configuration in the previously configured DCB map. If no DCB map was previously applied, the port resets to
the default ETS parameters.

ETS Prerequisites and Restrictions

On the switch, ETS is enabled by default on Ethernet ports with equal bandwidth assigned to each 802.1p
priority, when DCB is enabled. You can change the default ETS configuration only by using a DCB map.
The following prerequisites and restrictions apply when you configure ETS bandwidth allocation or strict-
priority queuing in a DCB map:
• When allocating bandwidth or configuring strict-priority queuing for dot1p priorities in a priority group
on a DCBx CIN interface, take into account the CIN bandwidth allocation and dot1p-queue mapping.
• Although ETS bandwidth allocation or strict-priority queuing does not support weighted random early
detection (WRED), explicit congestion notification (ECN), rate shaping, and rate limiting because these
parameters are not negotiated by DCBx with peer devices, you can apply a QoS output policy with
WRED and/or rate shaping on a DCBx CIN-enabled interface. In this case, the WRED or rate shaping
configuration in the QoS output policy must take into account the bandwidth allocation or queue
scheduler configured in the DCB map.
• ETS is not supported on PE ports and C9010 cascade ports (member ports in the C9010 LAG created to
connect to an attached C1048P).

Priority-Group Configuration Notes

When you configure priority groups in a DCB map:
• A priority group consists of 802.1p priority values that are grouped together for similar bandwidth
allocation and scheduling, and that share the same latency and loss requirements. All 802.1p priorities
mapped to the same queue must be in the same priority group.
• In a DCB map, each 802.1p priority must map to a priority group.
• The maximum number of priority groups supported in a DCB map on an interface is equal to 3. Each
priority group can support more than one data queue.
Data Center Bridging (DCB) 305