Owners Manual

• In a switch stack, configure all stacked ports with the same PFC configuration.
• Dell Networking OS allows you to change the default dot1p priority-queue assignments only if the
change satisfies the following requirements in DCB maps already applied to S6000 interfaces:
• All 802.1p priorities mapped to the same queue must be in the same priority group.
• A maximum of two PFC-enabled, lossless queues are supported on an interface.
Otherwise, the reconfiguration of a default dot1p-queue assignment is rejected.
• To ensure complete no-drop service, apply the same PFC parameters on all PFC-enabled peers.
PFC Prerequisites and Restrictions
On an S6000 switch, PFC is globally enabled by default, but not applied on specific 802.1p priorities. To
enable PFC on 802.1p priorities, create a DCB map.
The following prerequisites and restrictions apply when you configure PFC in a DCB map:
• You can enable PFC on a maximum of two priority queues on an interface. Enabling PFC for dot1p
priorities configures the corresponding port queue as lossless.
• You cannot enable PFC and link-level flow control at the same time on an interface.
ETS Configuration Notes
ETS provides a way to optimize bandwidth allocation to outbound 802.1p classes of converged Ethernet
traffic. Different traffic types have different service needs. Using ETS, you can create groups within an
802.1p priority class to configure different treatment for traffics with different bandwidth, latency, and
best-effort needs.
When you configure ETS in a DCB map:
• The DCB map associates a priority group with a PFC operational mode (on or off) and an ETS
scheduling and bandwidth allocation. You can apply a DCB map on multiple egress ports.
• Use the ETS configuration associated with 802.1p priority traffic in a DCB map in DCBx negotiation
with ETS peers.
• Traffic in priority groups is assigned to strict-queue or weighted round-robin (WRR) scheduling in an
ETS configuration and is managed using the ETS bandwidth-assignment algorithm. Dell Networking
OS de-queues all frames of strict-priority traffic before servicing any other queues. A queue with
strict-priority traffic can starve other queues in the same port.
• ETS-assigned bandwidth allocation and strict-priority scheduling apply only to data queues, not to
control queues.
• 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
Data Center Bridging (DCB)
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