Reference Guide

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 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 an S6000 switch, ETS is enabled by default on Ethernet ports with equal bandwidth assigned to each 802.1p priority. 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 (see Configuring Bandwidth Allocation for DCBx CIN) 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.
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.
Data Center Bridging (DCB)
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