Concept Guide

ETS Conguration Notes
ETS provides a way to optimize bandwidth allocation to outbound 802.1p classes of converged Ethernet trac. Dierent trac types have
dierent service needs. Using ETS, you can create groups within an 802.1p priority class to congure dierent treatment for tracs with
dierent bandwidth, latency, and best-eort needs.
When you congure ETS in a DCB map:
• The DCB map associates a priority group with a PFC operational mode (on or o) and an ETS scheduling and bandwidth allocation. You
can apply a DCB map on multiple egress ports.
• Use the ETS conguration associated with 802.1p priority trac in a DCB map in DCBx negotiation with ETS peers.
• Trac in priority groups is assigned to strict-queue or weighted round-robin (WRR) scheduling in an ETS conguration and is managed
using the ETS bandwidth-assignment algorithm. Dell Networking OS de-queues all frames of strict-priority trac before servicing any
other queues. A queue with strict-priority trac 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 trac on Dell Networking OS is redirected to control
queues as higher priority trac with strict priority scheduling. After the control queues drain out, the remaining data trac is scheduled
to queues according to the bandwidth and scheduler conguration in the DCB map. The available bandwidth calculated by the ETS
algorithm is equal to the link bandwidth after scheduling non-ETS higher-priority trac.
• The conguration 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 congure 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 trac: dot1p priority trac on the switch is scheduled to the current queue mapping. dot1p priorities within the
same queue must have the same trac properties and scheduling method.
• ETS conguration error: If an error occurs in an ETS conguration, the conguration 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 conguration, the port’s conguration resets to the ETS conguration in the previously
congured 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 conguration only by using a DCB map.
The following prerequisites and restrictions apply when you congure ETS bandwidth allocation or strict-priority queuing in a DCB map:
• When allocating bandwidth or conguring 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 notication (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 conguration in the QoS output policy must take into account the bandwidth allocation or queue scheduler congured 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).
Data Center Bridging (DCB)
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