Concept Guide

ETS Operation with DCBx
The following section describes DCBx negotiation with peer ETS devices.
In DCBx negotiation with peer ETS devices, ETS conguration is handled as follows:
• ETS TLVs are supported in DCBx versions CIN, CEE, and IEEE2.5.
• The DCBx port-role congurations determine the ETS operational parameters (refer to Congure a DCBx Operation).
• ETS congurations received from TLVs from a peer are validated.
• If there is a hardware limitation or TLV error:
– DCBx operation on an ETS port goes down.
– New ETS congurations are ignored and existing ETS congurations are reset to the default ETS settings.
• ETS operates with legacy DCBx versions as follows:
– In the CEE version, the priority group/trac class group (TCG) ID 15 represents a non-ETS priority group. Any priority group
congured with a scheduler type is treated as a strict-priority group and is given the priority-group (TCG) ID 15.
Conguring ETS in a DCB Map
A switch supports the use of a DCB map in which you congure enhanced transmission selection (ETS) setting. To congure ETS
parameters, you must apply a DCB map on an interface.
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 EMC 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 EMC Networking OS supports hierarchical scheduling on an interface. The control trac on Dell EMC 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.
Data Center Bridging (DCB)
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