Concept Guide

• All 802.1p priorities are enabled for PFC. Queues to which PFC priority trac is mapped are lossless by default. Trac may be

interrupted due to an interface ap (going down and coming up).

• For PFC to be applied on an Aggregator port, the auto-congured priority trac must be supported by a PFC peer (as detected by

DCBx).

• A dcb-map for PFC applied to an interface may become invalid if dot1p-queue mapping is recongured. This situation occurs when the

new dot1p-queue assignment exceeds the maximum number (2) of lossless queues supported globally on the switch. In this case, all

PFC congurations received from PFC-enabled peers are removed and re-synchronized with the peer devices.

• Dell Networking OS does not support MACsec Bypass Capability (MBC).

Conguring Enhanced Transmission Selection

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c with dierent bandwidth, latency, and best-eort needs.

For example, storage trac is sensitive to frame loss; interprocess communication (IPC) trac is latency-sensitive. ETS allows dierent

trac types to coexist without interruption in the same converged link by:

• Allocating a guaranteed share of bandwidth to each priority group.

• Allowing each group to exceed its minimum guaranteed bandwidth if another group is not fully using its allotted bandwidth.

To congure ETS and apply an ETS output policy to an interface, you must:

1 Create a Quality of Service (QoS) output policy with ETS scheduling and bandwidth allocation settings.

2 Create a priority group of 802.1p trac classes.

3 Congure a DCB output policy in which you associate a priority group with a QoS ETS output policy.

4 Apply the DCB output policy to an interface.

How Enhanced Transmission Selection is Implemented

Enhanced transmission selection (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, groups within an 802.1p priority class are auto-congured to provide

dierent treatment for trac with dierent bandwidth, latency, and best-eort needs.

For example, storage trac is sensitive to frame loss; interprocess communication (IPC) trac is latency-sensitive. ETS allows dierent

trac types to coexist without interruption in the same converged link.

NOTE

: The IEEE 802.1Qaz, CEE, and CIN versions of ETS are supported.

ETS is implemented on an Aggregator as follows:

• Trac in priority groups is assigned to strict-queue or WERR scheduling in a dcb-map and is managed using the ETS bandwidth-

assignment algorithm. Dell Networking OS de-qeues 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 scheduling apply only to data queues, not to control queues.

• Dell Networking OS supports hierarchical scheduling on an interface. Dell Networking OS control trac is redirected to control queues

as higher priority trac with strict priority scheduling. After 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.

• By default, equal bandwidth is assigned to each port queue and each dot1p priority in a priority group.

• By default, equal bandwidth is assigned to each priority group in the dcb-map applied to an egress port. The sum of auto-congured

bandwidth allocation to dot1p priority trac in all ETS priority groups is 100%.

• dot1p priority trac on the switch is scheduled according to the default dot1p-queue mapping. dot1p priorities within the same queue

should have the same trac properties and scheduling method.

• 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 should be in the same priority group.

Data Center Bridging (DCB)