Reference Guide

(2) of lossless queues supported globally on the switch. In this case, all PFC configurations received from

PFC-enabled peers are removed and resynchronized with the peer devices.

Traffic may be interrupted when you reconfigure PFC no-drop priorities in an input policy or reapply the

policy to an interface.

Enhanced Transmission Selection

Enhanced transmission selection (ETS) supports optimized bandwidth allocation between traffic types in

multiprotocol (Ethernet, FCoE, SCSI) links.

ETS allows you to divide traffic according to its 802.1p priority into different priority groups (traffic

classes) and configure bandwidth allocation and queue scheduling for each group to ensure that each

traffic type is correctly prioritized and receives its required bandwidth. For example, you can prioritize

low-latency storage or server cluster traffic in a traffic class to receive more bandwidth and restrict best-

effort LAN traffic assigned to a different traffic class.

Although you can configure strict-priority queue scheduling for a priority group, ETS introduces flexibility

that allows the bandwidth allocated to each priority group to be dynamically managed according to the

amount of LAN, storage, and server traffic in a flow. Unused bandwidth is dynamically allocated to

prioritized priority groups. Traffic is queued according to its 802.1p priority assignment, while flexible

bandwidth allocation and the configured queue-scheduling for a priority group is supported.

The following figure shows how ETS allows you to allocate bandwidth when different traffic types are

classed according to 802.1p priority and mapped to priority groups.

Figure 2. Enhanced Transmission Selection

The following table lists the traffic groupings ETS uses to select multiprotocol traffic for transmission.

Table 2. ETS Traffic Groupings

Traffic Groupings Description

Priority group A group of 802.1p priorities used for bandwidth

allocation and queue scheduling. All 802.1p priority

Data Center Bridging (DCB)