Administrator Guide

priorities configured). If you do not enable PFC on an interface, you can enable the 802.3x link-
level pause function. By default, the link-level pause is disabled, when you disable DCBx and PFC. If
no PFC dcb-map has been applied on the interface, the default PFC settings are used.
• PFC supports buffering to receive data that continues to arrive on an interface while the remote system
reacts to the PFC operation.
• PFC uses the DCB MIB IEEE802.1azd2.5 and the PFC MIB IEEE802.1bb-d2.2.
If DCBx negotiation is not successful (for example, due to a version or TLV mismatch), DCBx is disabled and
you cannot enable PFC or ETS.
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 29. Enhanced Transmission Selection
The following table lists the traffic groupings ETS uses to select multiprotocol traffic for transmission.
Data Center Bridging (DCB) 278