Enhanced Transmission Selection - Dell S4048T Configuration Manual

• PFC uses DCB MIB IEEE 802.1azd2.5 and PFC MIB IEEE 802.1bb-d2.2.
• A dynamic threshold handles intermittent traffic bursts and varies based on the number of PFC priorities
contending for buffers, while a static threshold places an upper limit on the transmit time of a queue
after receiving a message to pause a specified priority. PFC traffic is paused only after surpassing both
static and dynamic thresholds for the priority specified for the port.
• By default, PFC is enabled when you enable DCB. If you have not loaded FCoE_DCB_Config and
iSCSI_DCB_Config, DCB is disabled. When you enable DCB globally, you cannot simultaneously enable
link-level flow control.
• Buffer space is allocated and de-allocated only when you configure a PFC priority on the port.

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.
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 33. Enhanced Transmission Selection
The following table lists the traffic groupings ETS uses to select multiprotocol traffic for transmission.
Table 16. ETS Traffic Groupings
Traffic Groupings
Group ID
Description
A 4-bit identifier assigned to each priority group. The
range is from 0 to 7 configurable; 8 - 14 reservation
and 15.0 - 15.7 is strict priority group..
Data Center Bridging (DCB) 296