Administrator Guide

• PFC uses the DCB MIB IEEE802.1azd2.5 and the PFC MIB IEEE802.1bb-d2.2.
Enhanced Transmission Selection
Enhanced transmission selection (ETS) supports optimized bandwidth allocation between trac types in multiprotocol (Ethernet,
FCoE, SCSI) links.
ETS allows you to divide trac according to its 802.1p priority into dierent priority groups (trac classes) and congure bandwidth
allocation and queue scheduling for each group to ensure that each trac type is correctly prioritized and receives its required
bandwidth. For example, you can prioritize low-latency storage or server cluster trac in a trac class to receive more bandwidth
and restrict best-eort LAN trac assigned to a dierent trac class.
Although you can congure strict-priority queue scheduling for a priority group, ETS introduces exibility that allows the bandwidth
allocated to each priority group to be dynamically managed according to the amount of LAN, storage, and server trac in a ow.
Unused bandwidth is dynamically allocated to prioritized priority groups. Trac is queued according to its 802.1p priority assignment,
while exible bandwidth allocation and the congured queue-scheduling for a priority group is supported.
The following gure shows how ETS allows you to allocate bandwidth when dierent trac types are classed according to 802.1p
priority and mapped to priority groups.
Figure 142. Enhanced Transmission Selection
The following table lists the trac groupings ETS uses to select multiprotocol trac for transmission.
Table 77. ETS Trac Groupings
Trac Groupings Description
Priority group A group of 802.1p priorities used for bandwidth allocation and
queue scheduling. All 802.1p priority trac in a group must have
the same trac handling requirements for latency and frame
loss.
Group ID A 4-bit identier assigned to each priority group. The range is
from 0 to 7.
Group bandwidth Percentage of available bandwidth allocated to a priority group.
Group transmission selection algorithm (TSA) Type of queue scheduling a priority group uses.
In the Dell Networking OS, ETS is implemented as follows:
• ETS supports groups of 802.1p priorities that have:
– PFC enabled or disabled
900
FC Flex IO Modules