Administrator Guide

Table 11. 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
traffic in a group must have the same traffic handling
requirements for latency and frame loss.
Group ID A 4-bit identifier 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
• No bandwidth limit or no ETS processing
• Bandwidth allocated by the ETS algorithm is made available after strict-priority groups are serviced. If a
priority group does not use its allocated bandwidth, the unused bandwidth is made available to other
priority groups so that the sum of the bandwidth use is 100%. If priority group bandwidth use exceeds
100%, all configured priority group bandwidth is decremented based on the configured percentage ratio
until all priority group bandwidth use is 100%. If priority group bandwidth usage is less than or equal to
100% and any default priority groups exist, a minimum of 1% bandwidth use is assigned by decreasing 1%
of bandwidth from the other priority groups until priority group bandwidth use is 100%.
• For ETS traffic selection, an algorithm is applied to priority groups using:
• Strict priority shaping
• ETS shaping
• (Credit-based shaping is not supported)
• ETS uses the DCB MIB IEEE 802.1azd2.5.
Data Center Bridging Exchange
Protocol (DCBx)
The data center bridging exchange (DCBx) protocol is disabled by default on any switch on which PFC or ETS
are enabled.
DCBx allows a switch to automatically discover DCB-enabled peers and exchange configuration information.
PFC and ETS use DCBx to exchange and negotiate parameters with peer devices. DCBx capabilities include:
• Discovery of DCB capabilities on peer-device connections.
• Determination of possible mismatch in DCB configuration on a peer link.
• Configuration of a peer device over a DCB link.
DCBx requires the link layer discovery protocol (LLDP) to provide the path to exchange DCB parameters with
peer devices. Exchanged parameters are sent in organizationally specific TLVs in LLDP data units. For more
Data Center Bridging (DCB) 279