Owner`s manual

Data Center Bridging (DCB) | 53
Figure 5-2. Enhanced Transmission Selection
ETS uses the following traffic groupings to select multiprotocol traffic for transmission:
• 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 FTOS, 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 IEEE802.1azd2.5.
Configuring Enhanced Transmission Selection
Enhanced transmission selection (ETS) provides a way to optimize bandwidth allocation to outbound
802.1p classes of converged Ethernet traffic.