Reference Guide

– No bandwidth limit or no ETS processing
• Bandwidth allocated by the ETS algorithm is made available after strict-priority groups are serviced.
Bandwidth is distributed in the following ways:
– If bandwidth is not assigned to the priority groups, all available bandwidth is equally distributed
among the priority groups. For example, if there are two priority groups, each will be assigned 50%
of the available bandwidth; if there are four priority groups, each group is assigned 25% of the
available bandwidth so that bandwidth use is always 100%.
– 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 is less than 100%, all configured priority group bandwidth is
incremented based on the configured percentage ratio until all priority group 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 greater than or equal to 100% and any default priority groups
exist, then 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%.
NOTE: You must configure at least one ETS priority group to a DCB output policy.
• 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 the S4810; ETS is also
disabled.
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 information, refer to Link Layer Discovery Protocol (LLDP). The following LLDP TLVs are supported
for DCB parameter exchange:
PFC
parameters
PFC Configuration TLV and Application Priority Configuration TLV.
ETS parameters ETS Configuration TLV and ETS Recommendation TLV.
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Data Center Bridging (DCB)