Users Guide

Trac Groupings Description

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 congured priority group bandwidth is decremented based on the

congured 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 trac 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 conguration 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 conguration on a peer link.

• Conguration 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 specic 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 Conguration TLV and Application Priority Conguration TLV.

ETS parameters ETS Conguration TLV and ETS Recommendation TLV.

Data Center Bridging (DCB)