Concept Guide

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. 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 in a Trac Flow
The following gure shows how DCB handles a trac ow on an interface.
Figure 31. DCB PFC and ETS Trac Handling
Buer Organization
This section describes the buer organization on the platform.
A single chip architecture can allocate or share all its resource on all the ports. However, the system runs on a dierent 2x2 chip design.
In this design, all ports are assigned to four port-sets. These sets are built as follows:
• A or B for ingress, referred to as layers
• R or S for egress, referred to as slices
There are 4 XPEs with each XPE containing 4MB of buer space making the total available buer space to be 16MB. Out of these 4 XPEs,
one of the XPE is used for a particular trac ow based on its ingress and egress port pipes. For example, if a trac ow enters through a
port that is a part of the ingress pipe 0 and exits through a port that is part of the egress pipe 0, then XPE A from MMU Slice R is used. If a
trac ow enters through the pipe 1 and exits through the pipe 3, then XPE B from MMU Slice S is used.
The following example shows default DCB buer values:
DellEMC#
DellEMC#show dcb
Data Center Bridging (DCB)
273