Users Guide

Table 17. XPE Numbering on Dell EMC Networking OS (continued)
XPE Numbering
XPE A of MMU Slice S 0.1
XPE B of MMU Slice R 0.2
XPE B of MMU Slice S 0.3
Enabling Data Center Bridging
DCB is automatically configured when you configure FCoE or iSCSI optimization.
Data center bridging supports converged enhanced Ethernet (CEE) in a data center network. DCB is disabled by default. It must
be enabled to support CEE.
● Priority-based flow control
● Enhanced transmission selection
● Data center bridging exchange protocol
● FCoE initialization protocol (FIP) snooping
DCB processes virtual local area network (VLAN)-tagged packets and dot1p priority values. Untagged packets are treated with a
dot1p priority of 0.
For DCB to operate effectively, you can classify ingress traffic according to its dot1p priority so that it maps to different data
queues. The dot1p-queue assignments used are shown in the following table.
To enable DCB, enable either the iSCSI optimization configuration or the FCoE configuration.
NOTE:
Dell EMC Networking OS Behavior: DCB is not supported if you enable link-level flow control on one or more
interfaces. For more information, refer to Ethernet Pause Frames.
DCB Maps and its Attributes
This topic contains the following sections that describe how to configure a DCB map, apply the configured DCB map to a port,
configure PFC without a DCB map, and configure lossless queues.
DCB Map: Configuration Procedure
A DCB map consists of PFC and ETS parameters. By default, PFC is not enabled on any 802.1p priority and ETS allocates equal
bandwidth to each priority. To configure user-defined PFC and ETS settings, you must create a DCB map. The following is an
overview of the steps involved in configuring DCB.
● Enter global configuration mode to create a DCB map or edit PFC and ETS settings.
● Configure the PFC setting (on or off) and the ETS bandwidth percentage allocated to traffic in each priority group, or
whether the priority group traffic should be handled with strict priority scheduling. You can enable PFC on a maximum of
two priority queues on an interface. Enabling PFC for dot1p priorities makes the corresponding port queue lossless. The
sum of all allocated bandwidth percentages in all groups in the DCB map must be 100%. Strict-priority traffic is serviced
first. Afterwards, you can configure either the peak rates or the committed rates. The bandwidth allocated to other priority
groups is made available and allocated according to the specified percentages. If a priority group does not use its allocated
bandwidth, the unused bandwidth is made available to other priority groups.
● Repeat the above procedure to configure PFC and ETS traffic handling for each priority group
● Specify the dot1p priority-to-priority group mapping for each priority. The priority group range is from 0 to 7. All priorities
that map to the same queue must be in the same priority group.
Leave a space between each priority group number. For example: priority-pgid 0 0 0 1 2 4 4 4 in which priority group 0
maps to dot1p priorities 0, 1, and 2; priority group 1 maps to dot1p priority 3; priority group 2 maps to dot1p priority 4; priority
group 4 maps to dot1p priorities 5, 6, and 7.
Data Center Bridging (DCB)
249