Administrator Guide

Applying a DCB Map on a Line Card
On the C9010, DCB is supported per-line card. If the traffic handled by a DCB map is transmitted on ports on different line cards, you
must manually configure the DCB map on the backplane ports of the C9010 line cards on which the ports reside.
• Apply a DCB map with PFC and ETS settings on the backplane ports of C9010 line cards.
CONFIGURATION mode
dcb-map {linecard {0-11 | all} [port-set {0-3 | all}] backplane all dcb-map-name
NOTE: On the C9010, linecard 10 and linecard 11 correspond to RPM0 and RPM1 respectively. To enable DCB
across C9010 line cards, apply a DCB map on all installed line cards (linecard 0–9) and RPMs (linecard 10–11).
NOTE: If the DCB map you apply to the backplane ports of C9010 RPMs (linecard 10–11) configures two or more
priority groups, you must increase the size of the PFC shared and total buffers (dcb pfc-shared-buffer-size
and dcb pfc-total-buffer-size commands).
Data Center Bridging: Default Configuration
Before you configure PFC and ETS on a switch see the priority group setting taken into account the following default settings:
• DCB is enabled.
• The PFC memory buffer supports up to 2 lossless queues per port on all PFC enabled ports.
• PFC and ETS are globally enabled by default.
The default dot1p priority-queue assignments are applied as follows:
Dell(conf)#do show qos dot1p-queue-mapping
Dot1p Priority : 0 1 2 3 4 5 6 7
Queue : 1 0 2 3 4 5 6 7
Dell(conf)#
Dell(conf)#dcb enable pfc-queues ?
<1-4> Number of PFC lossless queues(default=2)
<1-4> Number of PFC lossless queues(default=2)
NOTE: In Egress queue assignment (8 queues).
PFC is not applied on specific dot1p priorities.
ETS: Equal bandwidth is assigned to each port queue and each dot1p priority in a priority group.
To configure PFC and ETS parameters on an interface, you must specify the PFC mode, the ETS bandwidth allocation for a priority group,
and the 802.1p priority-to-priority group mapping in a DCB map. No default PFC and ETS settings are applied to Ethernet interfaces.
Configuration Notes: PFC and ETS in a DCB Map
The switch supports the use of a DCB map in which you configure priority-based flow control (PFC) and enhanced transmission selection
(ETS) settings. To configure PFC and ETS parameters, you must apply a DCB map on the interface.
PFC Configuration Notes
PFC provides flow control based on the 802.1p priorities in a converged Ethernet traffic that is received on an interface and is enabled
when you enable DCB. As an enhancement to the existing Ethernet pause functionality, PFC stops traffic transmission for specified
priorities (CoS values) without impacting other priority classes. Different traffic types are assigned to different priority classes.
When traffic congestion occurs, PFC sends a pause frame to a peer device with the CoS priority values of the traffic that needs to be
stopped. DCBx provides the link-level exchange of PFC parameters between peer devices. PFC allows network administrators to create
zero-loss links for SAN traffic that requires no-drop service, while at the same time retaining packet-drop congestion management for
LAN traffic.
On the switch, PFC is enabled on Ethernet ports (pfc mode on command). You can configure PFC parameters using a DCB map or the
pfc priority command in Interface configuration mode. For more information, see Configuring Priority-Based Flow Control.
Data Center Bridging (DCB)
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