Addendum

Step Task Command Command Mode
already configured for PFC using the pfc
priority command.
Range: 0-3. Separate queue values with a
comma; specify a priority range with a dash;
for example: pfc no-drop queues 1,3 or pfc
no-drop queues 2-3 Default: No lossless
queues are configured.
Data Center Bridging: Default Configuration
This functionality is supported on the S6000 platform.
Before you configure PFC and ETS on an S5000 switch (see Configuring DCB Maps and its Attributes),
take into account the following default settings:
DCB is enabled (see Enabling Data Center Bridging).
The PFC memory buffer supports up to 64 PFC-enabled ports and two lossless queues per port.
PFC and ETS are globally enabled by default:
The default dot1p priority-queue assignments are applied as follows:
802.1p value in incoming frame: 0 1 2 3 4 5 6 7
Egress queue assignment 0 0 0 1 2 3 3 3
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 S5000 interface, you must specify a PFC mode and ETS
bandwidth allocation for a priority group and an 802.1p priority-to-priority group mapping in a DCB map
(see Configuring PFC and ETS in a DCB Map). No default PFC and ETS settings are applied to Ethernet
interfaces.
Configuring PFC and ETS in a DCB Map
An S6000 switch supports the use of a DCB map in which you configure priority-based flow control and
enhanced transmission selection settings. To configure PFC and ETS parameters, you must apply a DCB
map on an S6000 interface. This functionality is supported on the S6000 platform.
PFC Configuration Notes
Priority-based flow control (PFC) provides a flow control mechanism based on the 802.1p priorities in
converged Ethernet traffic received on an interface and is enabled by default when you enable DCB. As
an enhancement to the existing Ethernet pause mechanism, 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 an S6000 switch, PFC is enabled by default 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 DCB Maps and its Attributes.
536
Data Center Bridging (DCB)