Configuring Priority-Based Flow Control - Dell C9000 Series Networking Configuration Manual

• If you configure more than one priority group as strict priority, the higher numbered priority queue is
given preference when scheduling data traffic.
Configuring Priority-Based Flow
Control
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 (Class of Service (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 is to be stopped. Data Center Bridging Exchange protocol (DCBx) provides the link-level exchange
of PFC parameters between peer devices. PFC allows network administrators to create zero-loss links for
Storage Area Network (SAN) traffic that requires no-drop service, while retaining packet-drop congestion
management for Local Area Network (LAN) traffic.
To configure PFC, follow these steps.
1 Create a DCB Map.
CONFIGURATION mode
dcb-map dcb-map-name
The dcb-map-name variable can have a maximum of 32 characters.
2 Create a priority group.
CONFIGURATION mode
priority-group group-num {bandwidth bandwidth | strict-priority} [[committed |
peak] bandwidth [burst-size] [peak | committed] bandwidth [burst-size]] pfc {on
| off}
The range for priority group is from 0 to 7.
Set the bandwidth in percentage. The percentage range is from 1 to 100% in units of 1%.
Committed and peak bandwidth is in megabits per second. The range is from 0 to 40000.
Committed and peak burst size is in kilobytes. Default is 50. The range is from 0 to 10000.
The pfc on command enables priority-based flow control.
3 Specify the dot1p priority-to-priority group mapping for each priority.
priority-pgid dot1p0_group_num dot1p1_group_num ...dot1p7_group_num
Priority group range is from 0 to 7. All priorities that map to the same queue must be in the same priority
group.
Data Center Bridging (DCB) 306