The default dot1p priority-queue assignments are applied as follows:Dell(conf)#do show qos dot1p-queue-mappingDot1p Priority : 0 1 2 3 4 5 6 7Queue : 1 0 2 3 4 5 6 7PFC 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.Configuring Priority-Based Flow ControlPriority-Based Flow Control (PFC) provides a flow control mechanism based on the 802.1p priorities in converged Ethernet traffic receivedon 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 allowsnetwork administrators to create zero-loss links for Storage Area Network (SAN) traffic that requires no-drop service, while retainingpacket-drop congestion management for Local Area Network (LAN) traffic.To configure PFC, follow these steps:1 Create a DCB Map.CONFIGURATION modedcb-map dcb-map-nameThe dcb-map-name variable can have a maximum of 32 characters.2 Create a PFC group.CONFIGURATION modepriority-group group-num {bandwidth bandwidth | strict-priority} pfc onThe 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_numPriority 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 dot1ppriorities 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 dot1ppriorities 5, 6, and 7.Dell Networking OS Behavior: As soon as you apply a DCB policy with PFC enabled on an interface, DCBx starts exchanging informationwith PFC-enabled peers. The IEEE802.1Qbb, CEE, and CIN versions of PFC Type, Length, Value (TLV) are supported. DCBx also validatesPFC configurations that are received in TLVs from peer devices.252 Data Center Bridging (DCB)
