The maximum number of lossless queues globally supported on the switch is two.The range is from 0 to 7. Separate the queue values with a comma; specify a priority range with adash; for example, pfc no-drop queues 1,7 or pfc no-drop queues 2-7.The default: No lossless queues are configured.NOTE: Dell Networking OS Behavior: By default, no lossless queues are configured on a port.A limit of two lossless queues is supported on a port. If the amount of priority traffic that you configure tobe paused exceeds the two lossless queues, an error message displays.In S6000, any pfc-dot1p priorities configured on a given interface need not be the same across thesystem. In other words, lossless queue limit is applicable on a per-port level and not on the global-configcontext. For example, one of the Te/Fo interfaces can have pfc-dot1p priorities as 2 and 3. Whereas, theother Te/Fo interface(s) can have its pfc-dot1p priorities as 4 and 5.It is the user responsibility to have symmetric PFC configurations on the interfaces involved in a particularPFC-enabled traffic-flow to obtain lossless behavior.Configuring PFC in a DCB MapAn S6000–ON switch supports the use of a DCB map in which you configure priority-based flow control(PFC) setting. To configure PFC parameters, you must apply a DCB map on an S6000–ON interface. Thisfunctionality is supported on the S6000–ON platform.PFC Configuration NotesPFC provides flow control based on the 802.1p priorities in a converged Ethernet traffic that is receivedon an interface and is enabled by default when you enable DCB. As an enhancement to the existingEthernet pause functionality, PFC stops traffic transmission for specified priorities (CoS values) withoutimpacting 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 ofthe traffic that needs to be stopped. DCBx provides the link-level exchange of PFC parameters betweenpeer 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 switch, PFC is enabled by default on Ethernet ports (pfc mode on command). You can configurePFC parameters using a DCB map or the pfc priority command in Interface configuration mode. Formore information, see Configuring Priority-Based Flow Control.As soon as you apply a DCB map with PFC enabled on an interface, DCBx starts exchanging informationwith a peer. The IEEE802.1Qbb, CEE and CIN versions of PFC TLV are supported. DCBx also validates PFCconfigurations that are received in TLVs from peer devices. By applying a DCB map with PFC enabled,you enable PFC operations on ingress port traffic. To achieve complete lossless handling of traffic,configure PFC priorities on all DCB egress ports.When you apply or remove a DCB input policy from an interface, one or two CRC errors are expected tobe noticed on the ingress ports for each removal or attachment of the policy. This behavior occursbecause the port is brought down when PFC is configured. When a DCB input policy with PFC profile isconfigured or unconfigured on an interface or a range of interfaces not receiving any traffic, interfaces246 Data Center Bridging (DCB)
