Dell MX5108n OS10 Enterprise Edition User Guide for PowerEdge MX IO Modules Re - Page 644

PFC configuration notes • PFC is supported for 802.1p priority traffic (dot1p 0 to 7). FCoE traffic traditionally uses dot1p priority 3 - iSCSI storage traffic uses dot1p priority 4. • Configure PFC for ingress traffic by using network-qos class and policy maps (see Quality of Service). The queues used for PFCenabled traffic are treated as lossless queues. Configure the same network-qos policy map on all PFC-enabled ports. Configure required bandwidth for lossless traffic using ETS queuing (output) policies on egress interfaces. • In a network-qos policy-class map, use commands to generate PFC pause frames for matching class-map priorities: - Send pause frames for matching class-map traffic during congestion (pause command). - (Optional) Enter user-defined values for the reserved ingress buffer-size of PFC class-map traffic, and the thresholds used to send XOFF and XON pause frames (pause [buffer-size kilobytes pause-threshold kilobytes resumethreshold kilobytes]command). - Configure the matching dot1p values used to send pause frames (pfc-cos command). - (Optional) Set the static and dynamic thresholds that determine the shared buffers available for PFC class-map traffic queues (queue-limit thresh-mode command). • By default, all ingress traffic is handled by the lossy ingress buffer. When you enable PFC, dot1p ingress traffic competes for shared buffers in the lossless pool instead of the shared lossy pool. The number of lossless queues supported on an interface depends on the amount of available free memory in the lossy pool. • Use the priority-flow-control mode on command to enable PFC for FCoE and iSCSI traffic (example, priority 3 and 4). • Enable DCBX on interfaces to detect and auto-configure PFC/ETS parameters from peers. • PFC and 802.3x link-level flow control (LLFC) are disabled by default on an interface. You cannot enable PFC and LLFC at the same time. LLFC ensures lossy traffic in best-effort transmission. Enable PFC to enable guarantee lossless FCoE and iSCSI traffic. PFC manages buffer congestion by pausing specified ingress dot1p traffic; LLFC pauses all data transmission on an interface. To enable LLFC, enter the flowcontrol [receive | transmit] [on | off] command. • SYSTEM-QOS mode applies a service policy globally on all interfaces: - Create and apply a 1-to-1 802.1p-priority-to-traffic-class mapping on an interface or all interfaces in INTERFACE or SYSTEM-QOS mode - Create and apply a 1-to-1 traffic-class-to-queue mapping on an interface or all interfaces in INTERFACE or SYSTEM-QOS mode Configure dot1p priority to traffic class mapping Decide if you want to use the default 802.1p priority-to-traffic class (qos-group) mapping or configure a new map. By default, the qos class-trust class map is applied to ingress traffic. Class-trust is a reserved class name. The class-trust class instructs OS10 interfaces to honor dot1p or DSCP traffic. Dot1p Priority : 0 1 2 3 4 5 6 7 Traffic Class : 1 0 2 3 4 5 6 7 1 Create a qos policy map and set its class to class-trust in CONFIGURATION mode. Enter POLICY-CLASS-MAP mode and specify that dot1p or DSCP values are trusted. policy-map type qos trust-policy-map-name class class-trust 644 Converged data center services