Dell C1048P Port Extender Networking Configuration Guide for the C9000 Series - Page 279

Field Peer DCBx Status: Acknowledgment Number Total DCBx Frames transmitted Total DCBx Frames received Total DCBx Frame errors Total DCBx Frames unrecognized Description Acknowledgement number transmitted in Control TLVs received from peer device. Number of DCBx frames sent from local port. Number of DCBx frames received from remote peer port. Number of DCBx frames with errors received. Number of unrecognizable DCBx frames received. Performing PFC Using DSCP Bits Instead of 802.1p Bits Priority based Flow Control (PFC) is currently supported on Dell Networking OS for tagged packets based on the packet Dot1p. In certain data center deployments, VLAN configuration is avoided on the servers and all packets from the servers are untagged. These packets will carry IP header and can be differentiated based on the DSCP fields they carry on the server facing switch ports. Requirement is to classify these untagged packets from the server based on their DSCP and provide PFC treatment. Dell Networking OS Releases 9.3(0.0) and earlier provide CLI support to specify the priorities for which PFC is enabled on each port. This feature is applicable only for the tagged packets based on the incoming packet Dot1p and Dot1p based queue classification. This document will discuss the configurations required to support PFC for untagged packets based on incoming packet DSCP. For the tagged packets, Queue is selected based on the incoming Packet Dot1p. When PFC frames for a specific priority is received from the peer switch, the queue corresponding to that Dot1p is halted from scheduling on that port, thus honoring the PFC from the peer. If a queue is congested due to packets with a specific Dot1p and PFC is enabled for that Dot1p, switch will transit out PFC frames for that Dot1p. The packet Dot1p to Queue mapping for classification on the ingress must be same as the mapping of Dot1p to the Queue to be halted on the egress used for PFC honoring. Dell Networking OS ensures that these mappings are identical. This section discusses the Dell Networking OS configurations needed for above PFC generation and honoring mechanism to work for the untagged packets. PRIORITY to PG mapping (PRIO2PG) is on the ingress for each port. By default, all priorities are mapped to PG7. A priority for which PFC has to be generated is assigned to a PG other than PG7 (say PG6) and buffer watermark is set on PG6 so as to generate PFC. In ingress, the buffers are accounted at per PG basis and would indicate the number of the packets that has ingress this port PG but still queued up in egress pipeline. However, there is no direct mapping between the PG and Queue. Packet is assigned an internal priority on the ingress pipeline based on the queue to which it is destined. This Internal-priority to Queue mapping has been modified and enhanced as follows for the device: PFC and ETS Configuration Examples This section contains examples of how to configure and apply DCB policies on an interface. Using PFC and ETS to Manage Data Center Traffic The following shows examples of using PFC and ETS to manage your data center traffic. In the following example: • Incoming SAN traffic is configured for priority-based flow control. • Outbound LAN, IPC, and SAN traffic is mapped into three ETS priority groups and configured for enhanced traffic selection (bandwidth allocation and scheduling). Data Center Bridging (DCB) 279