Configuring Pfc In A Dcb Map; Pfc Configuration Notes - Dell S4048T Configuration Manual

pfc no-drop queues queue-range
For the dot1p-queue assignments, refer to the dot1p Priority-Queue Assignment table.
The maximum number of lossless queues globally supported on the switch is two.
The range is from 0 to 3. Separate the queue values with a comma; specify a priority range with a dash;
for example, pfc no-drop queues 1,3 or pfc no-drop queues 2-3.
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 to be
paused exceeds the two lossless queues, an error message displays.

Configuring PFC in a DCB Map

A 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 interface.

PFC Configuration Notes

PFC provides flow control based on the 802.1p priorities in a converged Ethernet traffic that is received on an
interface and is enabled by default when you enable DCB. As an enhancement to the existing Ethernet pause
functionality, PFC stops traffic transmission for specified priorities (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 needs to be stopped. DCBx provides the link-level exchange of PFC parameters between peer
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 a switch, PFC is enabled by default on Ethernet ports (pfc mode on command). You can configure PFC
parameters using a DCB map or the pfc priority command in Interface configuration mode. For more
information, see Configuring Priority-Based Flow
As soon as you apply a DCB map with PFC enabled on an interface, DCBx starts exchanging information with
a peer. The IEEE802.1Qbb, CEE and CIN versions of PFC TLV are supported. DCBx also validates PFC
configurations 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 to be
noticed on the ingress ports for each removal or attachment of the policy. This behavior occurs because the
port is brought down when PFC is configured. When a DCB input policy with PFC profile is configured or
unconfigured on an interface or a range of interfaces not receiving any traffic, interfaces with PFC settings
that receive appropriate PFC-enabled traffic (unicast, mixed-frame-size traffic) display incremental values in
Control.
Data Center Bridging (DCB) 303