Dell S6000-ON, Configuration Manual

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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 a
dash; 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 to
be 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 the
system. In other words, lossless queue limit is applicable on a per-port level and not on the global-config
context. For example, one of the Te/Fo interfaces can have pfc-dot1p priorities as 2 and 3. Whereas, the
other 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 particular
PFC-enabled traffic-flow to obtain lossless behavior.
Configuring PFC in a DCB Map
An 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. This
functionality is supported on the S6000–ON platform.
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 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 Control .
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
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Data Center Bridging (DCB)