Dell Emulex Family of Adapters - Manual (Page 642)

Emulex Drivers for Windows User Manual P010077-01A Rev. A
3. Configuration
NIC Driver Configuration
642
L2 Flow Control
While running a port in generic pause mode because of congestion, RoCE latencies can
be adversely affected. Under these conditions, it is advisable to configure RoCE to use
PFC. PFC mode ensures that RoCE traffic latencies are unaffected in presence of
congestion as a result of NIC traffic. However, PFC mode is not required. For switches
and adapters that do not support PFC, RoCE can continue to work without PFC mode.
While you can still perform bandwidth allocation for RoCE traffic as opposed to NIC
traffic, this allocation cannot be guaranteed as all the outgoing traffic is paused.
Configuring QoS for RoCE
When configuring QoS for RoCE, it is important to keep in mind the following:

A limited QoS configuration is available through OneCommand Manager.

A single traffic class group for RoCE exists per port.

A single RoCE priority exists in PFC mode.

Bandwidth allocation for priority groups is supported.
Notes:

The Windows NIC driver does not support the Microsoft DCB/QoS API.

Powershell commands cannot be used to configure QoS-related parameters for
the RoCE profile.
RoCE Adapter Side
With DCBX enabled, the switch settings will be used for PFC. Ensure that the switch
settings used match the adapter default Priority 5 used for RoCE and PFC.
Note: PFC is enabled by default in OCe14000-series adapters.
Switch Side
For information on switch-side configurations, see appendix E., “RoCE Switch
Support,” on page 738.
OCe14000-Series Adapter Defaults
When using the OCe14000-series adapters for RoCE functionality, the following
defaults apply:

Adapter boot time

PFC is disabled on all the ports in the NIC+RoCE profile.

Generic Pause is enabled on all the ports in the NIC+RoCE profile.

Back to back connection (OCe14000 - OCe14000)

PFC is disabled by default.

Generic Pause is enabled on the connected port.

DCBX-enabled switch connection

When an OCe14000-series adapter is connected to DCBX-enabled switch, it
shifts the mode from Generic Pause to PFC.