Global Configuration - Lenovo RackSwitch G8264CS Application Manual

Global Configuration

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PFC requires CEE to be turned on ("Turning CEE On or Off" on page
CEE is turned on, standard flow control is disabled on all ports, and PFC is enabled
on all ports for 802.1p priority value 3. While CEE is turned on, PFC cannot be
disabled for priority value 3. This default is chosen because priority value 3 is
commonly used to identify FCoE traffic in a CEE environment and must be
guaranteed lossless behavior. PFC is disabled for all other priority values by
default, but can be enabled for one additional priority value.
 Global PFC configuration is preferable in networks that implement end‐to‐end
CEE devices. For example, if all ports are involved with FCoE and can use the
same SAN and LAN priority value configuration with the same PFC settings,
global configuration is easy and efficient.
 Global PFC configuration can also be used in some mixed environments where
traffic with PFC‐enabled priority values occurs only on ports connected to CEE
devices, and not on any ports connected to non‐CEE devices. In such cases, PFC
can be configured globally on specific priority values even though not all ports
make use them.
 PFC is not restricted to CEE and FCoE networks. In any LAN where traffic is
separated into different priorities, PFC can be enabled on priority values for
loss‐sensitive traffic.
 If you want to enable PFC on a priority, do one of the following:
Create a separate PG (separate COS Q) (or)

Move the priority to the existing PG in which PFC is turned on.

Option 1 will be more preferred as you have separate Q and separate ETS
configuration.
 When configuring ETS and PFC on the switch, perform ETS configuration
before performing PFC configuration.
 If two priorities are enabled on a port, the switch sends PFC frames for both
priorities, even if only traffic tagged with one of the priorities is being received
on that port.
Note: When using global PFC configuration in conjunction with the ETS feature
(see "Enhanced Transmission Selection" on page
pause‐tolerant traffic (such as lossless FCoE traffic) is assigned priority values
where PFC is enabled. Pausing other types of traffic can have adverse effects on
LAN applications that expect uninterrupted traffic flow and tolerate dropping
packets during congestion.
302). When
313), ensure that only
Chapter 17: FCoE and CEE
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