Effects on flow control – Blade ICE RACKSWITCH G8124-E User Manual
Page 194
BLADEOS 6.5.2 Application Guide
194 Chapter 14: FCoE and CEE
BMD00220, October 2010
If the prior, non-CEE configuration used 802.1p priority values for different purposes, or does not
expect bandwidth allocation as shown in
, when CEE is turned on, the
administrator should reconfigure ETS settings as appropriate.
Each time CEE is turned on or off, the appropriate ETS or 802.1p QoS default settings shown in
are restored, and any manual settings made to prior ETS or 802.1p QoS
configurations are cleared.
It is recommended that a configuration backup be made prior to turning CEE on or off. Viewing the
configuration file will allow the administrator to manually re-create the equivalent configuration
under the new CEE mode, and will also allow for the recovery of the prior configuration if necessary.
Effects on Flow Control
When CEE is off (the default), 802.3x standard flow control is enabled on all switch ports by
default.
When CEE is turned on, standard flow control is disabled on all ports, and in its place, PFC (see
“Priority-Based Flow Control” on page 200
) is enabled on all ports for 802.1p 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.
Each time CEE is turned off, the prior 802.3x standard flow control settings will be restored
(including any previous changes from the defaults). However, each time CEE is turned on, the
default PFC settings are restored and any prior manual PFC configuration is cleared.
It is recommend that a configuration backup be made prior to turning CEE on or off. Viewing the
configuration file will allow the administrator to manually re-create the equivalent configuration
under the new CEE mode, and will also allow for the recovery of the prior configuration if necessary.
When CEE is on, PFC can be enabled only on priority value 3 and one other priority. If flow control
is required on additional priorities on any given port, consider using standard flow control on that
port, so that regardless of which priority traffic becomes congested, a flow control frame is
generated.