Flow Control Using Ethernet Pause Frames - Dell PowerEdge M IO Aggregator Command Reference Manual

Flow Control Using Ethernet Pause Frames

An Aggregator auto-configures to operate in auto-DCB-enable mode (see
Auto-DCB-Enable
enhanced Ethernet (CEE) or not, and enable DCBX and PFC or link-level flow control accordingly:
• Interfaces come up with DCB disabled and link-level flow control enabled to control data transmission
between the Aggregator and other network devices.
When DCB is disabled on an interface, PFC, ETS, and DCBX are also disabled.
• When DCBX protocol packets are received, interfaces automatically enable DCB and disable
link-level flow control.
DCB is required for PFC, ETS, DCBX, and FCoE initialization protocol (FIP) snooping to operate.
Link-level flow control uses Ethernet pause frames to signal the other end of the connection to pause data
transmission for a certain amount of time as specified in the frame. Ethernet pause frames allow for a
temporary stop in data transmission. A situation may arise where a sending device may transmit data faster
than a destination device can accept it. The destination sends a pause frame back to the source, stopping the
sender's transmission for a period of time.
The globally assigned 48-bit Multicast address 01-80-C2-00-00-01 is used to send and receive pause
frames. To allow full duplex flow control, stations implementing the pause operation instruct the MAC to
enable reception of frames with a destination address equal to this multicast address.
The pause frame is defined by IEEE 802.3x and uses MAC Control frames to carry the pause commands.
Ethernet pause frames are supported on full duplex only. The only configuration applicable to half duplex
ports is rx off tx off
Note that if a port is over-subscribed, Ethernet Pause Frame flow control does not ensure no loss behavior.
The following error message appears when trying to enable flow control when half duplex is already
configured:
Can't configure flowcontrol when half duplex is configure, config ignored.
The following error message appears when trying to enable half duplex and flow control configuration is
on:
Can't configure half duplex when flowcontrol is on, config ignored.
140 | Interfaces
Mode). In this mode, Aggregator ports detect whether peer devices support converged
.
Data Center Bridging: