7
•
With Rx flow mode generic control enabled, an interface can receive flow control frames, but it
cannot send flow control frames. When the interface receives a flow control frame from its peer, it
suspends sending packets to the peer. When congestion occurs, the interface cannot send flow
control frames to the peer.
To handle unidirectional traffic congestion on a link, configure the
flow-control receive enable
command
at one end and the
flow-control
command at the other end. To enable both ends of a link to handle traffic
congestion, configure the
flow-control
command at both ends.
To enable generic flow control on an Ethernet interface:
Step Command
Remarks
1.
Enter system view.
system-view
N/A
2.
Enter Ethernet interface
view.
interface
interface-type
interface-number
N/A
3.
Enable generic flow control.
•
Enable TxRx mode generic
flow control:
flow-control
•
Enable Rx mode generic flow
control:
flow-control receive enable
By default, generic flow control is
disabled on an Ethernet interface.
Configuring PFC on an Ethernet interface
PFC performs flow control based on 802.1p priorities. With PFC enabled, an interface requires its peer
to suspend sending packets with certain 802.1p priorities when congestion occurs. By decreasing the
transmission rate, PFC helps avoid packet loss.
You can enable PFC for certain 802.1p priorities at the two ends of a link. When network congestion
occurs, the local device checks the PFC status for the 802.1p priority carried in each arriving packet. The
device processes the packet depending on the PFC status as follows:
•
If PFC is enabled for the 802.1p priority, the local device accepts the packet and sends a PFC pause
frame to the peer. The peer stops sending packets carrying this 802.1p priority for an interval as
specified in the PFC pause frame. This process is repeated until the congestion is removed.
•
If PFC is disabled for the 802.1p priority, the local port drops the packet.
To configure PFC on an Ethernet interface:
Step Command
Remarks
1.
Enter system view.
system-view
N/A
2.
Enter Ethernet interface view.
interface
interface-type
interface-number
N/A
3.
Enable PFC on the interface
through automatic negotiation
or forcibly.
priority-flow-control
{
auto
|
enable
}
By default, PFC is disabled.
4.
Enable PFC for specific
802.1p priorities.
priority-flow-control no-drop
dot1p
dot1p-list
By default, PFC is disabled for all
802.1p priorities.