Allied Telesis AT-S63 - Manual (Page 113)

AT-S63 Management Software Menus Interface User’s Guide
Section I: Basic Features 113
Configuring Flow Control and Back Pressure
A switch port uses flow control to control the flow of ingress packets
from its end node. Flow control applies only to ports operating in full-
duplex mode.
A port using flow control issues a special frame, referred to as a PAUSE
frame, as specified in the IEEE 802.3x standard, to stop the transmission
of data from an end node. When a port needs to stop an end node from
transmitting data, it issues this frame. The frame instructs the end node
to cease transmission. The port continues to issue PAUSE frames until it
is again ready to receive data from the end node.
The default setting for flow control on a switch port is disabled.
Back pressure performs much the same function as flow control. Both
are used by a port to control the flow of ingress packets. Flow control
applies to ports operating in full-duplex; back pressure applies to ports
operating in half-duplex mode.
When a twisted pair port on the switch operating in half-duplex mode
needs to stop an end node from transmitting data, it forces a collision. A
collision on an Ethernet network occurs when two end nodes attempt to
transmit data using the same data link at the same time. A collision
causes the end nodes to stop sending data.
When a switch port needs to stop a half-duplex end node from
transmitting data, it forces a collision on the data link, which stops the
end node. After the switch is ready to receive data again, the switch
stops forcing collisions. This is called back pressure.
The default setting for back pressure on a switch port is disabled.
To set up flow control or back pressure, perform the following
procedure:
1. From the Main Menu, type 1 to select Port Configuration.
The Port Configuration menu is shown in Figure 26 on page 106.
2. From the Port Configuration menu, type 1 to select Port
Configuration.
The following prompt is displayed:
Enter port-list ->