Allied Telesis AT-S63 - Manual (Page 109)

AT-S63 Management Software Menus Interface User’s Guide
Section I: Basic Operations 109
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 25 on page 102.
2. From the Port Configuration menu, type 1 to select Port Configuration.
The following prompt is displayed:
Enter port-list ->
3. Enter the number of the port you want to configure. To configure a
range of ports, enter the first and last ports of the range, separated by
a dash (for example, 4-8). You cannot specify nonconsecutive ports
(for example, 5,7,9)