Allied Telesis AT-MC1001SC/GS4 - Manual (Page 16)

6
Link Test Standalone/Back to Back Button
The Link Test Standalone/Back to Back button (see Figure 2) is used together
with the Link Test/MissingLink switch. When performing a link test on the
media converter, use this switch to configure the unit to match the topology in
which you installed the media converter. The two possible network topologies
for the media converter, standalone and back to back, are described in the
section “Network Topologies” on page 8. This button must be set correctly in
order for a link test to be performed accurately. To perform a link test, refer to
“Testing and Troubleshooting the Media Converter” on page 15.
Caution
The media converter will not pass network traffic when a link test is
being performed, thus possibly disrupting network operation. Only when
the Link Test switch is in the M/L ON (DOWN) position will the media
converter pass network traffic.
Half- and Full-Duplex Mode
Duplex mode refers to the way a node sends and receives data on the network.
A node can operate in either half- or full-duplex mode, depending on its
capabilities. A node that is operating in half-duplex mode can either send data
or receive data, but it cannot do both at the same time. A node that is
operating in full-duplex mode can send and receive data simultaneously. The
best network performance is achieved when a node can operate at full-duplex,
since the node is able to both send and receive data simultaneously.
The media converter is transparent to the duplex mode of the nodes that are
connected to its two ports. That is, the media converter can operate with nodes
operating at either half-duplex or full-duplex mode. However, it is important
to remember that the two nodes connected to the ports on the unit must
operate with the same duplex mode.
For example, assume that the 1000Base-SX port on the media converter is
connected to a port on an Ethernet switch configured for half-duplex
operation, while the 1000Base-LX port is connected to a port on another
Ethernet switch configured for full-duplex operation. This would be an invalid
configuration and could adversely impact the performance of the network.
Either the port on the Ethernet switch connected to the 1000Base-SX port
would have to be changed to full-duplex (if it supports that capability), or the
Ethernet switch port connected to the 1000Base-LX port would need to be
changed to half-duplex.