Allied Telesis AT-MC303 - Manual (Page 15)

AT-MC300 Series Installation Guide
5
Note
The MissingLink feature is disabled when the MissingLink/Link Test
button is in the Link Test position.
Auto-negotiation Button
The AT-MC300 Series Media Converter can operate in either half- or full-
duplex mode. Duplex mode refers to the manner in which an end node sends
and receives data. An end node that is operating in half-duplex can either
send data or receive data, but not 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 in full-duplex,
since bandwidth is twice that compared to half-duplex.
The media converter is designed to determine the appropriate duplex port for
its ports through auto-negotiation. With auto-negotiation, the media converter
will determine the capabilities of the end nodes and will set the ports
accordingly. For instance, if the end nodes are capable of half-duplex mode
only, the unit will set its ports to half-duplex. It is important to note, however,
that both end nodes must operate with the same duplex mode. The network
will not function properly in situations where one end node is operating in
half-duplex and the other is operating in full-duplex.
The auto-negotiation feature on the media converter can be activated or
deactivated using the A/N button on the front panel. In nearly all situations,
you will want to leave the auto-negotiation capability activated on the
AT-MC300 Series Media Converter, so that the unit can determine the
appropriate duplex mode for the ports, based on the capabilities of the end
nodes. For example, auto-negotiation on the media converter should be left
activated in situations where both end nodes are also capable of auto-
negotiation, or where both end nodes have been pre-set to the same mode, or
are capable of operating in only one duplex mode, such as half-duplex.
There is, however, one situation where it might be necessary for you to disable
auto-negotiation on the unit, and that is to prevent a mismatch from occurring
between the duplex modes of the end nodes. This can occur where one end
node is capable of only half-duplex mode while the other end node will auto-
negotiate the duplex mode. For example, Figure 3 illustrates a media
converter that is interconnecting a 100Base-TX Ethernet hub capable of only
half-duplex operation and a 100Base-TX Ethernet switch that can auto-
negotiate the duplex mode.