Allied Telesis AT-MC13 - Manual (Page 16)

Chapter 1: Overview
16
depending on its capabilities. An end-node that is operating in half-duplex
mode can either send data or receive data, but it cannot do both at the
same time. An end-node that is operating in full-duplex mode can send
and receive data simultaneously. The best network performance is
achieved when an end-node can operate at full-duplex, since the end-
node is able to send and receive data simultaneously.
The twisted pair port and fiber optic port on the media converter can
operate in half-duplex, full-duplex, or auto-negotiate the duplex mode.
The media converter sets the duplex mode automatically through auto-
negotiation. With auto-negotiation, if the end-node is capable of full-
duplex, the port is set automatically to full-duplex mode. If the end-node is
capable of half-duplex, the port is set automatically to half-duplex mode.
The AT-MC13 media converter can operate in full-duplex, half-duplex, or
auto-negotiate the duplex mode. However, the end-nodes connected to
the AT-MC13 media converter must operate in the same duplex mode to
avoid a duplex mode mismatch, which can result in poor network
performance.
Figure 3 shows an example of a duplex mode mismatch. A repeater (Unit
1), capable of operating in half-duplex mode only, is connected to the
10Base-FL port on the media converter, while a switch (Unit 2), capable
of either half- or full-duplex mode, is connected to the 10Base-T port on
the media converter.
Figure 3. Example of a Duplex Mode Mismatch
In attempting to auto-negotiate with Unit 1, the media converter will
determine that the repeater is capable of half-duplex only and will set the
port connected to the unit appropriately. In auto-negotiating with Unit 2,
the media converter will determine that the switch can manage full-duplex
and will set the port connected to the switch to full-duplex. The result is a
duplex mode mismatch, with one unit operating in half-duplex and the
other unit operating in full-duplex. You could resolve this duplex mode
mismatch by manually configuring Unit 2, if possible, so that the port
connected to the media converter is set to half-duplex.
AT-MC13 ETHERNET MEDIA CONVERTER
NORMAL
LNK TST
10Base-FL 10Base-T TX RX
MDI MDI-X
PWR
NORMAL
REC
LINK
REC
LINK
CLASS 1 LED PRODUCT
1201
Unit 1 Unit 2
10/100Base-TX Repeater Media Converter 10/100Base-TX Switch