Allied Telesis AT-MC16 - Manual (Page 16)

6
Auto-negotiation
Auto-negotiation determines the duplex mode of the ports. The duplex mode
refers to the manner in which an end-node sends and receives data on the
network. Depending on its capabilities, an end-node can operate in either half-
or full-duplex mode. An end-node operating in half-duplex can either send or
receive data, but not both at the same time. However, an end-node operating
in full-duplex can send and receive data simultaneously. The best network
performance is achieved when an end-node can operate in full-duplex mode.
The AT-MC13, AT-MC14, and AT-MC16 media converters can operate in
either full- or half-duplex mode. However, it is important to note that the end-
nodes connected to these media converters must operate in the same duplex
mode to avoid a duplex mode mismatch which can result in poor network
performance.
Figure 1 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-F
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 1 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 can resolve the duplex mode mismatch by
manually configuring Unit 2, if possible, so that the port connected to the
media converter is set to half-duplex.
Unit 1
Unit 2
100Base-TX Repeater Media Converter 100Base-TX Switch
REC
LNK
TX RX
MDI MDI-X
FIBER LINK TEST 10Base-T REC
LNK
PWR
NML
10Base-F