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TRENDnet User’s Guide
Industrial Managed Switch Series
31
Port Settings

Duplex mode
A duplex communication system is a system composed of two connected parties or
devices that can communicate with one another in both directions.
Half Duplex:
A half-duplex system provides for communication in both directions, but only one
direction at a time (not simultaneously). Typically, once a party begins receiving a signal,
it must wait for the transmitter to stop transmitting, before replying.
Full Duplex:
A full-duplex, or sometimes double-duplex system, allows communication in both
directions, and, unlike half-duplex, allows this to happen simultaneously. Land-line
telephone networks are full-duplex, since they allow both callers to speak and be heard
at the same time.

Loopback Test
A loopback test is a test in which a signal in sent from a communications device and
returned (looped back) to it as a way to determine whether the device is working right or
as a way to pin down a failing node in a network. One type of loopback test is performed
using a special plug, called a wrap plug that is inserted in a port on a communications
device. The effect of a wrap plug is to cause transmitted (output) data to be returned as
received (input) data, simulating a complete communications circuit using a single
computer.

Auto MDI-MDIX
Auto-MDIX (automatic medium-dependent interface crossover) is a computer
networking technology that automatically detects the required cable connection type
(straight-through or crossover) and configures the connection appropriately, thereby
removing the need for crossover cables to interconnect switches or connecting PCs peer-
to-peer. When it is enabled, either type of cable can be used or the interface
automatically corrects any incorrect cabling. For Auto-MDIX to operate correctly, the
speed on the interface and duplex setting must be set to "auto". Auto-MDIX was
developed by HP engineers Dan Dove and Bruce Melvin.

Auto Negotiation
Auto (auto-negotiation) allows one port to negotiate with a peer port automatically to
obtain the connection speed and duplex mode that both ends support. When auto-
negotiation is turned on, a port on the Switch negotiates with the peer automatically to
determine the connection speed and duplex mode.
If the peer port does not support auto-negotiation or turns off this feature, the Switch
determines the connection speed by detecting the signal on the cable and using half
duplex mode. When the Switch’s auto-negotiation is turned off, a port uses the pre-
configured speed and duplex mode when making a connection, thus requiring you to
make sure that the settings of the peer port are the same in order to connect.

Flow Control
A concentration of traffic on a port decreases port bandwidth and overflows buffer
memory causing packet discards and frame losses.IEEE802.3x flow control is used in full
duplex mode to send a pause signal to the sending port, causing it to temporarily stop
sending signals when the receiving port memory buffers fill and resend later.