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5.4.
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 direction
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.