DFE-660TX Fast Ethernet PC Card User's Guide
4
Introduction
Autonegotiation between devices within an Ethernet LAN is similar
in concept, but much briefer. The two devices involved in the
autonegotiation will be your DFE-660TX and the switch or hub
through which it is connected into the LAN. (Switches ordinarily
provide for autonegotiation; traditional hubs do not.) The
parameters to be negotiated between the DFE-660TX and its
supporting switch or hub include speed (100Mbps = Fast Ethernet,
or 10Mbps = traditional Ethernet) and duplex mode (half-duplex or
full-duplex).
Startup communication between the two devices occurs when both
devices are operating, the cable connection between them is good,
and the connected notebook PC's network software is loaded. As
soon as those conditions are satisfied, the preparatory process of
autonegotiation between the DFE-660TX and its supporting device
begins and proceeds automatically.
If the supporting switch or hub has autonegotiation functionality,
then it and the DFE-660TX exchange a series of messages in which
each device signals its capabilities and listens for corresponding
information about the other. The autonegotiation process requires
only a few milliseconds, and the two devices select the best
communication parameters supported by both devices.
If the supporting device does not have autonegotiation functionality,
then its monotone (single capability) message will be recognized by
the DFE-660TX’s autonegotiation facility, and the DFE-660TX will
simply switch to the one of its own capabilities which matches that
of the supporting device.
Once the autonegotiation is completed, then the line is ready, and it
will provide an optimal data channel between the DFE-660TX and
the supporting device. The line will remain ready without further
autonegotiation action until the linkage is broken. Autonegotiation
then reoccurs at any time that the linkage is restored, again making
the line ready for optimal data communications.
