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D-Link DFE-530TX+ User Manual
Appendix A - Technology Basics
About Auto-Negotiation
You have probably had the experience of making a dialup connection through a modem, and have heard the sound
exchange between your modem and the modem at the other end of the telephone line. As unpleasant as those few
seconds of noise may be, they do let you know that your modem and the remote modem are on the job, preparing for
your intended communication with the remote computer.
When the two modems have tested the phone-line quality and settled on the combination of shared options and
parameters which will provide the best data communication over the connecting phone line, then you are given
the “connect” message which signals the end of the intermodem negotiation and the beginning of your intended
communication with the remote computer.
Auto-negotiation between devices within an Ethernet Local Area Network (LAN) is similar in concept, but much briefer.
The two devices involved in the auto-negotiation will be the DFE-530TX+ Adapter serving your station (installed in
your computer), and the switch through which it is connected to the LAN. The options to be negotiated between the
DFE-530TX+ and its supporting switch includes Ethernet type (100BASE-TX Fast Ethernet or 10BASE-T Ethernet)
and duplex mode (half-duplex, being one-way-at-a-time, or full-duplex, being simultaneous transmit-and receive.)
Startup communication between the two devices occurs when both devices are powered up. Once the cable connection
and the Network Operating System software is satisfied, the preparatory process of auto-negotiation between the
DFE-530TX+ and its supporting switch proceeds automatically. If the switch has auto-negotiation functionality, it and
the DFE-530TX+ exchange a series of messages, each device signals its capabilities and listens for corresponding
information about the other. The auto-negotiation process requires only a few milliseconds, and the two devices select
the best communication parameters supported by both.
If the switch does not support auto-negotiation, the (single capability) message will be recognized by the DFE-530TX+
auto-negotiation facility, which will switch to those settings of its own capabilities, which match that of the switch.
Auto-negotiation reoccurs any time the linkage is restored, making the line ready again for optimal data
communications.
Summary of Contents for DFE-530TX+
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