D-Link DFE-680TXD - Manual (Page 5)

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best baud rate, compression method, and error correction method. When the two modems
have tested the phone-line quality and have switched to the combination of parameters
which will provide the best data communication, then you are given the “ connect”
message which signals the end of the inter-modem negotiation and the beginning of your
intended communication with the remote computer.
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-680TXD 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-680TXD 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
auto-negotiation between the DFE-680TXD and its supporting device begins and
proceeds automatically.
If the supporting switch or hub has autonegotiation functionality, then it and the DFE-
680TXD exchange a series of messages in which 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 devices.
If the supporting device does not have autonegotiation functionality, then its monotone
(single capability) message will be recognized by the DFE-680TXD’s autonegotiation
facility, and the DFE-680TXD will simply switch to the one of its own capabilities which
matches that of the supporting device.
Once the auto- negotiation is completed, then the line is ready, and it will provide an
optimal data channel between the DFE-680TXD and the supporting device. The line will
remain ready without further auto-negotiation action until the linkage is broken. Auto-
negotiation then reoccurs at any time that the linkage is restored, again making the line
ready for optimal data communications.