D-Link DFE-690TXD User Manual - About Autonegotiation

5 

About Autonegotiation 

The basic idea of auto-negotiation can be understood by reflecting for a 

moment on the familiar process of making a dialup connection between 

two modems. You have probably heard some exchanges between your 

local modem and a modem at the other end of a telephone line. (These 

exchanges are ordinarily played out through a speaker in your local 

modem). As irritating 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. 

The preparatory work of the two modems during those few seconds 

before you see the “connect” message is to negotiate the best data 

communication scheme which is supported by both modems, and which 

is suitable for the quality of the telephone-line connection between them. 

The parameters to be settled between the two modems include 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