Allied-telesis AT-MC103ST/FS3, FS4 Manual de usuario descargar pdf (Pagina 15)

AT-MC100 Series Installation Guide

Auto-negotiation Button

The auto-negotiation button, located on the front panel, disables the auto-

negotiation feature (IEEE 802.3u) of the media converter. The media

converter uses auto-negotiation to determine the duplex mode of the ports.

The duplex mode refers to the manner in which a node sends and receives

data on the network. Depending on its capabilities, a node can operate in

either half- or full-duplex mode. A node operating in half-duplex can either

send or receive data, but not both at the same time. However, a node

operating in full-duplex can send and receive data simultaneously. The best

network performance is achieved when a node can operate in full-duplex

mode.

In most configurations, you will want to leave the auto-negotiation button

activated so the unit can determine the appropriate duplex mode, based on the

capabilities of the end nodes. For example, the auto-negotiation feature on the

media converter should be left activated in situations where both end nodes

are also capable of auto-negotiation, or where both end nodes have been pre-

set to the same mode or are capable of operating in only one duplex mode, such

as half-duplex.

There is one situation where it may be necessary to disable the auto-

negotiation feature, and that is to prevent a mismatch from occurring between

the duplex modes of the end nodes. For example, Figure 2 shows two units

that have been connected with a media converter. Unit 1 is a repeater that is

capable of operating in half-duplex mode only. Unit 2 is a switch that can

operate in either half- or full-duplex mode, and will auto-negotiation the

duplex mode.

In attempting to auto-negotiate with Unit 1, the media converter will

determine that the unit is capable of half-duplex only and will set the port

connected to the unit appropriately. In auto-negotiating with Unit 2, the

media converter will determine that the unit can manage full-duplex and will

set the port connected to the unit to full-duplex. The result is a mismatch,

with one unit operating in half-duplex and the other unit operating in

full-duplex. This is referred to as a classic duplex mode mismatch and will

result in poor network performance between the end nodes.

Figure 2

Example of a Duplex Mode Mismatch

TX RX

MC103SC/FS3 FAST ETHERNET MEDIA CONVERTER

M/L

LNK TST

CLASS 1

LASER PRODUCT

DO NOT STARE

INTO BEAM

100Base-FX 100Base-TX

SINGLE MODE

FDX

LNK

ACT M/L ON

PWR

LNK

ACT A/N OFF MDI-X

A/N ON MDI

Unit 1

Unit

100Base-TX Repeater

Media Converter 100Base-TX Switch

1 2 ... 10 11 12 13 14 15 16 17 18 19 20 ... 47 48

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