Ref: 99980077
Title: Interconnecting Ethernet/Fiber-Optic Links
Date: 12/1/86

Copyright 3Com Corporation, 1991.  All rights reserved.

This article describes the use of repeaters and bridges to form
an extended Fiber-Optic Ethernet network.  The architectures for
linking networks can be divided into three types: connecting
networks via Inter-Repeater Links, connecting networks via
repeater and bridge, and connecting networks via two bridges.

The following sections describe in more detail the architecture
of each application.

.h1;Connecting Networks via Inter-Repeater Links - Remote
Repeater Application

Fiber-Optic Inter-Repeater Links are used to interconnect two
coaxial Ethernet segments.  This type of simple remote repeater
application is used mainly to extend the distance of two Ethernet
segments up to 2 Km.

This application consists of two Inter-Repeaters that attach to
the Ethernet networks via IEEE 802.3 transceivers and transceiver
cables and to the fiber-optic cable via SMA connectors.

The maximum distance between the two Inter-Repeaters links is 2
Km.  In this type of application, the standard Ethernet
limitation of four repeaters to form an extended network is
applied.  In other words, since these two networks are
interconnected via two Inter-Repeaters, the Ethernet network on
each side can only be extended to another link (via one
repeater).

The Bridge Communications Inter-Repeater supports 100/140 micron
fiber.  However, it can be special ordered to operate with 50/
125, 62.5/125 or 85/125 micron fiber.  In addition, the Inter-
Repeater has such functions as preamble reconstitution, fragment
extension, data retiming, and auto-partitioning of faulty
segments; the fiber-optic functions include loopback of data,
jabber protection, 100 percent reliable collision detection, idle
signal modulation, and light loss detection and indication.  The
front panel LEDs indicate partitioning of port 1 and port 2,
packet on either port, and DC power available.

.h1;Connecting Networks via Repeater and Bridge - Remote Bridge
Application

This section describes the use of a repeater and bridge to form a
fiber-optic Ethernet network.  This application combines two
physical networks to form a logical network.  With the presence
of the IB/2, this configuration performs local traffic filtering
and other complicated network management functions.  Moreover, it
allows the addition of more repeaters on each segment.

For example, two networks are interconnected via a Fiber-to-
Coaxial Repeater and Bridge Communications Internetwork Bridge/2
(IB/2).  Therefore, the local and remote sides can be extended to
five links via four repeaters.  The Bridge Communications Fiber-
to-Coaxial Repeater supports 100/140 micron fiber.  It can also
be special ordered with 50/125, 62.5/125, or 85/125 micron fiber.

.h1;Connecting Networks via Two Bridges

This section describes the use of bridges to form fiber-optic
Ethernet network.  With the presence of two IB/2s, this
application allows devices to communicate between two networks
regardless of protocol incompatibility (XNS, TCP, or DECNet).  In
addition, network management commands are available to simplify
the network management tasks.  Another advantage of this
application is that the distance between two networks can be
extended to 4 Km.

For example, two Bridge Communications IB/2s are used between two
networks.  These bridges are attached to the Ethernet Coaxial
Cable via IEEE 802.3 transceivers and transceiver cables and to
the fiber-optic cable via fiber-optic transceivers and transeiver
cables.


