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Chapter 1 Overview
Avaya M770 M-ACCF/SF ATM Access Modules User’s Guide 3
Network Layer Concepts — LAN Emulation
The following Sections describe the LAN emulation and ATM adaptation concepts
behind the network layer architecture of a typical ATM network.
Chapter 2 describes how to plan your ATM network and provides some examples
of where to use the ATM access module within an ATM network.
LAN Emulation Overview
LAN Emulation (LANE) is a method of connecting LAN users over an ATM network
which enables them to communicate with each other as if they were operating over
traditional LANs. LANE can be configured in an ATM network in several ways:
• To connect legacy end stations directly to other legacy systems, as well as to
servers, routers, switches and other networking devices attached to the ATM
network.
• To connect bridged-LAN environments to each other over ATM. In this case the
Emulated LAN acts as a bridge on the ATM network.
• To connect ATM end stations to each other, enabling communication between
them.
More than one emulated LAN can operate on the same ATM network. However,
each of the emulated LANs is independent of the others and users cannot
communicate directly across emulated LAN boundaries.
Emulated LAN Components
LAN Emulation is implemented as a set of connection services collectively called an
emulated LAN (ELAN). Each ELAN is composed of a set of LAN Emulation Clients
(LEC) and a single LAN Emulation Service. The latter consists of a LAN Emulation
Configuration Server (LECS), a LAN Emulation Server (LES), and a Broadcast and
Unknown Server (BUS).
LAN Emulation Client (LEC)
Each LEC is incorporated in an ATM edge device, such as the M-ACC module and
represents a set of the device’s LAN users to the ATM network. A LEC has a unique
LEC ID as well as an ATM address by which it is known in the emulated LAN. It
handles the forwarding of its LAN users’ data frames over the ATM network to
their destination, a task which also includes ascertaining the destination LEC
address and setting up the connection between them.
Also provided is a MAC-level emulated Ethernet service interface to higher level
software which implements the LAN Emulation User to Network Interface (LUNI).
An ELAN is assigned a name (ELAN name). A LEC joining an ELAN may use the
ELAN name in the configuration or join phase.