IBM ATM OC-3c - Manual (Page 15)

What is LAN Emulation (LANE)? 2-3
LAN Emulation Components
Each Emulated LAN (ELAN) is composed of a set of
LAN Emulation components. This section describes
each of these components.
LAN Emulation Client (LEC)
Each ATM device has a number of LAN Emulation
clients. Each LAN Emulation Client (LEC) is responsible
for taking Ethernet frames and passing them through
the ATM network to the LEC serving the destination
address. The destination LEC is responsible for receiving
the frame from the ATM network and passing it to the
local Ethernet network, where it can be delivered to the
destination address.
LAN Emulation Server (LES)
Each LAN Emulation Server (LES) controls a single
Emulated LAN (ELAN). The purpose of the LES is to
store address and control information for the ELAN it
is serving, and to pass this information onto the
clients and other components within the ELAN.
The LES, therefore, needs to know the address of
every client and component in the ELAN.
Broadcast and Unknown Server (BUS)
Each ELAN has a Broadcast and Unknown Server (BUS).
The BUS forwards frames that it receives from any
client to all of the clients in the ELAN. The BUS is used
to forward broadcast and multicast frames so that they
are flooded throughout the ELAN. The BUS also floods
unicast frames if the location of the destination MAC
address is unknown.
LAN Emulation Configuration Server (LECS)
The LAN Emulation Configuration Server (LECS) is an
optional component, and is not essential for the
normal running of an ELAN.
The LECS stores the names of all the ELANs that have
been set up on the ATM network, and the address of
the LAN Emulation Server (LES) that serves each of
these ELANs.
If there is an LECS on the network, any client can
interrogate the LECS to find the address of the server
associated with the ELAN they wish to join. The
clients may also get ELAN configuration information
from the LECS.
If a LECS is not present on the ATM network, the server
address to be used by the client must be specified using
the management software on that client’s ATM device.