Emulated Lan Components; Lan Emulation Client; Lan Emulation Server - 3Com CoreBuilder 9000 User Manual

376 C 15: LAN E
HAPTER
Emulated LAN
Components

LAN Emulation Client

LAN Emulation Server

MULATION
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 an LE Configuration Server (LECS), an LE Server (LES), and a
Broadcast and Unknown Server (BUS).
Each LEC is incorporated in an ATM edge device, such as a SuperStack
Switch 2700 or 7X00 Interface Card, 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 that 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 that joins an ELAN may
use the ELAN name in the configuration phase or join phase.
The LAN Emulation Server (LES) coordinates and controls an Emulated
LAN. It provides the central "directory" service of an emulated LAN to
which a LEC can turn to look up the ATM address of another LEC. The
LES directory contains a table of LAN destinations. LAN destination refers
to either a MAC address or a Route Descriptor, together with the ATM
addresses of the LECs that represent them. To transmit a data frame to a
particular LAN destination, the LEC sends the data frame to the LEC that
represents that LAN destination. If the LEC does not already know the
destination LEC's address, it can send the LAN destination to the LES to
look it up (resolve). To populate the LES directory, the LECs may register
the LAN destination of LAN stations they represent with the LES. Every
Route Descriptor must be registered with the LES.
The LE Service normally resides on a central ATM switch, such as the
CoreBuilder ® 9000 ATM Enterprise Switch, but may reside on an ATM
end station instead.
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