The LAN Emulation Module allows an ATM card to function in an Ethernet environment by making the ATM card appear to overlying Applications and protocols as if it were Ethernet. Emulation exposes Ethernet at the top, while allowing the card to function as ATM below. LAN Emulation works like a translator, working with the ATM card and the call manager to accept Ethernet headers and addresses, resolving the connectionless Ethernet world to the virtual-circuit requests of the ATM connection-oriented world.
The LAN Emulation module has both a client and a server component. Upon startup, all LAN Emulation clients on a network report to the LAN Emulation server, to get registered, and have their ATM addresses mapped to assigned Ethernet addresses.
At run time, the transport driver, such as TCP/IP, sends an Ethernet packet to a manufactured Ethernet address, which the LAN Emulation client maps to an ATM address to create a virtual circuit. The LAN Emulation server has a master database, or lookup table, specifying which Ethernet addresses map to which ATM addresses. An ATM address is returned to the client, which then makes a VC to that ATM address. In this way, the LAN Emulation client makes the world look like Ethernet above, while using actual ATM below.
LAN Emulation not only allows ATM networks to be used with connectionless LAN cards, but also allows communication through an ATM card, through a switch, onto a homogenous Ethernet network, a quality which is important for migration.