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LAN emulation software is a layer of protocol software that operates between the data networking protocol and the ATM protocol. The software emulates existing LAN services, making the ATM network appear connectionless and allowing existing network protocols to run over ATM without modification.
An emulated LAN (ELAN) is logically analogous to an Ethernet/IEEE 802.3 or 802.5 segment. Multiple ELANs can be configured within an ATM network. LAN emulation also supports today's bridging and routing methods to allow interoperability between software applications residing on ATM-attached end systems and traditional LAN end systems.
Each ELAN consists of one or more LAN Emulation Clients (LECs) and a single LAN Emulation Service that resides in the ATM network or on the ATM switch. The LAN Emulation Service includes LAN Emulation Servers (LESs), Broadcast Unknown Servers (BUSs), and one optional LAN Emulation Configuration Server (LECS). These components are defined as follows:
An ELAN interfaces with a network protocol in the same way that a traditional LAN does. When a network protocol sends a packet, it sends the packet to the LEC and provides the MAC address of the LAN destination. The LEC, operating with the LES and BUS, determines the ATM-attached end station representing the LAN destination. The packet is then sent to this destination over the ATM network. Together, the LEC, LES, and BUS perform the following functions:
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