LAN emulation (LANE) is one method used to extend broadcast domains across an ATM wide-area network (WAN), regardless of the upper-layer protocols in use. LANE extends VLANs (virtual LANs) through the ATM WAN cloud in what is known as an Emulated LAN (ELAN).
ATM LANs do not operate in the traditional way that other LAN implementations do, where a LAN host sends data frames at any time to one or multiple hosts on the LAN. Hosts on an ATM LAN must initiate a call setup process prior to data transmission.
With this major difference among LAN architectures, the ATM Forum wanted to integrate ATM switches into the conventional LAN architecture. This solution is known as LAN emulation, or LANE.
LANE meets these ATM Forum requirements:
• LANE enables a set of systems that have ATM network interfaces (NICs) and are connected to ATM switches to emulate a traditional LAN environment.
• LANE enables Ethernet or Token Ring systems connected to traditional hubs and switches to interact with ATM implementations as if they all belong to a single conventional LAN.
• LANE also provides backward compatibility with existing higher-layer protocols and applications, making it possible for existing network implementations to run across an ATM implementation without making software changes. This implementation is possible because to the higher layers (OSI Layer 3, network layer, and above), the LAN environment appears to be Ethernet or Token Ring.
As of this writing, LANE does not support FDDI LAN implementations.
It is possible to build a high-performance LAN that spans multiple sites. Wide-area ATM can run at speeds that meet or exceed the bandwidth available by these local-area networks.
Figure 10-1 illustrates Ethernet LANs, interconnected by ATM switches across an ATM WAN. Also depicted are servers directly connected to each ATM switch.
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