Cisco Systems RJ-45-to-AUX manual ATM-Easy to Learn?, 161

∙Scalability—ATM is highly flexible, accommodating a wide range of traffic types, traffic rates, and communications applications.

An ATM network includes two types of devices: ATM switches and ATM endpoints. One type of ATM interface, called a user−network interface (UNI), connects an ATM device to a switch; a second type, called a network−to−network interface (NNI), connects an ATM switch to another ATM switch.

ATM has built−in support for Quality of Service (QoS), which is used to guarantee a level of service for networks that use ATM. This guarantee includes bandwidth utilization and data throughput. This type of service is critical when dealing with newer multimedia technologies.

LANE

LANE is a method used to provide backward compatibility to legacy Ethernet and Token Ring networks. LANE makes an ATM interface look like an Ethernet or Token Ring network interface, so no modifications to existing network drivers or applications need to be made to support ATM environments. LANE allows ATM networks to emulate Media Access Control (MAC) broadcast networks. Before the implementation of LANE, a proprietary emulation device was needed to connect ATM to a LAN topology.

ATM LANE works with a client/server architecture to create an emulated LAN (ELAN). An ELAN is very similar to a VLAN, in that it limits local broadcasts and multicast traffic to the ELAN. LANE devices can be either clients or servers. The LANE Emulation service (LE service) consists of several different components:

∙LAN Emulation Client (LEC)—Resides in every ATM device and provides a LAN interface to higher layer protocols.

∙LAN Emulation Server (LES)—The centerpiece of the LANE architecture. A single LES is responsible for address registry and resolution for an ELAN.

∙Broadcast and Unknown Server (BUS)—The means by which ATM provides broadcasting support for an ELAN.

∙LAN Emulation Configuration Server (LECS)—Contains the database of LES/BUS pairs for all the configured ELANs.

LANE is discussed in much more detail later in this chapter.

ATM—Easy to Learn?

Nothing in ATM makes it easy to comprehend and learn. It defies a lot of what today’s network administrators have learned. Telling you that ATM is used as a backbone protocol in the network makes you think that you do not need to worry about packet−based broadcast LANs trying to communicate with cell−based ATM networks (which will be discussed in the following sections). In this chapter, I discuss how to connect ATM—which is a connection−oriented, point−to−point protocol—to the Layer 2 addresses of the broadcast domains in the LAN.

ATM is a difficult subject for most people, because they rarely are exposed to it on a day−to−day basis like Ethernet or Token Ring. In today’s networking environment, however, increased emphasis is being put on integrating data, voice, and video in networks, and ATM is a driving force. No other protocol today has ATM’s ability to ensure timely delivery of packets based on their type. In addition, ATM can be used on both LANs and WANs on almost any types of media, with speeds that can scale up to gigabits per second.

161