read and hear, especially as IP is the public's current darling. (Later in this chapter, the section "IP and ATM" discusses the possibility and benefits of marrying ATM and IP.) By definition, ATM is a high-bandwidth, fast packet-switching and multiplex- ing technique that enables the seamless end-to-end transmission of voice, data, image, and video traffic. It's a high-capacity, low-latency switching fabric that's adaptable for multiservice and multirate connections. The capacities it affords, including low latency, are absolutely prerequisite to supporting the advanced appli- cations for which this switching technology was designed. ATM switches characteristically have large capacities. They range from 10Gbps to 160Gbps, and there are new products in the Tbps range. (In comparison, IP routers typically offer capacities ranging from 4Gbps to 60Gbps, although there are also new Tbps switch routers.) The best advantages of ATM include the robust QoS and high-speed interfaces. ATM was the first networking approach to support high-speed interfaces, both 155Mbps and 622Mbps. Therefore, when an enterprise wanted to reengineer its campus network to higher bandwidth, ATM presented a viable solution. But the 1997 introduction of Gigabit Ethernet presented a more economical approach for obtaining high bandwidth, so today ATM is implemented in the enterprise because it offers the capability to administer QoS for multimedia and real-time traffic. Of course, over time, other solutions and architectures also begin to incorporate the features that people seek, SO new-generation IP routers and switches accommodate the same high-speed interfaces that ATM does. Both ATM and IP today ship with 2.5Gbps (i.e., OC-48) interfaces. Today, ATM can administer QoS, and IP is getting close. (QoS and ATM's service classes are discussed in detail in Chapter 10.) ATM enables access bandwidth to be shared among multiple sources, and it enables network resources to be shared among multiple users. It allows different services to be combined with