 edge is a key element of the next-generation infrastructure. Service providers face the challenge of supporting their existing data services while transitioning to a new IP world. They need a service edge platform that will allow them to achieve this goal. Multiservice switches can now support Layer 3 services while continuing to support traditional Layer 2 ATM and Frame Relay services, DSL aggregation, and voice and wireless applications. They also support Packet over SDH/SONET (PoS) and Ethernet interfaces, as well as interfaces for Frame Relay, ATM, Circuit Emula- tion Service, and TDM. IP, ATM, or IP, ATM, or MPLS Optical Backbone Frame Frame Relay Relay Figure 10.9 The network core serving the edges The Next-Generation Network Infrastructure Most of today's Tier 1 service providers have ATM-based networks that support Frame Relay, ATM, and private-line services. These services continue to show growth. For example, IP traffic growth in the United States is expected to be approx- imately 75%, while non-IP data is expected to grow at approximately 40%. Service providers are looking for new IP and Ethernet revenue streams while continuing to support and grow their current private-line, Frame Relay, and ATM services. How- ever, service providers don't know how the service mix will change over time and therefore need the flexibility to manage changing demand. An additional complication comes from the fact that while non-IP data repre- sents a decreasing percentage of traffic, the revenues associated with these services remain significantly higher than those for IP. Revenues for IP are expected to be only 5% of total Frame Relay and ATM revenues. (But bear in mind that customers are used to paying more for Frame Relay and ATM data services, and of course the service providers are more than happy to maintain the status quo.) The trend is to accommodate a full mix of services. Service providers will use a combination of Layer 2 and Layer 3 networks to deliver new services, and the choice will depend on many variable