he key to success for large-scale IP networking lies in delivering the flexibility of IP routing with a switched packet-forwarding mechanism that offers the highest pos- sible performance and maximum control: IP switching. IP Switching IP switching was designed to speed up increasingly choked net- works by replacing slower, more processing-intensive routers with switches. IP routers that provide connection-oriented services at the IP layer are referred to as IP switches. Routers are slower than switches because they must examine multiple packet fields, make substitutions in the packet headers, and compute routes on a packet-by-packet basis, which introduces latency and congestion. The idea with IP switching is to make a connectionless data technology behave similar to a circuit-switched network. An IP switch routes the first packet, and then it switches all subsequent packets. The goal is to make intranet and Internet access faster and to enable the deployment of new voice, video, and graphics applications and services. Therefore, IP switching has two objectives: to provide a way for inter- networks to scale economically and to provide effective QoS support for IP. In Packet-Switched Networks essence, IP switching replaces Layer 3 hops with Layer 2 switching, which leads to good hardware-based forwarding performance. Even with the advantages of IP switching, IP still doesn't allow us to properly administer all the QoS parameters that are part of traffic definitions, and this is where ATM comes in. Features of ATM As discussed earlier in this chapter, ATM was created in the WAN environment. It came out of the carrier community as a means by which to reengineer the PSTN for multimedia and real-time streaming applications. Because ATM comes from the carrier environment, where traffic engineering is essential, it is a connection- oriented technique. It provides a means to establish a predefined path between the source and the destination, which enables greater control of network resources. Overallocation of bandwidth