Ipsilon (now Nokia) pioneered IP Switching, a technique that combines layer 2 switching with layer 3 routing. An IP Switching device identifies a long flow of packets and switches the flow in layer 2 if possible, thus bypassing routers and improving throughput. IP Switching integrates fast ATM hardware directly with IP, thus preserving the connectionless nature of IP. Note that the term "IP switching" is often used to describe a variety of switch routing techniques. These other techniques are discussed under "IP over ATM."

IP Switching gained notoriety in the mid-1990s because its multilayer switching scheme bypassed traditional ATM signaling and addressing schemes, and replaced them with a scheme that integrated layer 2 and layer 3. Ipsilon's switch controller was basically a high-speed IP router that controlled an ATM switch.

IP switching is no longer an important technology. Label switching techniques are now considered more viable. See "Label Switching." You can refer to RFC 1953 (Ipsilon Flow Management Protocol Specification for IPv4, May 1996). Noritoshi Demizu's multilayer routing Web page provides information about all the switching and routing techniques available today.