ively, and greater processing power (following Moore's Law) applied to signal processing along with lower costs makes VoIP attractive. Second, as discussed later in this chapter, standards for VoIP have made progress. Third, IP has become pervasive: It is easier now for both businesses and consumers to enter the IPT realm. Finally, the marketplace is now home to many commercial entries. Moore's Law Moore's Law refers to a prediction made in 1965 by Gordon Moore, cofounder of Intel. Moore said that the number of transistors occupying a square inch of integrated circuit material had doubled each year since the invention of the integrated circuit, and he predicted that this multiplication of circuitry would continue. For the most part, the prediction held true until the late 1970s, when the time span of a year increased to about 18 months. Today Moore's Law is commonly used as an expression to state that the power of microprocessor technology doubles and its cost of production halves every 18 months. Many variations of phones, gateways, IP PBXs, and open-source PBXs are now available to both consumers and enterprises. Several key milestones have been reached. There has been a surge of Session Initiation Protocol (SIP) support and offerings for SIP-based enterprise communications, and SIP products are now widely available. Avaya (www.avaya.com), Lucent (www.lucent.com), and NEC (www.nec.com) have announced SIP enterprise product lines. Microsoft (www. microsoft.com), IBM (www.ibm.com), Novell (www.novell.com), and Sun Micro- systems (www.sun.com) are all moving to SIP for their enterprise collaboration tools. Cisco (www.cisco.com) has announced the migration of its proprietary call manager technology to SIP. (SIP is discussed in detail later in this chapter.) Most enterprises today are not using or considering IPT services, but many are using or considering migrating to Multiprotocol Label Switching (MPLS), in part because combining voice, video, and data can finally justify the cost of MPLS. Most organizations are c