The enterprise IP-PBX market has moved well beyond the days of protracted testing in enterprise IT labs, and into substantial numbers of user deployments. While businesses are still not likely to upgrade their legacy systems to IP-based systems, nearly all new developments have some degree of IP components. More and more businesses are opting for more IP-centric solutions, and by 2006, it is expected that more than 90 percent of all new IP-PBX seats will be on all-IP systems, according to technology research firm ABI. One indication of the penetration of IP telephony is the extent to which businesses take advantage of IP in new phone system deployments. While the market for and interest in IP-PBX was active in 2001 and 2002, the majority of seats were IP-enabled. In these systems, a VoIP gateway was added to a legacy PBX system, allowing businesses to save cost on interoffice toll calls by routing them over a wide area network (WAN) rather than using the public telephone network and often providing access to some next-generation features. While growth is slowing to rates found in a more mature market, shipments of IP-PBXs are steadily increasing, as more businesses opt for VoIP systems instead of their circuit-switched counterparts. IP-PBX seat shipments are projected to grow from 3.2 million in 2003 to 26 million in 2009, according to findings by ABI.