cation-specific interapplication protocols. Application-Specific Call-Processing Protocols Application Application Platform Interapp Protocols Layer TAPI, JTAPI, etc. H.323, SIP, others Signaling Signaling Platform Signaling Protocols Media/Bearer Layer Control Protocols MGCP, TDM, Frame Relay, ATM Megaco Media Bearer Layer Platform Media Transport Figure 9.1 The IPT network taxonomy Between the bearer and signaling platforms are media/bearer control protocols. This is the realm of MGCP and Megaco. Between the signaling and application lay- ers are call-processing protocols such as Telephony Applications Programming Interface (TAPI) and Java TAPI (JTAPI). In terms of the transport infrastructure, a number of packet network alterna- tives can be used, and the full range of packet-switching techniques-including IP, Frame Relay, ATM, MPLS, and GMPLS, as well as Ethernet, Voice over Wireless LAN (VoWLAN), Voice over DSL (VoDSL), and Voice over Cable-can act as the transport infrastructure. Until recently, the IPT business model has been much like the traditional circuit- switched world, with each vendor supplying its own platform, handset, gateway, call-processing, and end-user feature sets. Convergence for the early IPT player involved converging voice onto the data network and selling telephony to the IT buyer. To this day, one of the greatest challenges is for traditional voice vendors to learn to sell what the data people buy. Many in the industry view long-distance as the first major market disruption in the transition from TDM to IP and handsets as the second. Initially, IPT had the most disruptive effect on carriers' transmission networks. This promoted a com- petitive triangle between the handset, the platform, and the network. Industry ana- lysts predict that the next few years will see battle between these three industries as each attempts to commoditize the other two. The IPT Network Architecture The first requirement for an IPT network is an IP local exchange or media gateway (also referred to as a VoIP g