the local loop, ATM may be a valuable solution for the against the current generation of TDM solutions that are carriage of voice and data to business premises. successfully deployed. ATM Forum's VTOA workgroup, Alternate Carriers or Value-Added Network Suppliers which is actively involved in developing standards take up licenses to provide communication services in for VoATM networks, has developed a set of solutions or competition with the incumbent national operators. In- standards that could offer direct commercial stead of having their own transmission infrastructure, or operational benefits to any user. These standards they buy bandwidth from the primary operator. Cost and allow voice traffic to be carried over an ATM net- limited availability of bandwidth demand ATM efficiency work more efficiently than any packet- or TDM-based as well as the integration of voice and data services. An infrastructures. example of alternate carriers is cellular phone operators. The ATM Forum has defined three principal appro- Private/Enterprise networks buy bandwidth at com- aches to carrying voice over an ATM network. These are mercial (retail) rates and achieve the most they can with Circuit emulation services (CES), which are used to the resources on hand. Such organizations will have al- carry full or fractional E1/T1 circuits between end ready deployed a TDM network utilizing E1 or T1 links. points. They will be looking to integrate these solutions into a new ATM network and gain improvements in network performance and efficiency by moving from TDM to Table 3.2-3 Objectives to be achieved-1. statistical multiplexing. With this scenario, two voice transport models have come up. One is known as "voice Characteristics Necessity trunking" and the other as "voice switching." Adaptation A mechanism to encode voice samples into ATM while meeting the delay and a) Voice trunking real-time constraints of voice traffic This involves tunneling of voice traffic over the ATM Signaling A mechanism that allows the network between two f