Voice over DSL
VoDSL combines asynchronous transfer mode (ATM) with DSL service to deliver voice and data
services over a single copper line. The different attributes of DSL technology and ATM functionality
work well together. DSL links are ideally suited for voice and data integration. ATM can
simultaneously carry voice and data traffic. VoDSL is usually provisioned as an overlay to a DSL
broadband access network. A VoDSL implementation requires several additional components.
A voice gateway resides at the service provider’s central office near a PSTN telephone switch
(Class 5 Switch) and serves as the bridge between the circuit-based voice switch and the packet-based
DSL network. An IAD, located at each customer premises, is connected to the DSL circuit. The device
manages voice services via analog POTS ports and Internet service through an Ethernet port. Existing
telephone and LAN equipment interconnect with the IAD.
The IAD converts LAN and voice data to ATM cells and transmits the data over the DSL link to
the service provider’s network. The DSL Access Multiplexer (DSLAM) aggregates traffic coming from
individual lines; encapsulated voice traffic is sent to the voice gateway and the data traffic is
carried as packet or cell to its final destination, an ISP or corporate network. The voice gateway
converts the voice traffic to conventional voice signals and sends it to a Class 5 voice switch.