In the reverse direction, Internet traffic for PCs connected to the IAD arrives at the IAD as ATM cells and is converted by the IAD into Ethernet. For telephony services, an ATM virtual circuit is provisioned between the IAD and the Voice Gateway. The Voice Gateway then converts the voice from ATM cells back into a TDM format that can be understood by the Class 5 switch. With ATM QoS, voice traffic is prioritized over data traffic in such a way that that voice traffic can be transmitted with minimal delay and jitter. In the traditional VoDSL network, GR-303 is used to obtain a transparent pipe between the Class 5 switch and the phone, and there just happens to be a VoDSL network in between the two.
Carriers can realize significant savings on a variety of fronts when they deploy a VoDSL network.
One network, not two. With VoDSL, carriers can realize significant capital and operational cost savings because they have to purchase and operate only one network, not two. Reduced access line costs. In the past, to deliver high-speed Internet access a dedicated T1 circuit would have to run to the customer premises. Another T1 circuit would have to be run to the customer premises for voice services.