16.4. VoDSL Architectures

There are three basic architectures for DSL, each of which makes use of a different layer of the communications stack for carrying the voice-over DSL connection. Figure 16.7 illustrates these three basic architectures:

  1. Voice-over IP (VoIP) in which voice is encapsulated within IP data packets. In this case voice is transmitted at Layers 3 and 4 of the communications stack.

  2. Voice-over ATM in which the voice is encapsulated within ATM cells. In this case the voice traffic is transmitted at layer 2 of the communication stack.

  3. Channelized voice over DSL (CVoDSL), where the digitized voice is carried directly on the PHY of the DSL link.

Figure 16.7. VoDSL architecture on the communications stack.

16.4.1. VoIP and DSL

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