Which WAN carrier uses 23 B channels and one D channel?

The correct answer is ISDN-PRI, which stands for Integrated Services Digital Network - Primary Rate Interface. This technology is designed to provide a standard way for connecting telecommunication networks. It consists of 23 B (Bearer) channels and one D (Delta) channel.

The B channels are used for carrying voice and data, allowing multiple simultaneous connections, while the D channel is utilized for signaling and control purposes. This configuration makes ISDN-PRI particularly effective for businesses that require multiple phone lines and data connections over a single interface, enhancing both efficiency and capacity in communication.

Understanding ISDN-PRI in the context of WAN technologies is important, as it distinguishes itself by offering dedicated bandwidth and robust support for both voice and data. Other options like Frame Relay and SDSL serve different purposes and configurations that do not include this specific ratio of B to D channels, while T1 lines typically provide a dedicated circuit with a different structure, primarily focusing on data transmission rather than the specific combination of channels that ISDN-PRI offers.