Real-time, or immediate, replication can be either synchronous (data is written to both storage devices at the same time, and the write operation isn't complete until both devices have completed writing) or asynchronous (data is written to both storage devices at once, although the write operation is considered complete when the primary storage device has completed writing).

TECHNOLOGIES Percentage of districts reporting that various technologies were used in distance education courses Two-way interactive video 49% Internet courses using asynchronous 9% computer-based instruction One-way prerercorded video 7% Other technologies 1% Note: Table made from pie chart.

Unlicensed spectrum, ad hoc networks, things that link, and asynchronous communications will turn telecommunications upside down.