In practice, such services may not be provided by a single, discrete, end-to-end cable, but they do provide guarantees of constant bandwidth availability and near-constant latency, properties that cannot be guaranteed for more public systems. Such properties add a considerable premium to the price charged.
As more general-purpose systems have improved, dedicated lines have been steadily been replaced by intranets and the public Internet, but they are still useful for time-critical, high-bandwidth applications such as video transmission.
See also : ATM, Frame relay, T-carrier