A direct data link connects two communication partners. The link is permanently established via a network or a dedicated line and does not need to be connected or disconnected as in the case of a dial-up line. A DDL can be used to transfer digital data for various applications such as phone calls, videos, or computer communication. In addition to physical direct data links in the form of copper pairs or fibre-optic cables, for example, many of these point-to-point connections are based on superordinate network infrastructures such as ATM or SDH. One key characteristic of a DDL is the bit-transparent transfer.
When setting up a direct data link, the network provider establishes a direct communication relationship between the two parties. Deutsche Telekom uses the term “direct data link” (Datendirektverbindung - DDV) as a product name for specific types of dedicated lines with high availability and a low error rate.