DNIC

DNIC stands for Data Network Identification Code, a numerical coding scheme used in the era of early packet-switched networks to identify the data network responsible for a transmission. It is typically described as a three-digit code defined by international standards and used within X.25 addressing and routing frameworks. In this context, the DNIC forms part of the international address that directs a data call to the appropriate national or organizational data network, where it is combined with additional local addressing components to reach the final destination.

Historically, DNICs were allocated to national networks or major carriers and administered by national telecommunications authorities or designated operators. The DNIC concept facilitated routing across international networks by providing a standardized identifier for the originating data network, thereby supporting interworking between different national systems in the pre‑IP era.

With the widespread adoption of Internet Protocol (IP) based technologies and the decline of X.25, the practical use of DNICs has diminished. Today, they are largely of historical or interoperability interest, appearing in archival documentation, legacy equipment, or studies of the evolution of network addressing schemes.

See also X.25, X.121, and ITU-T.