Iberpac (or Red UNO) was the Spanish packet switched X.25 public data network.
[2][3][4] The original Red Secundaria de Alto Nivel (RSAN) protocols for RETD were custom-developed by Telefónica (then CTNE) under ARPANET design principles.
By 1978, project TESYS (Telefónica, SECOINSA, SITRE) started the development of specific-purpose switching nodes.
Some of the design principles of TESYS nodes were advanced for their time (multithreading, token passing protocols).
In contrast, the large user base with terminals based on legacy RSAN protocols slowed the adoption of X.25, TESYS product development and support were targeted to CTNE only (thus precluding the spread of TESYS to international markets) and data lines in Spain became slow for their time (only 2% lines above 1200 bit/s in Spain in 1982, compare 89% in West Germany).