Today’s Internet rests upon not only on highly developed computer technology. The Internet bases as well on data transmission on public telephone networks which is indispensable for it. Nevertheless computer communications have been considered less in the major history of computing. To a greater extent this lack has to be recognized in the history of computer networks technology in Eastern Europe. Already in 1953 specialists of the Institute of Precision Mechanics and Computer Machinery in Moscow started developing a computer-based missile defense system in which radar signals had to be transmitted to central computers over long distances. In the 1960s in USSR and other COMECON countries more and more networks for civil purposes had been developed, in particular at large scientific institutes, e.g. the Joint Institute for Nuclear Research in Dubna or the Institute for High Energies Moscow. In 1969 the decision to produce the Rjad computer system which was modeled on the IBM 360 system led to stronger orientation of Eastern computers on Western technology. However, there existed a time gap of some years. Additionally, in the 1960s increasingly computer systems were used for civil purposes. In particular the political leadership hoped to improve the central planning system by using data processing machines. Consequently the Rjad system had been completed with several data transmission components. Furthermore since the 1970s, at nearly all COMECON countries, universities and institutes of the Academies of Science built up computer networks. Similar to the West those local networks were connected via the public telephone system. The paper deals with the opportunities and the limits of computer networking in COMECON countries. It discusses technical and economical problems.