The mathematical and algorithmical aspects of the network model, which are the basis of the “Computer Programme System Network Technique” developed in the College of Civil Engineering Leipzig, are discussed in this paper. The general coupling conditions for proedures which are used lead to the common data calculation appearing as an essentially more general linear optimization problem than it is in the case in usual network models. Algorithms for calculating the lastest starting times are given as well as an algorithm for finding an admissible data-timesystem. The latter works by using a combinatorial optimization method similar to Minty's algorithm. A more detailed description of this method is presented.