In article on the basis of the theory of networks of queuing network structures (subnets and a LAN) taking into account heterogeneity of their traffic are researched. The research technique is grounded on an analytical method two-dimensional diffusion approximating of systems of queuing GI/G/1 of a general view and solution of the equations of balance of streams at level of the two first moments (average values and dispersions) allocations of intervals of times of arrival and service. Such approach at definition of characteristics of functioning of networks allows improving results of modeling essentially.