Network technologies have been progressing rapidly toward  faster and larger networks which are capable of providing integrated services. These technical developments in turn require advances in analytic methodologies that can be effectively used in the design and control of future networks such as ATM-based B-ISDN, all-optical networks and wireless communication networks. Emerging high-speed integrated communication services require us to analyze  network systems, in which information loss probabilities range from  10**-2 (e.g., call connection loss) to as small as 10**-10 (e.g.,  ATM cell loss). In this proposed study we will develop a theoretical foundtion for evaluation and control of connection-oriented services, which in particular will enable us to handle this wide range of loss probabilities. We begin by generalizing the product form solutions obtained for loss networks with fixed routing. Our formulation encompasses a broad range of state-dependent call generation  patterns, different types of network services, and the whole range  of traffic levels. Using our experience in computational algorithms for closed queueing network models, we will develop new practical methods for estimating loss probabilities in connection-oriented services. In order to insure the accuracy of approximate formulas, we will develop appropriate error bounds. A refinement and a rigorous validation of the reduced load approximation method, also referred to as the Erlang's fixed point method in the case of Poisson arrivals, will be attempted for networks with state dependent arrivals. In parallel with the above algorithmic and asymptotic methods, we will explore a model of connection-oriented network services  based on a multi-dimensional Ornstein-Uhlenbeck diffusion process. The diffusion process approach will allow  us not only to evaluate  more general types of networks (i.e.,  loss/queueing networks not  amenable to product form solutions) but  also to obtain  time-dependent, i.e., transient, solutions for network behavior. Finally, we will formulate and  solve network control policy  problems such as call admission control and routing decisions.