We introduce a class of networks called Isotach networks designed to reduce the cost of synchronization in parallel computations. Isotach networks maintain an invariant that allows each process to control the logical times at which its messages are received and consequently executed. This control allows processes to pipeline operations without sacrificing sequential consistency and to send isochrons, groups of operations that appear to be received and executed as an indivisible unit. Isochrons allow processes to execute atomic actions without locks. Other uses of Isotach networks include ensuring causal message delivery and consistency among replicated data. Isotach networks are characterized by this invariant, not by their topology. They can be implemented in a wide variety of configurations, including NUMA (nonuniform memory access) multiprocessors. Empirical and analytic studies of Isotach synchronization techniques show that they outperform conventional techniques, in some cases by an order of magnitude or more. Results presented here assume fault-free systems; we are exploring extension to selected failure models.