A network of communicating software tasks in a distributed system is considered. Over the period of interest they are permanent concurrent entities, statically allocated to processors. Tasks communicate by messages sent to ports, sockets, or entries. A task execution is such that for each message received on a certain port, a known average number of other actions takes place, including sending of messages and waiting for replies, or reception of messages on some designated port. Various interesting special cases occur. From the behavior model and parameters of each task, network-wide relationships are obtained that govern the rates of intertask messaging. Certain rates may be taken as independent and they determine the remaining rates. In some cases, a narrowly constrained operating subspace results which contains all feasible task-throughput combinations. The relationships cover a variety of types of tasks and types of communication mechanisms, including rendezvous as well as nonblocking send with blocking receive.>