Defines OSI Network Service concerning primitive actions and events, the corresponding parameters and their Forms, and the interrelationsship between them as well as the valid sequences. Specifies characteristics of a conceptual Network Service and supplements the reference model by guiding the development of Network Layer protocols, convergence of subnetwork capabilities, bases of individual extensions of heterogenous subnetworks to a common subnetwork-independent Network Service, and of the development and implementation of Transport Layer protocols regardless of subnetworks and the variability of underlying public and private subnetworks and their specific interface requirements.