This Recommendation | International Standard defines in an abstract way the externally visible service provided by the OS1 Session Layer in terms of:

• the primitive actions and events of the service;
• the parameter data associated with each primitive action and event;
• the relationship between, and the valid sequence of these actions and events.

The service defined in this Recommendation | International Standard is that which is provided by the OS1 session protocol (in conjunction with the transport service) and which may be used by the OS1 presentation protocol.

This Recommendation | International Standard does not specify individual implementations or products, nor does it constrain the implementation of entities and interfaces within a computer system. There is, therefore, no conformance to this Recommendation | International Standard.

The text pertaining to the symmetric synchronization functional unit is not applicable to the support of ITU-T applications.