The ACSE supports two modes of communication: connection-oriented and connectionless. The ACSE service definition (ITU-T Rec. X.217 | ISO/IEC 8649) includes both modes of communication. This Protocol Specification provides the protocol specification for the connection-oriented mode of communication. The protocol specification for the connectionless mode of communication is contained in ITU-T Rec. X.237 | ISO/IEC 10035-1.

This Protocol Specification defines procedures that are applicable to instances of communication between systems which wish to interconnect in an Open Systems Interconnection environment in a connection-oriented mode. The Protocol Specification includes the Kernel functional unit that is used to establish and release application-associations. The Authentication functional unit provides additional facilities for exchanging information in support of authentication during association establishment without adding new services. The ACSE authentication facilities can be used to support a limited class of authentication methods. The Application Context Negotiation functional unit provides additional facility for the selection of the application context during association establishment.

This Protocol Specification specifies:

• procedures for the transfer of information for application-association control and the authentication of application-entities;
• the interaction between an ACSE protocol machine and the occurrence of external presentation events; and
• the abstract syntax for the representation of the ACSE APDUs.

The ACSE procedures are defined in terms of:

• the interactions between peer ACSE protocol machines through the use of presentation-services; and
• the interaction between an ACSE protocol machine and its service-user.

This Protocol Specification also specifies conformance requirements for systems implementing these procedures. It does not contain tests which can be used to demonstrate conformance.