The ISO Association Control Service Element (ACSE), an application layer protocol in the OSI model, is to establish and release an application-association between two AEIs and to determine the application context of that association. The ACSE supports two modes of communication: connection-oriented and connectionless. For the connection-oriented mode, the application-association is established and released by the reference of ACSE connection oriented services. For the connectionless mode, the application-association exists during the invocation of the single ACSE connectionless mode service, A-UNIT-DATA.
The applications in the OSI reference model represent communication between a pair of application-processes (APs) in terms of communication between their application-entities (AEs) using the presentation-service. The functionality of an AE is factored into a number of application-service-elements (ASEs). The interaction between AEs is described in terms of the use of their ASEs? services. This Service Definition supports the modeling concepts of application-association and application context.
An application-association is a cooperative relationship between two AEIs. It provides the necessary frame of reference between the AEIs in order that they may interwork effectively. This relationship is formed by the communication of application protocol control information between the AEIs through their use of the presentation-service.
An application context is an explicitly identified set of application-service-elements, related options and any other necessary information for the interworking of application-entities on an application association.
The ACSE service-user is that part of an application-entity that makes use of ACSE services. It may be the Control Function (CF) or an ASE or some combination of the two.
The services provided by ACSE are listed as follows:
| Communication mode | Service | Type |
| Connection oriented | A-ASSOCIATE A-RELEASE A-ABORT A-P-ABORT |
Confirmed Confirmed Non-confirmed Provider-initiated |
| Connectionless | A-UNIT-DATA | Non-confirmed |
Protocol Structure
The functions, services and message structure are listed as follows:
| Functional Unit | Service | APDU | Field Name |
| Kernel | A-ASSOCIATE | AARQ | Protocol Version Application Context Name Calling AP Title Calling AE Qualifier Calling AP Invocation-identifier Calling AE Invocation-identifier Called AP Title Called AE Qualifier Called AP Invocation-identifier Called AE Invocation-identifier Implementation Information User Information |
| AARE | Protocol Version Application Context Name Responding AP Title Responding AE Qualifier Responding AP Invocation-identifier Responding AE Invocation-identifier Result Result Source-Diagnostic Implementation Information User Information |
||
| A-RELEASE | RLRQ | Reason User Information |
|
| RLRE | Reason User Information |
||
| A-ABORT | ABRT | Abort Source User Information |
|
| Authentication | A-ASSOCIATE | AARQ | ACSE Requirements Authentication-mechanism Name Authentication-value |
| AARE | Ditto | ||
| ABRT | Diagnostic | ||
| Application Context Negotiation |
A-ASSOCIATE | AARQ | Application Context Name List ACSE Requirements |
| AARE | Ditto |
Related protocols: Session Protocol, Presentation Protocol, ROSE
Sponsor Source: The ACSE protocol is defined in ISO (http://www.iso.org) documents 8650 and 8649 and ITU (http://www.itu.org) documents X.217, X.227, X.237.
Reference:
http://www.doc.ua.pt/arch/itu/rec/product/X.htm:
X.217: Information technology - Open Systems Interconnection - Service definition for the Association Control Service Element
X.227: Information technology - Open Systems Interconnection - Connection-oriented protocol for the Association Control Service Element: Protocol specification
X.237: Information technology - Open Systems Interconnection - Connectionless protocol for the Association Control Service Element: Protocol specification