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Association Control Service Elements (ACSEs)

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Downloads to date: N/A | Words: 2400 | Submitted: 2008-06-14

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Purpose of ACSE

• To set up and maintain an application Association between two co-operating Application Processes [i.e. Two application specific ASEs (SASEs)]
• And more specifically between two Application Entities (AEs : Set of Application Service Elements (ASEs)) which are responsible for communication between the APs on different open systems.

Normally, an Association is established in response to a request from a client user Application Process for access to a particular networked service, such as a file server. To perform such services in an open way, a separate SASE is associated with each service present in the application layer in each networked system (computer). At one side it is known as the client ASE and at the other as the server ASE.

A single ASE in each open system will use ACSE, possibly on behalf of 'Superior' ASEs in the same open system.

Normally on the receipt of an initial service request from the client user Application Process, the client SASE first creates its own initialise (connection-receipt) PDU (Protocol Data Unit) and then uses the services provided by the ACSE to establish an Association with the correspondent (called) SASE. The initialise PDU, together with other information such as address of the calling and called SASEs, are passed with the ACSE associate request service primitive.

Application Association

This is a co-operative relation-ship between two ASEs and defines their terms of reference. The association determines which application protocols will communicate, and how they will do so; including their use of the presentation service.

Once an association has been established, ACSE does not feature in the subsequent SASE dialogue until the latter requests that the association be released (disconnected).

We will now look at the service primitives associated with ACSE.


ACSE Service

As is usual with OSI SEs, various services are defined in terms of service primitives. ACSE offers services:
• One for handling the set-up of the association
• One for handling graceful termination of the association
• Two for handling abnormal terminations.

At present, each service is associated with a single service primitive, although mechanisms for the provision of additional facilities, which the association details during its currency, are currently under consideration.


Associate Service

• This sets up an association.
• A single primitive is provided.
• 31 possible parameters => it is exceedingly complex.
• We will discuss only a few classes of parameter here:
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