OSI/AS Programming Manual

OSI Upper-Layer Concepts
APS Procedures Programming Concepts
2–4 056783 Tandem Computers Incorporated
Figure 2-1 shows the full sequence of four primitives exchanged for a confirmed
service—a service for which a response is returned.
Figure 2-1. Primitives, Confirmed Service
Your
Application
Request
Confirm
Service
Provider
Indication
Response
Remote
Application
1
4
3
2
015
An example of the sequence of primitives for a confirmed service is described below,
using as the starting point a connect request issued by your application. (The remote
application can, of course, issue requests, too.)
1. To initiate the establishment of a new connection, you call the
APS_ASSOC_CONNECTREQ_ procedure. OSI/AS generates a connect request
primitive and issues it to the service provider.
2. The remote application receives your request as a connect indication primitive.
3. The remote application responds with a connect response primitive.
4. You receive this response as a connect confirm primitive. The receipt of the
primitive is an event. To be notified of an event, you must call
APS_EVENT_RECEIVE_. The sequence of calls you make to receive an event is
described in “Receiving an Event,” later in this section.
Figure 2-2 shows the sequence of primitives to request a service for which no response
is possible. Such a service is called an unconfirmed service.
Figure 2-2. Primitives, Unconfirmed Service
Your
Application
Request
Service
Provider
Indication
Remote
Application
1
2
020