OSI/FTAM Programming Guide

ISO FTAM Concepts
HP NonStop OSI/FTAM Programming Guide—528612-001
2-5
Services
Services
The FTAM protocol consists of distinct services. These services, in turn, are made up
of primitives, which are the smallest units of interaction between the FTAM user and
the FTAM service provider. Services fall into two categories: confirmed and
unconfirmed services.
Confirmed Versus Unconfirmed Services
In a confirmed service, the FTAM initiator sends a request to the FTAM responder. The
responder receives this request as an indication, performs the service, and then
returns a response. The response is received as a confirm by the initiator. The confirm
primitive notifies the initiator of the results of the responder’s attempt to perform the
requested service. Most FTAM services are confirmed services.
An unconfirmed service is one in which the FTAM initiator does not receive a confirm to
a service request. In an unconfirmed service, the initiator sends a request to the FTAM
responder. The responder receives this request as an indication, but does not return a
response. In this case, you do not determine the status of your service request through
a corresponding confirm; that is, the request is unconfirmed. Unconfirmed services
include abnormally ending an association, issuing read or write requests, and
transferring data.
Figure 2-2 on page 2-6 illustrates the relationship of request-indication, response-
confirm primitive pairs in FTAM confirmed and unconfirmed services. This figure is a
simple protocol diagram, which represents the movement of FTAM PDUs back and
forth across the network in an FTAM association. A PDU is the encoded message that
is transferred across the network between an initiator and responder. The parameters
associated with an FTAM primitive are encoded into a PDU for transfer across the
network. The PDU is decoded and interpreted as a primitive once it is received at its
destination.