OSI/FTAM Programming Reference Manual

Running H/F 1
HP NonStop OSI/FTAM Programming Reference Manual—528611-001
3-3
Running H/F 2
Initiator Data Flow
An FTAM application can send FTAM requests and responses and receive confirms
and indications, as outlined later in this section. This subsection specifically describes
the flow of an FTAM request from the NonStop FTAM application to the responding
system, and the flow of the remote responder’s response back to the NonStop FTAM
application in the form of a confirm.
The sequence of steps below assumes that you have already established an
association. The numbers shown in Figure 3-1 on page 3-2 correspond to the
sequence of steps outlined below.
1. The FTAM application issues a procedure call through the FTAM API, which
performs some verification and, if necessary, rejects the call with the appropriate
error.
2. If the FTAM API verifies the procedure call to be valid, it sends the appropriate
FTAM request primitive to the FTAM initiator.
3. When the initiator receives the service request, it sends the request directly to the
protocol state machine, where it is processed. The protocol state machine does
some limited error checking, and when it detects an FTAM protocol error or other
error, it sends an error message to the application through the FTAM API and
discontinues processing the request.
4. If the FTAM request is valid, the protocol state machine sends the request through
the OSI/AS API to the TAPS process of the OSI/AS subsystem.
5. The TAPS process receives the FTAM request protocol data unit (PDU), formats it
as an appropriate protocol data unit, and forwards it to the appropriate TSP
process.
6. The TSP process, in turn, processes the information received from TAPS, formats
it as a transport protocol data unit (TPDU), and forwards it to the NSP process.
7. The NSP process formats the PDU and, depending on the network protocol that
the NSP process supports (TLAM or X25AM, for example), forwards it via the
appropriate controller over the network to the responding system, where it is
received as an indication.
8. The responding system processes the indication and sends back a response.
The NonStop initiating system then receives the response as a confirm and sends it up
through the NSP, TSP, and TAPS processes for processing. After processing it, the
TAPS process sends the confirm information through the OSI/AS API to the FTAM
initiator. Once in the FTAM initiator, the protocol state machine verifies, processes, and
sends it to the application via the FTAM API.
The configuration of NonStop FTAM and OSI/AS determines the selection of the TAPS,
TSP, and NSP processes to be used for an association. For more information on
configuration, see the OSI/FTAM Configuration and Management Manual. For
additional details on the upward and downward flow of information between TAPS,