OSI/AS SCF Reference Manual

OSI/AS Trace Facility
OSI/AS SCF Reference Manual—424121-001
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Structure of the OSI/AS Processes
Structure of the OSI/AS Processes
Figure 3-1 illustrates the architecture of a user application process and the OSI/AS
subsystem processes (and lower layer processes) from the perspective of how tracing
works.
Legend
1–4: The OSI manager process manages the OSI subsystem configuration. Among other tasks, the OSI manager
establishes communication paths through the subsystem by adding subdevices (SUs) to both TAPS and TSP
processes. This OSI manager action follows a user application call to APS_ASSOC_ATTACH_ or
APS_ASSOC_CONNECTREQ_. APS requests the OSI manager to assign the subdevice names and set up the
path, and then adds the subdevices and replies to APS with a TAPS process name and subdevice name. APS opens
the TAPS subdevice which causes TAPS to open the TSP subdevice.
5–7: The OSI manager process is not involved once the connection has been established. User requests flow from
the APS application through the subsystem processes mirroring the OSI model of request or response primitives
passing down through the 7 OSI layers. OSI indication or confirm primitives flow up to the APS user through the
same set of subsystem processes.
TAPS Process Structure
Figure 3-2 shows the contents of a TAPS process.
Figure 3-1. Structure of the OSI/AS Processes
NSP processes [X25AM,
TLAM (for D-series), or
PAM (for G06 and later)]
communicate with
hardwire devices
NSP
TSP
TAPS
APS User
Application
OSI Manager
MIB
1
2
3
5
6
User programs make APS
procedure calls
TAPS processes provide
ACSE, Presentation, and
Session Layer services
TSP processes provide
transport and some of the
Network Layer services
4
7
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