OSI/AS Configuration and Management Manual

OSI/AS Subsystem Description
OSI/AS Configuration and Management Manual—424119-001
7-8
State Machine
State Machine
The TAPS process implements three protocol state machines: session, presentation, and
ACSE.
The Session Layer protocol (described in the ISO 8327 specification) consists of a set of
key states and events that allow for synchronized data transfer between two end systems.
The Presentation Layer protocol (described in the ISO 8323 specification) consists of a
set of key states and events that establish and maintain a context for data interchange.
The ACSE protocol (described in the ISO 8650 specification) consists of a set of key
states and events that assist applications to establish and release associations.
State machine information from the protocols implemented in the TAPS process can be
captured in a trace file. Analysis of the state machine information is enhanced through
the use of the STATETABLES command within PTrace. OSI/AS provides a file,
OSISMT, that you can use with the STATETABLES command to provide enhanced
formatting of state machine transitions.
The following PTrace example shows a Session Layer state machine trace record, after a
CN-SPDU is received. Before receiving a CN-SPDU, the session connection was in an
IDLE state, with a transport connection established (S^STATE^IDLE^TCON^STA01C).
After verifying the CN-SPDU (E^OK), the state machine issues an indication
(ISSUE^SCON^IND) to the user:
15:45:52:650 >000.000 #109 TAPS L5 SM
L5 SM Su Name #Z000002 Session ID 2 Request ID %H80000000
State 00005 -- S^STATE^IDLE^TCON^STA01C
Event 00031 -- E^SPDU^CN
Action 00015 -- CHECK^CN
15:45:52:760 >000.110 #110 TAPS L5 SM
L5 SM Su Name #Z000002 Session ID 2 Request ID %H80000000
State 00036 -- INT^CN^STA01C
Event 00002 -- E^OK
Action 00269 -- ISSUE^SCON^IND