Title:          	 ACSE generates P-U-Abort req when CF is in NULL state 
PDR Reference:                          9706-0026
Originator Reference:                   UL-DR 117
SARPs Document Reference:               ULCS SARPs 4.3.3.1.2, 4.3.3.5.3.1
Status:                                 RESOLVED
PDR Revision Date:                      30/10/97
PDR Submission Date:                    27/06/97
Submitting State/Organization:          ATNP/WG3/SG3 
Submitting Author Name:                         KERR, A
Submitting Author E-mail Address:       tony.kerr@level-7.co.uk 
Submitting Author Supplemental          tel: +44 1344 867199
Contact Information:                    fax: +44 1344 868442 
SARPs Date:                             Proposed ICAO Version 2.0
					(WG3 Thailand, Mar 97) 
SARPs Language:                         English

Summary of Defect:

The problem occurs if the ACSE protocol machine detects a protocol error (unexpected APDU received, or invalid field encountered during processing of incoming APDU).  According to ISO/IEC 8650, it a) issues an A-ABORT indication to its service-user and b) subsequently issues an ABRT APDU as user data on a P-U-ABORT request primitive.  The A-ABORT indication causes the CF to move to the NULL state, which means that the P-U-ABORT request is then treated as an error condition.


Assigned SME:                           Sub-Volume 4 SME

SME Comment:

Reconsideration of UL-DR 114 suggests that changes to the ULCS SARPs are necessary as "Blank cell" conditions in the State Table are supposed to be "impossible".  Therefore, if a valid scenario is found such that a blank cell in the ULCS state table is encountered, then there is a defect in the ULCS SARPs.

The solution in this case should be to accept a P-U-ABORT request from the ACSE lower service boundary when the CF is in the NULL state.  The P-U-ABORT will always have an ABRT APDU as user-data, and the abort source field will be "ACSE service-provider" (see 7.3.3.4 of ACSE protocol spec).


Proposed SARPs amendments:

1. Modification to section 4.3.3.1.2 (Table 4.3-4):

Original text:
Cell (P-U-ABORT req (data), STA 0) is currently blank. Replacement text:
Insert the following in cell (P-U-ABORT req (data), STA 0):
STA0
P-U-ABORT req

2. Modification to section 4.3.3.5.3.1:

Delete ", except the NULL state; if an invocation occurs when the CF is in the NULL state then an error has occurred (see 4.3.3.1.2.4)"

The clause now reads:
Invocations of the P-U-ABORT Request primitive by the ACPM shall be allowed when the CF is in any valid state.

SME Recommendation to CCB:  RESOLVE by accepting the proposed amendment.

CCB Decision: RESOLVED (30/10/97)