Title: ADS - Erroneous exception handling for D-DATA indication

PDR Reference:                  	98050008
Originator Reference:            	ATNSI_ADS05 
SARPs Document Reference:        	ADS SARPs, Section 2.2.1.5.4.3.3
Status:                           	RESOLVED 
Impact :					C (Clarification)
PDR Revision Date:               	25/06/98 (PROPOSED RESOLVED)
						20/06/98 (SUBMITTED -> ACCEPTED -> PROPOSED)
PDR Submission Date:               	12/05/98 
Submitting State/Organization:    	AIRSYS ATM (ACI/ATNSI)
Submitting Author Name:           	Ilkiewicz, M / Stokes, S.
Submitting Author E-mail Address:          											michel.ilkiewicz@cdv.vly.sextant.thomson.fr 
					Shawn.Stokes@ATNSI.COM 
Submitting Author Supplemental 
Contact Information:                       
SARPs Date:                      	IV2.2, March 98
SARPs Language:                 	English

Summary of Defect:

The air LI module does not request the AB module to abort with reason "invalid-PDU" on receipt of a D-DATA indication containing an ADS-cancel-all-contracts PDU.

This is erroneous, since a SARPs conformant ground ASE does not send this PDU in a D-DATA request (always in a D-END data).

Impact on Safety:

If not corrected, and if  the ground ASE sends by error the ADS-cancel-all-contracts PDU in a D-DATA request, the air LI module will not detect the error, as it should do, and will invoke the ADS-cancel-all-contracts indication to the ADS-air-user. However, the DC, EC, PC and EM modules won't be stopped and the ADS-positive-acknowledgment PDU (cancel-all-contracts) will not be sent to the ground LI as stated in section 2.2.1.5.3.16.7.1.1. 

This abnormal state will cause later on an abort (probably because of the t-end timeout) with no way for the controller to understand the real origine of the fault. 

Assigned SME:              	Sub-Volume II SME

Proposed SARPs amendment: 

The list of valid APDUs in D-DATA indications which do not lead the LI module to request the AB module to abort with reason invalid-PDU should be reduced by excluding ADS-cancel-all-contracts PDUs, i.e. in section 2.2.1.5.4.3.3 take out ", an ADS-cancel-all-contracts". 

Change 2.2.1.5.4.3.3 from:

2.2.1.5.4.3.3 When the user data parameter value of a D-DATA indication is a valid APDU and is not an ADS-demand-contract-PDU, an ADS-event-contract-PDU, an ADS-periodic-report-PDU, an ADS-modify-emergency-contract-PDU, an ADS-cancel-emergency-acknowledgment-PDU, an ADS-cancel-all-contracts-PDU or an ADS-cancel-contract-PDU, the air LI module shall request the AB module to abort with reason <invalid-PDU>.

to:

2.2.1.5.4.3.3 When the user data parameter value of a D-DATA indication is a valid APDU and is not an ADS-demand-contract-PDU, an ADS-event-contract-PDU, an ADS-periodic-report-PDU, an ADS-modify-emergency-contract-PDU, an ADS-cancel-emergency-acknowledgment-PDU or an ADS-cancel-contract-PDU, the air LI module shall request the AB module to abort with reason <invalid-PDU>.

SME Recommendation to CCB:                 	

CCB Decision:                atnp_ccb_chair: SUBMITTED (12/05/98)
					atnp_ccb_chair: ACCEPTED (11/06/98)
					CCB-6 (Utrecht): RESOLVED (25/06/98)