Title: CPDLC - Forward Error
     
PDR Reference:                          	99120001
Originator Reference:                   	G. Saccone
SARPs Document Reference:               	CPDLC SARPs, 2.3.5.5.3.3, 2.3.5.5.13.1 
Status:                                 	RESOLVED
Impact:					     	B (bug) 
PDR Revision Date:                      	25/08/00 (PROPOSED -> RESOLVED)
							14/08/00 (ACCEPTED -> PROPOSED)
						  	06/12/99 (SUBMITTED -> ACCEPTED) 
PDR Submission Date:                    	06/12/99
Submitting State/Organization:          	WG3/SG2
Submitting Author Name:                 	G. Saccone 
Submitting Author E-mail Address:       	gsaccone@ons.com 
Submitting Author Supplemental
Contact Information:
SARPs Date:                             	ICAO 9705 Edition 2 and Edition 3
SARPs Language:                         	English
     
Summary of Defect:
     
There are some omissions for the CPDLC-forward service.  In 2.3.5.5.13.1, the sending CPDLC-ground-ASE does not set the D-START Request DS User Version parameter to the value of the sending CPDLC ASE.  This means that the receiving CPDLC-ground-ASE will not be able to perform the version checking that is done in 2.3.5.5.2.3.

Also, upon receipt of the D-START ind containing the ATCForwardMessage, the only time the version number is set in the D-START rsp is when the version numbers are not equal.  If the service is not supported or if the version numbers are equal, only the Result is set (to "service-not-supported" or "success",  respectively).  Therefore, the checks as performed in 2.3.5.5.3.3 will not work, since they sending CPDLC-ground-ASE checks the D-START confirmation DS User Version number to see if the versions are equal (which it will never be since it is not provided in the D-START rsp), and additionally the "service-not-supported" will never get to the sending CPDLC-ground-user since there is no protocol to indicate it.

Proposed SARPs Amendment:

2.3.5.5.3.3:

Replace a)-b) with:

a)	Stop timer tstart,

b)	invoke CPDLC-forward service confirmation with:

	1)	the D-START GroundPDUs APDU element as the CPDLC-forward service Result parameter value, and

	2)	if provided, the D-START DS User Version Number parameter value as the CPDLC-forward service ASE Version Number parameter value, and

c)	enter the IDLE state.

2.3.5.5.13.1:

Add new number 3) under letter b):

3)	the sending CPDLC-ground-ASE version number as the D-START DS User Version Number parameter value,

Impact on interoperability: If not implemented, two versions 1 system can not establish a CPDLC forward dialogue

Assigned SME:                       SME2
          
SME Recommendation to CCB:		-
     
CCB Decision:                      	CCB-11 (Tokyo): ACCEPTED (6/12/99) 
						atnp_ccb_chair: PROPOSED (14/08/00)
						CCB-12 (Berlin): RESOLVED (25/08/00)