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Unformatted text preview: P-1 is unable to guarantee that an FDU was transferred to the receiving end despite
retry attempts, a ‘Negative Confirm Response to Request to Transfer FDU’ for that FDU
shall be passed to the Higher Procedures. FDUs for which a ‘Negative Confirm Response’ is
received may or may not have been successfully transferred. Therefore, a ‘Negative Confirm
Response’ shall signal a break in the Sequence-Controlled Service guarantee.
The ‘Negative Confirm Response to Request to Transfer FDU’ does not carry a parameter
giving the reason for the failure to confirm the requested data transfer service. However,
whenever a condition is detected which might give rise to such responses, an ‘Alert’
notification shall be signaled from FOP-1.
From the point of view of the Higher Procedures, between the time of acceptance of an FDU
by FOP-1 until a ‘Positive Confirm Response’ is received, the FDU is in a ‘gray area’ in
which it is not possible to know if it has been transferred to the receiving end. If an FDU has
not been accepted by FOP-1, it is deemed to be still under the control of the Higher
Procedures and is not covered by the Sequence-Controlled Service guarantee. Once FOP-1 CCSDS 232.1-B-2 Page 4-8 September 2010 RECOMMENDED STANDARD FOR COMMUNICATIONS OPERATION PROCEDURE-1 detects a problem (for example, a failure of the automatic error-recovery mechanism to
ensure transfer) leading to a break in the Sequence-Controlled Service guarantee, it shall
reject the outstanding ‘Request to Transfer FDU’. Therefore, an FDU which has not been
accepted can never be in the ‘gray area’.
Once either a ‘Positive Confirm Response to Request to Transfer FDU’ or a ‘Negative
Confirm Response to Request to Transfer FDU is returned, no further action shall be taken
by FOP-1 for the corresponding Request.
4.4.3 TRANSFER NOTIFICATIONS FOR TYPE-B (OR BD) SERVICE After each ‘Request to Transfer FDU’ from the Higher Procedures (see 126.96.36.199.2), either
immediately or after a delay, FOP-1 returns to the Higher Procedures either an ‘Accept
Response to Request to...
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This document was uploaded on 03/06/2014.
- Spring '14