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In normal operation for a near-Earth mission, the value for T1_Initial is set to slightly more than the
expected round trip time from a frame leaving FOP-1 to an acknowledging CLCW arriving back at
FOP-1. To cause multiple transmissions of a sequence of frames for a deep space mission, T1_Initial
and other parameters can be used differently. For example:
− The management entity sets T1_Initial to a value that is much shorter than the round-trip time and it
sets the option to use the Suspend / Resume mechanism. − FOP-1 transmits the frames in the sequence once as normal.
internal Sent_Queue. − Before any CLCWs can arrive to acknowledge receipt of the frames, the timer expires, so FOP-1
retransmits all the frames in the Sent_Queue. This repeats until the transmission limit is reached. − In normal operation for a near-Earth mission, FOP-1 reports a failure when it reaches the
transmission limit and it stops the sequence-controlled service and clears the Sent_Queue. In this
example, FOP-1 suspends and it does not clear the Sent_Queue. − At a later time, the management entity can adjust parameters and then reactivate FOP-1 with a
Resume directive. FOP-1 keeps the frames in its However, this requires actions by the management entity, in addition to the usual actions to start and
stop the sequence-controlled service. The management entity has to select appropriate values for the
FOP-1 parameters to force the early retransmissions. It also has to handle a FOP-1 suspend and
make decisions about the timing for Resume.
Therefore, if a deep space mission is going to use this method of forcing the early automatic
retransmissions, then the automation of the management entity is complex, or else the management
relies on human intervention. The intention of the proposed new systematic retransmissions is to
provide the user with the retransmissions but without the complex management. TCretrans7 2008Sep09 I.B. + M.A. DE LANDE LONG
SOFTWARE + CONSULTANCY
Options for repeated retransmissions for te...
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- Spring '14