33 virtual channel reception function 4331 the

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Unformatted text preview: hannel. 4.3.3.2 The Virtual Channel Reception Function shall extract data units contained in the Data Field of the Transfer Frames, and deliver them to its user (i.e., the Packet Extraction Function or the VCA Service user). 4.3.3.3 If there is a user of the VC_FSH Service for a particular Virtual Channel, FSH_SDUs contained in the Transfer Frame Secondary Header of the Transfer Frames shall be extracted and delivered to the user. If there is a user of the VC_OCF Service for a particular Virtual Channel, OCF_SDUs contained in the Operational Control Field of the Transfer Frames shall be extracted and delivered to the user. NOTE – If a gap in the Virtual Channel Frame Count is detected, a Loss Flag is optionally delivered to the users. 4.3.3.4 An abstract model of the Virtual Channel Reception Function is illustrated in figure 4-14. CCSDS 132.0-B-1 Page 4-23 September 2003 CCSDS RECOMMENDATION FOR TM SPACE DATA LINK PROTOCOL Only one of these two entities exists for a Virtual Channel Packet Extr. Function Transfer Frame Data Fields Virtual Channel Reception Function for a Virtual Channel VCA Service User VC_FSH Service User VCA_SDUs VC_OCF Service User FSH_SDUs OCF_SDUs Decommutation VC Frames Virtual Channel Demultiplexing Function Figure 4-14: Abstract Model of Virtual Channel Reception Function 4.3.4 VIRTUAL CHANNEL DEMULTIPLEXING FUNCTION 4.3.4.1 The Virtual Channel Demultiplexing Function shall be used to demultiplex Transfer Frames of different Virtual Channels of a Master Channel. NOTE – There is an instance of the Virtual Channel Demultiplexing Function for each Master Channel that has multiple Virtual Channels. 4.3.4.2 The Virtual Channel Demultiplexing Function shall examine the VCID in the incoming stream of Transfer Frames and shall route them to the instances of the Virtual Channel Reception Function and, if present, to the Virtual Channel Frame Service users. NOTES 1 If a gap in the Virtual Channel Frame Count is detected, a Loss Flag is optionally delivered to the users. 2 Transfer Frames with an invalid VCID are discarded. 4.3.4.3 An abstract model of the Virtual Channel Multiplexing Function is illustrated in fi...
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