Ccsds 1320 b 1 page 2 14 september 2003 ccsds

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Unformatted text preview: 1 Page 2-14 September 2003 CCSDS RECOMMENDATION FOR TM SPACE DATA LINK PROTOCOL 3 3.1 SERVICE DEFINITION OVERVIEW This section provides service definition in the form of primitives, which present an abstract model of the logical exchange of data and control information between the protocol entity and the service user. The definitions of primitives are independent of specific implementation approaches. The parameters of the primitives are specified in an abstract sense and specify the information to be made available to the user of the primitives. The way in which a specific implementation makes this information available is not constrained by this specification. In addition to the parameters specified in this section, an implementation may provide other parameters to the service user (e.g., parameters for controlling the service, monitoring performance, facilitating diagnosis, and so on). 3.2 SOURCE DATA 3.2.1 SOURCE DATA OVERVIEW NOTE – This subsection describes the service data units that are transferred from sending users to receiving users by the TM Space Data Link Protocol. The service data units transferred by the TM Space Data Link Protocol are as follows: a) Packet; b) Virtual Channel Access Service Data Unit (VCA_SDU); c) Frame Secondary Header Service Data Unit (FSH_SDU); d) Operational Control Field Service Data Unit (OCF_SDU); e) TM Transfer Frame. 3.2.2 PACKET 3.2.2.1 Packets shall be transferred over a space link via the Packet Service. 3.2.2.2 The Packets transferred by this service must have a Packet Version Number (PVN) authorized by CCSDS. Further, each Packet transferred must conform to the corresponding packet format specified by reference [4]. 3.2.2.3 The position and length of the Packet Length Field of the Packets must be known to the service provider in order to extract Packets from Transfer Frames at the receiving end. CCSDS 132.0-B-1 Page 3-1 September 2003 CCSDS RECOMMENDATION FOR TM SPACE DATA LINK PROTOCOL NOTES 1 Packets are variable-length, delimited, octet-aligned data units, and are usually the protocol data unit of a Network Layer protocol. 2 For the PVNs presently aut...
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