The job of the cop within the transfer layer is

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Unformatted text preview: ts which was input to the sending end would appear at the receiving end. However, space data channels are noisy and may introduce errors or discontinuities into transmitted data streams. The job of the COP within the Transfer layer is therefore to ensure the correctness, completeness and sequentiality of the delivered data units, in the presence of such errors or discontinuities introduced by the layer below. Correctness of the delivered data units is guaranteed (within known error probabilities) by means of the error-protection encoding applied by the Channel Service, and by the Frame Validation Check performed by the Transfer layer. However, validation of the completeness, sequentiality and non-duplication of the delivered data units on a particular Virtual Channel requires that a frame accounting (i.e., numbering) scheme be implemented by the COP. FARM-1 permits Type-AD frames to be accepted only if they are received bearing absolute FRAME SEQUENCE NUMBERS which are in the proper up-counting sequential order; upon detection of the first frame sequence error, the FARM will reject all subsequent TypeAD frames on that Virtual Channel which do not contain the expected FRAME SEQUENCE NUMBER, and the FOP must go back n frames and resume sequential retransmission by repeating all unacknowledged Type-AD frames. Type-BC frames are used to send Control Commands to the FARM. Type-BD frames are processed by the COP only to the extent of causing the FARM to increment the FARM-B COUNTER in the CLCW. CCSDS 202.0-B-2 Page 4-17 CCSDS HISTORICAL DOCUMENT November 1992 CCSDS HISTORICAL DOCUMENT CCSDS RECOMMENDATION FOR TELECOMMAND: DATA ROUTING SERVICE ANNEX A DATA ROUTING SERVICE ACRONYMS AND TERMINOLOGY (THIS ANNEX IS PART OF THE RECOMMENDATION) Purpose: This Annex defines the key acronyms and terms which are used throughout this Recommendation to describe activities within the Segmentation and Transfer Layers. CCSDS 202.0-B-2 Page A-1 CCSDS HISTORICAL DOCUMENT November 1992 CCSDS HISTORICAL DOCUMENT CCSDS RECOMMENDATION FOR TELECOMMAND: DATA ROUTING SERVICE ACRONYMS A: B: CCSDS: CLCW: COP: COP-1: CTRL: FARM: FARM-1: FOP: FOP-1: ID: MAP: MSB: N(R): N(S): QOS: RF or rf: TC: TF: VC: V(R): ACCEPTANCE CHECK MODE BYPASS MODE CONSULTATIVE COMMITTEE FOR SPACE DATA SYSTEMS COMMAND LINK CONTROL WORD COMMAND OPERATION PROCEDURE COMMAND OPERATION PROCEDURE #1 CONTROL FRAME ACCEPTANCE AND REPORTING MECHANISM FARM PART OF COP-1 FRAME OPERATION PROCEDURE FOP PART OF...
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