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Unformatted text preview: Systems Interconnection—Basic Reference Model:
The Basic Model. International Standard, ISO/IEC 7498-1. 2nd ed. Geneva: ISO,
1994.  Information Technology—Open Systems Interconnection—Basic Reference Model—
Conventions for the definition of OSI services. International Standard, ISO/IEC
10731:1994. Geneva: ISO, 1994.  TC Space Data Link Protocol. Recommendation for Space Data System Standards,
CCSDS 232.0-B-2. Blue Book. Issue 2. Washington, D.C.: CCSDS, July 2010. NOTE – Informative references are listed in annex B. CCSDS 232.1-B-2 Page 1-5 September 2010 RECOMMENDED STANDARD FOR COMMUNICATIONS OPERATION PROCEDURE-1 2
CONCEPT OF COP-1 The Communications Operation Procedure-1 (COP-1) is a closed-loop procedure executed
by the sending and receiving ends of the TC Space Data Link Protocol (reference ). COP1 utilizes an Automatic Request for Retransmission (ARQ) procedure of the ‘go-back-n’ type
to retransmit Transfer Frames that were rejected by the receiving end of the protocol. COP-1
allows Type-A Transfer Frames to be accepted by the receiving end only if they are received
in strict sequential order. This enables the service data units to be delivered correctly to the
layer above at the receiving end, without omission or duplication, and in the same sequential
order in which they were received from the layer above at the sending end.
COP-1 consists of a pair of synchronized procedures for each Virtual Channel: a Frame
Operation Procedure-1 (FOP-1) that executes within the sending entity, and a Frame
Acceptance and Reporting Mechanism-1 (FARM-1) that executes within the receiving entity.
The FOP-1 transmits Transfer Frames of a particular Virtual Channel to the FARM-1 of the
same Virtual Channel. The FARM-1 returns reports of the status of Transfer Frame
acceptance to the FOP-1 using the Communications Link Control Words (CLCWs).
NOTE – This Recommended Standard states that COP-1 handles ‘Transfer Frames’;
however, these are actually partial Transfer Frames made up of Frame Data Units
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