1 of this recommendation the length of any transfer

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Unformatted text preview: The length of any Transfer Frame transferred on a Physical Channel must be the same, and is established by management. 3.3 PACKET SERVICE 3.3.1 OVERVIEW OF PACKET SERVICE The Packet Service transfers a sequence of variable-length, delimited, octet-aligned service data units known as Packets across a space link. The Packets transferred by this service must have a Packet Version Number (PVN) authorized by CCSDS. For the Packet Version Numbers presently authorized by CCSDS, see reference [4]. The service is unidirectional, asynchronous and sequence-preserving. It does not guarantee completeness, nor does it signal gaps in the sequence of service data units delivered to a receiving user. CCSDS 132.0-B-1 Page 3-3 September 2003 CCSDS RECOMMENDATION FOR TM SPACE DATA LINK PROTOCOL A user of this service is a protocol entity that sends or receives Packets with a single PVN. A user is identified with the PVN and a GVCID. Different users (i.e., Packets with different versions) can share a single Virtual Channel, and if there are multiple users on a Virtual Channel, the service provider multiplexes Packets of different versions to form a single stream of Packets to be transferred on that Virtual Channel. 3.3.2 PACKET SERVICE PARAMETERS 3.3.2.1 General The parameters used by the Packet Service primitives shall conform to the specifications contained in subsections 3.3.2.2 through 3.3.2.5. 3.3.2.2 Packet The Packet parameter shall contain a Packet for transfer by the Packet Service. NOTE – The Packet parameter is the service data unit transferred by the Packet Service. For restrictions on the Packets transferred by the Packet Service, see 3.2.2. 3.3.2.3 GVCID The GVCID parameter shall contain a GVCID that indicates the Virtual Channel through which the Packet is to be transferred. NOTE – The GVCID parameter is part of the SAP address of the Packet Service. 3.3.2.4 Packet Version Number NOTE – The Packet Version Number parameter is part of the SAP address of the Packet Service and identifies the protocol entity of the upper layer that uses the Packet Service. 3.3.2.5 Packet Quality Indicat...
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