Unformatted text preview: orward Space Packet Protocol Service (reference ) is used on the ground to
forward Space Packets (reference ) to be transmitted to a spacecraft using the TC-SDLP,
the algorithm specified in reference  must be used for multiplexing Virtual Channels and
MAP Channels. Otherwise, CCSDS does not recommend any standard algorithm for
multiplexing MAP or Virtual Channels, and it is the responsibility of the project to ensure
that the multiplexing algorithm used for that project actually satisfies the requirements.
3.2.4 TRANSFER TIMING 126.96.36.199 General The timing at which SDUs supplied by the sending users are transferred over the space link
and delivered to the receiving users differs depending on the protocol and the service.
188.8.131.52 Transfer Timing of TC-SDLP The TC Space Data Link Protocol does not specify any rules for the timing of the transfer of
SDUs supplied by the sending user. The user may submit SDUs at any time, but the timing
of actual data transfer is determined by the service provider in accordance with missionspecific rules (such as multiplexing algorithms or scheduled release times) and may depend
on the data traffic at the time of transfer.
184.108.40.206.1 Transfer Timing of TM-SDLP and AOS-SDLP
General The TM and AOS Space Data Link Protocols have three service types (asynchronous,
synchronous, and periodic) that determine the timing at which SDUs supplied by the sending
user are transferred over the space link.
220.127.116.11.2 Asynchronous Service In asynchronous service, there are no timing relationships between the submission of SDUs
by the service user and their transfer by the service provider over the space link. The sending
user may request data transfer at any time, but the timing of actual data transfer is determined
by the service provider in accordance with mission-specific rules (such as multiplexing
algorithms) and may depend on the data traffic at the time of transfer. CCSDS 130.2-G-1 Page 3-4 December 2007 CCSDS REPORT CONCERNING THE SPACE DATA LINK PROTOCOLS Receiving
User Queue Space Data Link Protocol
(Service Provider) Figure 3-2: Asynchronous Service Model
In this service type (figure 3-2), each SDU from a sending user is placed in a queue, the
contents of which are sent to a receiving user in the order in which they were presented.
Although transmission errors may prevent delivery of some SDUs, the service provider
attempts to transfer all SDUs provided by the sending user exactly once. The key feature of
this service type is that all of the SDUs from the sending user are transferred, and transferred
18.104.22.168.3 Synchronous Service In synchronous service, the transfer of SDUs is synchronized with the release by the service
provider of Transfer Frames associated with the service. The transfer timing may be periodic
In this service (figure 3-3), each SDU from a sending user is placed in a buffer that can hold
only one SDU; the content of the buffer is sent to a receiving user at the time when a Sending
User Buffer Receiving
User Space Data Link Protocol
(Service Provider) Figure 3-3: Synchronous Service Model CCSDS 130.2-G-1 Page 3-5 December 2007 CCSDS REPOR...
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