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Unformatted text preview: ggregating very small user messages into larger pieces and multiplexing
these pieces to provide responsive virtual access to the channel for all users.
A “TC Segment” is the specific form of the “TC Frame Data Unit” containing a Segment
B-2 TC SEGMENTATION LAYER SERVICE SPECIFICATION
The services provided by the Telecommand Segmentation layer are as follows:
(1) The layer breaks long user data structures from the layer above (i.e., TC Packets,
or other user data structures which have been generated by a non-standard higher
layer) into pieces (“TC Frame Data Units”) which will fit the data field of TC
Transfer Frames, and reassembles them after passage through the Transfer layer. (2) The layer optionally aggregates multiple TC Packets into a single TC Frame Data
Unit, which fits into the data field of a TC Transfer Frame and separates them
after passage through the Transfer layer. (3) The layer provides a mechanism for multiplexing different TC Frame Data Units
together onto a single Virtual Channel, for the purpose of flow control. The Segmentation service described in this Recommendation is designed to support the
standard CCSDS telecommand Packetization layer (Reference ). It can also provide CCSDS 202.0-B-2 Page B-2 CCSDS HISTORICAL DOCUMENT November 1992 CCSDS HISTORICAL DOCUMENT
CCSDS RECOMMENDATION FOR TELECOMMAND: DATA ROUTING SERVICE services to other non-standard higher-layer TC processes as long as the interface
requirements of the Segmentation layer are satisfied. SENDING
SINKS USER DATA UNITS DATA ROUTING SERVICE
BOUNDARY p 0 1 ••• n
(UP TO 64 PER
CHANNEL) n 1 0 ••• 1 SEGMENTATION
SENDING ENTITY p 1 0 ••• 0 SEGMENTATION
DATA UNIT ••• 0 1 2 3 4 TRANSFER
ENTITY m ••• VIRTUAL
(UP TO 64) m TC TRANSFER FRAME
CLCW IN TELEMETRY 4 3 2 1 0 TRANSFER
ENTITY COP Figure B-1: TC Data Routing Service Ele...
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This document was uploaded on 03/06/2014.
- Spring '14