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forming the TC Segment/Frame Data Unit. If the TC User Data Unit is a TC
Packet, the first octet of the TC Packet Primary Header shall appear in the leading
octet of the first corresponding Segment Data Field. The first and continuing
Segments may each have a length equal to the maximum allowable length of the
TC Frame Data Unit on that particular Virtual Channel. The last Segment shall
have a length equal to the residue of the TC User Data Unit plus the Segmentation
Header. (3) If aggregation is permitted on a particular MAP, the Segmentation layer places
complete TC packets into the TC Segment in the order of arrival. If Segment
Headers (and hence MAPs) are not used on a particular Virtual Channel, but
aggregation is permitted, the Segmentation layer places the TC Packets directly
into the TC Frame Data Unit. In either case, the aggregated packets (plus
Segment Header, if used) must fit within the maximum size TC Frame Data Unit
permitted for the Virtual Channel. The limitations on the number of MAPs which
can be aggregating TC Packets simultaneously and mechanisms for ensuring
transmission of all TC Packets are implementation dependent. CCSDS 202.0-B-2 Page 3-4 CCSDS HISTORICAL DOCUMENT November 1992 CCSDS HISTORICAL DOCUMENT
CCSDS RECOMMENDATION FOR TELECOMMAND: DATA ROUTING SERVICE (4) Multiplexes together the TC Frame Data Units from one group of up to 64 MAPs
onto one Virtual Channel, according to the mission’s priority scheme, and passes
the multiplexed stream to the layer below.
CAUTION A TC FRAME DATA UNIT SHALL CONSIST OF ONLY ONE OF THE
(a) A TC SEGMENT CONTAINING A PORTION OF ONE TC USER DATA
UNIT (E.G. A PORTION OF ONE TC PACKET); or (b) A TC SEGMENT CONTAINING ONE COMPLETE TC USER DATA
UNIT(E.G., ONE COMPLETE TC PACKET); or (c) A TC SEGMENT CONTAINING MULTIPLE COMPLETE TC PACKETS;
or (d) ONE COMPLETE TC USER DATA UNIT (E.G., ONE COMPLETE TC
PACKET); or (e) MULTIPLE COMPLETE TC PACKETS. TC Packets and user-defined data units may not be intermixed. Each MAP (if Segment
Headers are used) or Virtual Channel (if Segment Headers are not used) shall carry either TC
Packets or user...
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This document was uploaded on 03/06/2014.
- Spring '14