202x0b2sRouting Svc

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Unformatted text preview: ch portion, 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 CCSDS 202.0-B-2 Page 3-4 CCSDS HISTORICAL DOCUMENT November 1992 CCSDS HISTORICAL DOCUMENT CCSDS RECOMMENDATION FOR TELECOMMAND: DATA ROUTING SERVICE (4) Multiplexes together the TC Frame Data Units from one group of up to 64 MAPs onto one Virtual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 FOLLOWING: (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.

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