Unformatted text preview: horized by CCSDS, see reference . 3.2.3 VIRTUAL CHANNEL ACCESS SERVICE DATA UNIT (VCA_SDU)
VCA_SDUs shall be transferred over a space link with the Virtual Channel Access Service.
NOTE – Virtual Channel Access Service Data Units (VCA_SDUs) are fixed-length, octetaligned data units, the format of which is unknown to the service provider. Their
length is established by management.
3.2.4 FRAME SECONDARY HEADER SERVICE DATA UNIT (FSH_SDU)
188.8.131.52 Frame Secondary Header Service Data Units (FSH_SDUs) shall be transferred over
a space link with the VC_FSH or MC_FSH Service. Data units may be carried in every
frame of a Virtual Channel, using the VC_FSH Service, or, in every frame of a Master
Channel, using the MC_FSH Service.
184.108.40.206 Although the transfer of FSH_SDUs is synchronized with the Virtual Channel or
Master Channel that will provide the transfer service, the creation of FSH_SDUs by the
sending user may or may not be synchronized with the Virtual Channel or Master Channel.
Such synchronization, if required for timing or other purposes, is a mission-design issue.
NOTE – Frame Secondary Header Service Data Units (FSH_SDUs) are fixed-length data
units carried in the Transfer Frame Secondary Header (FSH), defined in 4.1.3,
from a sending end to a receiving end. Their length may be of any constant value
which is an integral number of octets, between 2 octets and 64 octets. It shall be
static within the associated Master or Virtual Channel, and is established by
management. Except for the Frame Secondary Header Identification Field
defined in 220.127.116.11, CCSDS specifies no format or semantics for the content of an
3.2.5 OPERATIONAL CONTROL FIELD SERVICE DATA UNIT (OCF_SDU)
18.104.22.168 Operational Control Field Service Data Units (OCF_SDUs) shall be transferred
over a space link with the VC_OCF or MC_OCF Service. Data units may be carried in every
frame of a Virtual Channel, using the VC_OCF Service, or, in every frame of a Master
Channel, using the MC_OCF Service.
22.214.171.124 Although the tran...
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- Space Exploration, European Space Agency, Protocol data unit