Draft Recommendation for
Space Data System Standards
AOS SPACE DATA LINK PROTOCOL
DRAFT RECOMMENDED STANDARD CCSDS 732.0-P-2.1
PINK SHEETS
December 2008
DRAFT CCSDS RECOMMENDED STANDARD FOR AOS SPACE DATA LINK PROTOCOL
In accordance with standard data-communications practice, data fields are often grouped into eight-bit ‘words’ which conform to the above convention. Throughout this Recommendation, such an eight-bit word is called an ‘octet’.The numbering for octets within a data structure starts with zero. By CCSDS convention, all ‘spare’ bits shall be permanently t to ‘0’.
1.7REFERENCES
The following documents contain provisions which, through reference in this text, constitute provisions of this Recommendation. At the time of publication, the editions indicated were valid. All documents are subject to revision, and urs of this Recommendation are encouraged to investigate the possibility of applying the most recent editions of the documents indicated below. The CCSDS Secretariat maintains a register of currently valid CCSDS Recommendations.
[1] Information Technology—Open Systems Interconnection—Basic Reference Model:
The Basic Model. International Standard, ISO/IEC 7498-1. 2nd ed. Geneva: ISO, 1994.骆驼交配
[2] Information Technology—Open Systems Interconnection—Basic Reference Model—
Conventions for the Definition of OSI Services. International Standard, ISO/IEC 10731:1994. Gene
开展项目
va: ISO, 1994.
[3] TM Synchronization and Channel Coding. Recommendation for Space Data System
Standards, CCSDS 131.0-B-1. Blue Book. Issue 1. Washington, D.C.: CCSDS, September 2003.
[4] Space Link Identifiers. Recommendation for Space Data System Standards, CCSDS
135.0-B-3. Blue Book. Issue 3. Washington, D.C.: CCSDS, October 2006.
[5] CCSDS Global Spacecraft Identification Field Code Assignment Control Procedures.
Recommendation for Space Data System Standards, CCSDS 320.0-B-5. Blue Book.
Issue 5. Washington, D.C.: CCSDS, September 2007.
[6] Space Packet Protocol. Recommendation for Space Data System Standards, CCSDS
133.0-B-1. Blue Book. Issue 1. Washington, D.C.: CCSDS, September 2003.
answer什么意思[7] Encapsulation Service. Recommendation for Space Data System Standards, CCSDS
133.1-B-1. Blue Book. Issue 1. Washington, D.C.: CCSDS, June 2006.
粗粮早餐
NOTE – Informative references are listed in annex B.
DRAFT CCSDS RECOMMENDED STANDARD FOR AOS SPACE DATA LINK PROTOCOL
2.2.3 SUMMARY OF SERVICES
2.2.
3.1 Overview
Seven rvices are provided by the AOS Space Data Link Protocol. Five of them (Virtual Channel Packet, Bitstream, Virtual Channel Access, Virtual Channel Operational Control
Field, and Virtual Channel Frame) are provided for a Virtual Channel. One of them (Master
Channel Frame) is provided for a Master Channel. One of them (Inrt) is provided for all
Transfer Frames in a Physical Channel. Table 2-1 summarizes the rvices.
麦片馒头Table 2-1: Summary of Services Provided by AOS Space Data Link Protocol Service Service Type Service Data Unit
SAP Address Virtual Channel Packet (VCP)† Asynchronous Packet GVCID + Packet
Version Number
Bitstream Asynchronous or Periodic
Bitstream Data GVCID
Virtual Channel Access
(VCA) Asynchronous or
Periodic
VCA_SDU GVCID
Virtual Channel Operational Control Field (VC_OCF)
经济合同
Synchronous or Periodic
OCF_SDU GVCID
Virtual Channel Frame (VCF) Asynchronous or Periodic Transfer Frame
GVCID
鲨肝醇片Master Channel Frame (MCF) Asynchronous or Periodic Transfer Frame
MCID
Inrt Periodic IN_SDU Physical Channel
Name
† The term ‘Packet Service’ is ud as an abbreviation for Virtual Channel Packet (VCP) Service.
2.2.
3.2 Virtual Channel Packet (VCP) Service
The Virtual Channel Packet (VCP) Service transfers a quence of variable-length, delimited,
octet-aligned rvice data units known as Packets across a space link. The Packets
transferred by this rvice must have a Packet Version Number (PVN) authorized by
CCSDS. For the Packet Version Numbers prently authorized by CCSDS, e reference [4].
2.2.
3.8Inrt Service
The Inrt Service provides transfer of private, fixed-length, octet-aligned rvice data units across a
space link in a mode which efficiently utilizes the space link transmission resources at relatively low data rates. The rvice is unidirectional, periodic, and quence-prerving. The rvice does not guarantee completeness, but may signal gaps in the quence of rvice data units delivered to a receiving ur.
For a given rvice instance, only one ur, identified with the Physical Channel Name of the Physical Channel, can u this rvice on a Physical Channel. Service data units from different urs are not multiplexed together within one Physical Channel.
2.2.4RESTRICTIONS ON SERVICES
There are some restrictions on the rvices provided on a Physical Channel, as follows:
a)On one Physical Channel, the Inrt rvice shall not exist simultaneously with the
Virtual Channel Frame or Master Channel Frame rvice.
b)If the Master Channel Frame Service exists on a Master Channel, other rvices shall
not exist simultaneously on that Master Channel.
c)If the Virtual Channel Frame Service exists on a Virtual Channel, other rvices shall
not exist simultaneously on that Virtual Channel.
d)On a Virtual Channel on which the Virtual Channel Frame Service does not exist,
only one of the Virtual Channel Packet Service, the Bitstream Service, or the Virtual Channel Access Service shall exist simultaneously.
2.3OVERVIEW OF FUNCTIONS
2.3.1GENERAL FUNCTIONS
The AOS Space Data Link Protocol transfers various rvice data units supplied by nding urs encapsulated in a quence of protocol data units using rvices of lower layers. The protocol data units, known as AOS Transfer Frames, have a fixed length and must be transferred over a Physical Channel at a constant rate.
The protocol entity performs the following protocol functions:
a)generation and processing of protocol control information (i.e., headers and trailers)
to perform data identification, loss detection, and error detection;
b)gmenting and blocking of rvice data units to transfer variable-length rvice data
units in fixed-length protocol data units;
c)multiplexing/demultiplexing and commutation/decommutation in order for various
rvice urs to share a single Physical Channel;
3SERVICE DEFINITION
3.1OVERVIEW
This ction provides rvice definition in the form of primitives, which prent an abstract model of the logical exchange of data and control information between the protocol entity and the rvice ur. The definitions of primitives are independent of specific implementation approaches.
The parameters of the primitives are specified in an abstract n and specify the information to be
made available to the ur of the primitives. The way in which a specific implementation makes this information available is not constrained by this specification. In addition to the parameters specified in this ction, an implementation may provide other parameters to the rvice ur (e.g., parameters for controlling the rvice, monitoring performance, facilitating diagnosis, and so on).
3.2SOURCE DATA
3.2.1SOURCE DATA OVERVIEW
NOTE – This subction describes the rvice data units that are transferred from nding urs to receiving urs by the AOS Space Data Link Protocol.
The rvice data units transferred by the AOS Space Data Link Protocol shall be:
a)Packet;
b)Bitstream Data;
西游记第九回主要内容c)Virtual Channel Access Service Data Unit (VCA_SDU);
d)Operational Control Field Service Data Unit (OCF_SDU);
e)AOS Transfer Frame;
f)Inrt Service Data Unit (IN_SDU).
3.2.2PACKET
3.2.2.1Packets shall be transferred over a space link with the Virtual Channel Packet Service.
3.2.2.2The Packets transferred by this rvice must have a Packet Version Number (PVN) authorized by CCSDS.
3.2.2.3The position and length of the Packet Length Field of the Packets must be known to the rvice provider in order to extract Packets from Transfer Frames at the receiving end.
