Research how should CFDP work

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CCSDS documents:

• [BLUE BOOK] CCSDS FILE DELIVERY PROTOCOL (CFDP)
• [GREEN BOOK] PART 1: INTRODUCTION AND OVERVIEW
• [GREEN BOOK] PART 2: IMPLEMENTERS GUIDE
• [YELLOW BOOK] NOTEBOOK OF COMMON INTER-AGENCY TESTS FOR CORE PROCEDURES

We should support:

• Service classes
  • CLASS 1 (UNRELIABLE TRANSFER)
    • Without Transaction closure requested (should be possible via simplex transmission)
    • With Transaction closure requested (requires duplex transmission)
  • CLASS 2 (RELIABLE TRANSFER) (requires duplex transmission)
    • NACK modes (more info: [GREEN BOOK] PART 2: IMPLEMENTERS GUIDE 2.6.3.1)
      • Deferred
      • Immediate
      • Prompted
      • Asnychronous
  • CLASS 3 (UNRELIABLE TRANSFER VIA MULTIPLE WAYPOINTS)
  • CLASS 4 (RELIABLE TRANSFER VIA MULTIPLE WAYPOINTS)

New CFDP specification omits classes 3 and 4

• User operations
  • Proxy
    • Proxy Put Request
    • Proxy Message to User
    • Proxy Filestore Request
    • Proxy Fault Handler Override
    • Proxy Transmission Mode
    • Proxy Flow Label
    • Proxy Segmentation Control
    • Proxy Put Response
    • Proxy Filestore Response
    • Proxy Put Cancel
    • Proxy Closure Request
  • Remote status report
    • Remote Status Report Request
    • Remote Status Report Response
  • Directory
    • Directory Listing Request
    • Directory Listing Response
  • Remote suspend
    • Remote Suspend Request
    • Remote Suspend Response
  • Remote resume
    • Remote Resume Request
    • Remote Resume Response

User Operations refer to the use of the CFDP services offered by the local CFDP
entity to cause the CFDP user of a remote CFDP entity to initiate additional CFDP
transactions.

• Communication between CFDP User and its local enitity via primitives:
  

• Checksum algorithms:

  • Null (no checksum)
  • Modular checksum
  • In addition, we can implement others from the SANA Checksum Identifiers registry

• Transport

  • Layer(s)
    • UDP
    • Any type of TCP
  • Should we provide Space Packet implementation on top of transport layers?

• CFDP User
  

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There is also a set of timers and counters that should be implemented:

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The main part of communication between entities is Transaction. Transaction should be saved on both (receiver and sender) Entities with individual timers and counters. T has unique ID (4 bytes).

Should we preserve information about ongoing transaction between runs of the CFDP daemon?

One transaction can only transmit only one FDU (which can be empty -> only metadata FDU)

During a transaction, there are usually multiple PDUs that contain a piece of FDU or metadata.
There is 2 types of PDU:

• File Directive
  • EOF PDU
  • Finished PDU
  • ACK PDU
  • Metadata PDU
    • Can contains MessageToUser and Filestore requests
  • NAK PDU
  • Prompt PDU
  • Keep Alive PDU
• File Data

MessageToUser and Filestore requests have to been transmitted on the beginning of the transaction

IMPORTANT: MessageToUser requests should be send immediately to the Remote CFDP User via Metadata-Recv.indication but Filestore requests have to be sent only after all data transfer activities (if any)

Only one Metadata PDU can be send during transaction

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