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** Conformance / Proximity-1 Data Link Layer * PAGE 11 / 23

** Astro * Conformance

** /conformance/pxdl

Proximity-1 Data Link Layer

PICS proforma: what this package implements, clause by clause.

Conformance Statement for `pkg/pxdl`, CCSDS 211.0-B-6

A1.1 GENERAL INFORMATION

A1.1.1 Identification of PICS

Field	Value
Date of Statement (DD/MM/YYYY)	23/08/2026
PICS Serial Number	ASTRO-PXDL-PICS-001
System Conformance Statement Cross-Reference	This document

A1.1.2 Identification of Implementation Under Test (IUT)

Field	Value
Implementation Name	astro/pkg/pxdl
Implementation Version	See `go.mod` / latest commit on `main`
Special Configuration	`Reassembler.MaxPacketSize` bounds an accumulating packet
Other Information	Go library implementing the Version-3 Transfer Frame, its data field constructions, packet segmentation and reassembly keyed on routing ID, and both supervisory PDU formats including the Proximity Link Control Word.

A1.1.3 Identification of Supplier

Field	Value
Supplier	Ravi Suhag
Contact Point for Queries	GitHub, github.com/ravisuhag/astro
Implementation Name(s) and Version(s)	astro/pkg/pxdl (Go package)
System Name(s)	Astro

A1.1.4 Identification of Specification

Field	Value
Specification	CCSDS 211.0-B-6 (Proximity-1 Space Link Protocol, Data Link Layer, Blue Book, Issue 6, July 2020)
Have any exceptions been required?	Yes [X] No [ ], see A1.6

A1.2 TRANSFER FRAME

Feature	Reference	Status	Support
Version-3 Transfer Frame structure	clause 3.2.1	M	Y: 5-octet header, up to 2043 octets of data
Transfer Frame Version Number = binary '10'	clause 3.2.2.2.2	M	Y: other values rejected on decode
Quality of Service Indicator	clause 3.2.2.3	M	Y: sequence controlled and expedited
PDU Type ID: U-frame and P-frame	clause 3.2.2.4	M	Y
Data Field Construction ID	clause 3.2.2.5	M	Y: all four values of table 3-1
DFC ID zero in a P-frame	clause 3.2.2.5.2	M	Y: enforced
Spacecraft Identifier, 10 bits	clause 3.2.2.6	M	Y
Physical Channel Identifier	clause 3.2.2.7	M	Y
Port Identifier, 3 bits	clause 3.2.2.8	M	Y
Port ID zero in a P-frame	clause 3.2.2.8.2	M	Y: enforced
Source-or-Destination Identifier	clause 3.2.2.9	M	Y: '0' = source, '1' = destination, per table 3-2
Frame Length as a count less one	clause 3.2.2.10.2	M	Y: 5 to 2048 octets enforced
Frame Sequence Number	clause 3.2.2.11	M	Y: carried; COP-P is out of scope

A1.3 DATA FIELD CONSTRUCTIONS

Feature	Reference	Status	Support
Packets, DFC ID '00'	clause 3.2.3.2	O	Y: carried verbatim
Segment data units, DFC ID '01'	clause 3.2.3.3	O	Y
Segment header: sequence flags and pseudo packet ID	clause 3.2.3.3.2	M	Y
Sequence flag values of table 3-4	clause 3.2.3.3.2 a)	M	Y
Reassembly by routing ID	clause 3.2.3.3.3	M	Y: PCID, Port ID and pseudo packet ID
Only complete packets delivered	clause 3.2.3.3.4	M	Y
Discard on a segment before the start segment	clause 3.2.3.3.5 b)	M	Y: `ErrSegmentOutOfOrder`
User defined data, DFC ID '11'	clause 3.2.3.5	O	Y: carried verbatim

A1.4 SUPERVISORY PDUs

Feature	Reference	Status	Support
Fixed-length SPDU format	clause 3.2.4.2.1	M	Y: 2 octets
Variable-length SPDU format	clause 3.2.4.2.2	M	Y: 1 octet header, 0 to 15 octets of data
Data field length is the actual count	clause 3.2.4.2.2 a) 3) note	M	Y
SPDUs are self-delimiting	clause 3.2.4.1	M	Y: a mixed run decodes without a count
SPDUs only on the Expedited service	clause 3.2.4.1	M	Y: enforced by the constructor
Type F1: Proximity Link Control Word	clause 3.2.4.3.2	M	Y
PLCW field layout of figure 3-5	clause 3.2.4.3.2.1.1	M	Y: all seven fields, verified against the published figure
PLCW Report Value = V(R)	clause 3.2.4.3.2.2.2	M	Y
Type F2 fixed-length SPDU	table 3-5	-	N: reserved for future CCSDS use

A1.5 MANAGED PARAMETERS

Feature	Reference	Status	Support
Managed parameter representation	clause 4, annex C	M	P: `ManagedParameters` holds the frame-layer subset
Local_Spacecraft_ID, Remote_Spacecraft_ID	annex C	M	Y
Maximum_Frame_Length, per direction	annex C	M	Y: send and receive maxima held separately
Maximum_Packet_Size	clause 4.4.2.1	M	Y
Synch_Timeout, PLCW_Repeat_Interval	annex C	M	Y: carried; nothing in this package acts on timers
MAC, hailing, and COP-P parameters	annex C	M	N: out of scope with those sublayers, see A1.6

A1.6 EXCEPTIONS AND UNSUPPORTED FEATURES

Feature	Reference	Support	Rationale
COP-P retransmission procedure	clause 7	N	Sequence numbers and PLCWs are carried; the state machine that acts on them is a follow-up, modelled on `pkg/cop`.
Directive and status report contents	annex B	P	Variable-length SPDUs encode and decode; their payloads are carried without interpretation.
MAC sublayer, session establishment	clause 5, clause 6	N	Out of scope for the frame layer.
Physical layer, transceiver control	CCSDS 211.1-B	N	A separate specification.
Coding and synchronization	CCSDS 211.2-B-3	N	A separate specification; `pkg/pxsc`.
CLI subcommands	-	N	A follow-up once the API settles.

A1.7 IMPLEMENTATION LIMITS

Limit	Value	Source
Transfer Frame length	5 to 2048 octets	11-bit length field, clause 3.2.2.10.2
Transfer Frame Data field	2043 octets	clause 3.2.1 b)
Spacecraft Identifier	0 to 1023	10-bit field, clause 3.2.2.6.1
Port Identifier	0 to 7	3-bit field, clause 3.2.2.8
Pseudo packet identifier	0 to 63	6-bit field, clause 3.2.3.3.2 b)
Variable-length SPDU data	0 to 15 octets	4-bit length field, clause 3.2.4.2.2
Reassembled packet	`MaxPacketSize`, default 64 KiB	Implementation choice; the standard sets no ceiling