final version of ASN.1 code

    minor-version-1(1)}

    DEFINITIONS AUTOMATIC TAGS ::= BEGIN

------------------------------------------

-- Specification of the segment message format to be used for the segmentation service

-- Specification of the segment message format to be used for the segmentation service.

-- Different segmentation methods are supported. One method consists in splitting the original file or message into several 

-- sequential segments (called sequential chunks). This specification can be extended to integrate transport coding methods

-- using various FEC schemes.

------------------------------------------

IMPORTS 

    HashedId8,

    Opaque,

    Psid,

    Time64,

    Uint8 FROM Ieee1609Dot2BaseTypes {iso(1) identified-organization(3) ieee(111)

    Time32,

    Uint8

FROM Ieee1609Dot2BaseTypes {iso(1) identified-organization(3) ieee(111)

    standards-association-numbered-series-standards(2) wave-stds(1609) dot2(2)

    base(1) base-types(2) major-version-2(2) minor-version-4(4)}

WITH SUCCESSORS

* @field version: contains the version number of this PDU definition. For this version of this data type it shall be equal to `1`.

* 

* @field segmentationTime: contains information on when the message or file was segmented into 1 or several pieces.

* So the segmentationTime of all the segments for this message or file shall be the same.

*

* - not included in the present version @field segmentationLocation: is the location at which the message or file was segmented

* @field distributedAid:  the ITS-AID of the file. The Psid/ Its-AID is a variable length INTEGER number.

* 

* @field fileId: the id of the file to be distributed. It shall be set to the output of the SHA-256 hash function calculated on the transmitted CTL or file content.

* 

* @field fileDescription: the file description or metadata of the segmented file. 

* For instance, metadata could contain parameters required when coding scheme using a FEC encoding is used (cf. IETF RFC 6726)

* In the current version of this standard, the fileDescription shall be of 0 byte length.

*

* @field segmentContent : contains the segmented data of the message or file. 

*/

SegmentPDU ::= SEQUENCE {

SegmentPDU {Psid} ::= SEQUENCE {

    version           Uint8,

    segmentationTime       Time64,

    segmentContent	SegmentedData {Psid}

    segmentationTime  Time32,

    distributedAid    Psid,

    fileId            HashedId8,

    fileDescription   OCTET STRING (SIZE(0..63)),

    segmentContent	  SegmentedData

}   

/**

* This component represents the payload of a segment/fragment of the file data. 

*/

SegmentedData ::= CHOICE {  

    seqChunks SequentialChunksSegmentedData,

    ...

}  

/**

* This component represents the payload of a segment/fragment of the file data when the sequential 

* segmentation method is used.  This method is applied in case the fileDescription is set to value 'FF'.

* It is composed of the following fields:

* @field distributedAid:  the ITS-AID of the file. The Psid/ Its-AID is a variable length INTEGER number.

* In the present version, the length of Its-AID will be less than or equal to 2 bytes. 

* 

* @field fileId: the id of the file to be distributed. It shall be set to the output of the SHA-256 hash function calculated on the transmitted CTL file content.

* 

* @field fileDescription: optionally, the file description or metadata of the segmented file.

* For instance, metadata could contain parameters required when coding scheme using a FEC encoding is used (cf. IETF RFC 6726)

*

* @field messageSegmentTotalNumber: the total number of segments/fragments constituting the complete file. 

*

* @field thisMessageSegmentNumber: the number that indicates the rank or position of this segment in the ordered sequence of segments constituting the complete CTL.

*

* The fields messageSegmentTotalNumber and thisMessageSegmentNumber may be present or absent depending on the use of a network/transport

* coding technique. If network/transport coding is used, these fields are unused and shall be absent.

* Note that coding technique is not specified in the current version of the standard.

* MAX value is equal to the maximum size of the payload contained in the Segment PDU, i.e. the MTU-GN - control fields size. MTU value depends

* on the network access technology and on the network layer. For instance, if ITS-G5 access layer

* and GeoNetworking SHB protocol is used, MTU-GN - GN-Header - BTP-Header = 1428 bytes and MAX value is calculated as:

* 1428  - control fields size (30 bytes restricting the ITS-AID size to a maximum of 2 bytes). 

* 1428  - control fields size. 

*

* All segments of the original full CTL, except the last one, shall have the same size equal to MAX value.

* All the segments, but the last one, of the original file (e.g. the full CTL) shall have the same size equal to MAX value .

*/

SegmentedData {Psid}::= SEQUENCE {

    distributedAid          Psid,          

    fileId          HashedId8,     

    fileDescription   OCTET STRING (SIZE (5)) OPTIONAL,

    messageSegmentTotalNumber	INTEGER(1..255) OPTIONAL,

    thisMessageSegmentNumber	INTEGER(1..255) OPTIONAL,

    data         OCTET STRING (SIZE(1..MAX)),

...

SequentialChunksSegmentedData ::= SEQUENCE {

    messageSegmentTotalNumber	INTEGER(1..255),

    thisMessageSegmentNumber	INTEGER(1..255),

    data                        OCTET STRING (SIZE(1..MAX))

}

/**

* The Segmented CTL Responsemessage (SCRM) is a specific Segment PDU: it uses the parametrized data type SegmentedData where the psid parameter value is set to 

* the ITS-AID value of the CTL service as specified in ETSI TS 102 965 (i.e. value 624)

* The Segmented CTL Responsemessage (SCRM) is a specific Segment PDU: it uses the parametrized data type 

* SegmentedData where the psid parameter value is set to the ITS-AID value of the CTL service as specified in 

* ETSI TS 102 965 (i.e. value 624). For the SCRM message, the size of the control information (“header” fields) is 23 bytes.

*/

ctlPsid Psid ::= 624

ScrmData ::= SegmentedData {Psid (ctlPsid)}

ScrmPDU ::= SegmentPDU {Psid (ctlPsid)}

END

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