Documentation update

# <a name="EtsiTs103601Module"></a>ASN.1 module EtsiTs103601Module

OID: _{itu-t(0) identified-organization(4) etsi(0) itsDomain(5) wg5(5) ts(103601) p2pctlresponse(1) major-version-1(1) minor-version-1(1)}_

## Imports:

* **[Ieee1609Dot2BaseTypes](Ieee1609Dot2BaseTypes.md)** *{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*<br/>

## Data Elements:

### <a name="SegmentPDU"></a>SegmentPDU

This component is the general PDU generated by the segmentation service to transmit a segment of a large message or file.

 It shall include the following components:

* _version_ of type [**Uint8**](Ieee1609Dot2BaseTypes.md#Uint8) <br>

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

* _segmentationTime_ of type [**Time64**](Ieee1609Dot2BaseTypes.md#Time64) <br>

  contains information on when the message or file was segmented into 1 or several pieces.

* segmentContent<br>

  contains the segmented data of the message or file. 

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

```asn1

SegmentPDU ::= SEQUENCE {

    version              Uint8,

    segmentationTime       Time64,

    segmentContent	SegmentedData {Psid}

}

```

### <a name="SegmentedData"></a>SegmentedData

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

 It is composed of the following fields:

* _distributedAid_ of type [**Psid**](Ieee1609Dot2BaseTypes.md#Psid) <br>

  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. 

* _fileId_ of type [**HashedId8**](Ieee1609Dot2BaseTypes.md#HashedId8) <br>

  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.

* _fileDescription_ of type **OCTET STRING**  (SIZE (5)) OPTIONAL<br>

  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)

* _messageSegmentTotalNumber_ of type **INTEGER** (1..255) OPTIONAL<br>

  the total number of segments/fragments constituting the complete file. 

* _thisMessageSegmentNumber_ of type **INTEGER** (1..255) OPTIONAL<br>

  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.

* _data_ of type **OCTET STRING**  (SIZE(1..MAX))<br>

  this field represents the file segment/fragment payload.

   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). 

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

```asn1

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)),

...

}

```

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)

```asn1

ctlPsid Psid ::= 624

```

### <a name="ScrmData"></a>ScrmData

Values:

* **Psid** (ctlPsid)<br>

```asn1

ScrmData ::= SegmentedData {Psid (ctlPsid)}

```