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Header and Trailer

Header and Trailer

Standard Message Header

Each message is preceded by a standard header. The header identifies the message type, length, destination, sequence number, origination point and time.

Tag

FixName

Req

Valid Values

Data Type

Description

Tag

FixName

Req

Valid Values

Data Type

Description

8

BeginString

Y

FIXT1.1

String

Identifies beginning of new message and protocol version.
Always first field in message.
Always unencrypted.

9

BodyLength

Y

 

Int

Message length, in bytes, up to the CheckSum field.
Always second field in message.
Always unencrypted.
Maximum 500 Kbytes.

35

MsgType

Y

All msg types supported

String

Defines message type.
Always third field in message.

34

MsgSegNum

Y

 

Int

Message sequence number.

1128

AppVerID

N

9 = FIX50SP2

String

Indicates application version using a service pack identifier.

43

PossDupFlag

N

Y = Possible Duplicate
N = Original Transmission

Boolean

Indicates possible retransmission of message with this sequence number.
The value for this tag must be set to “Y” when messages are resent as a result of a resend request.

49

SenderCompID

Y

 

String

Assigned value used to identify firm sending the message.
All messages sent by your firm must have one SenderCompID that is agreed upon in advance with the Exchange.

52

SendingTime

Y

 

UTC Timestamp

Time of message transmission. (always expressed in UTC (Universal Time Coordinated, also known as “GMT”)

56

TargetCompID

Y

 

String (32)

Identifies the router receiving the message.
All messages sent by your firm to the exchange must have one TargetCompID.

97

PossResend

N

Y = Possible resend
N = Original transmission

Boolean

Indicates that the message may contain information that has been sent under another sequence number.

115

OnBehalfOfCompID

N

 

String(32)

A unique identifier assigned by the exchange to your firm.
This identifier must be present on all order related transactions as a means of identifying the originating source.

122

OrigSendingTime

N

 

UTC Timestamp

Required for messages resent as a result of a ResendRequest, including Gap Fill messages.
If data is not available, set to same value as SendingTime(52).

128

DeliverToCompID

N

 

String (32)

Identifies the target executing system.

116

OnBehalfOfSubID

N

 

String (32)

Value sent by the client that indicates the screen or user from which it originated.

129

DelliverToSubID

N

 

String (32)

Value sent by the client indicating the specific destination to which the message is sent.

 

Standard Message Trailer

Each message is terminated by a standard trailer.

Tag

FixName

Req

Valid Values

Data Type

Description

Tag

FixName

Req

Valid Values

Data Type

Description

10

CheckSum

Y

 

String(3)

Three byte, simple checksum.
Always last field in message.

Interconnection agreements between markets

The following tags are reserved for future use in routing scenarios involving more than two markets (eg. when a market sends orders to another via a third party):

  • OnbehalfOfCompID

  • DeliverToCompID

  • HopGrp

We repeat the values for SenderCompID and TargetCompID in the tags OnbehalfOfCompID and DeliverToCompID respectively.

 

Example header and trailer:

8=FIXT.1.1|9=61|35=0|34=17434|49=user_A|52=20250825-15:37:30.716|56=ROFX|10=175