Logon (MsgType = A)

The logon message authenticates a user establishing a connection to a remote system. The logon message must be the first message sent by the application requesting to initiate a FIX session.

The HeartBtInt (108) (108) field is used to declare the timeout interval for generating heartbeats (same value used by both sides). The HeartBtInt (108) value should be agreed upon by the two firms and specified by the Logon (A) initiator and echoed back by the Logon (A) acceptor.

Upon receipt of a Logon (A) message, the session acceptor will authenticate the party requesting connection and issue a Logon (A) message as acknowledgment that the connection request has been accepted. The acknowledgment Logon (A) can also be used by the initiator to validate that the connection was established with the correct party.

The session acceptor must be prepared to immediately begin processing messages after receipt of the Logon. The session initiator can choose to begin transmission of FIX messages before receipt of the confirmation Logon, however it is recommended that normal message delivery wait until after the return Logon (A) is received to accommodate encryption key negotiation.

The confirmation Logon (A) can be used for encryption key negotiation. If a session key is deemed to be weak, a stronger session key can be suggested by returning a Logon (A) message with a new key. This is only valid for encryption protocols that allow for key negotiation. (See the FIX Web Site's Application notes for more information on a method for encryption and key passing.)

The Logon (A) message can be used to specify the MaxMessageSize (383) supported (i.e. can be used to control fragmentation rules for very large messages which support fragmentation). It can also be used to specify the MsgTypes supported for both sending and receiving.

Tag		Field Name	Req'd	Comments
<Standard Message Header>			Y	MsgType = A
98		EncryptMethod	Y	(Always unencrypted)
108		HeartBtInt	Y	Note same value used by both sides
95		RawDataLength	C	Required for some authentication methods
96		RawData	C	Required for some authentication methods
141		ResetSeqNumFlag	N	Indicates both sides of a FIX session should reset sequence numbers
789		NextExpectedMsgSeqNum	N	Optional, alternative via counterparty bi-lateral agreement message gap detection and recovery approach (see "Logon Message NextExpectedMsgSeqNum (789) Processing" section)
383		MaxMessageSize	N	Can be used to specify the maximum number of bytes supported for messages received
384		NoMsgTypes	N	Specifies the number of repeating RefMsgTypes specified
=>	372	RefMsgType	C	Specifies a specific, supported MsgType. Required if NoMsgTypes (384) is > 0. Should be specified from the point of view of the sender of the Logon (A) message
=>	385	MsgDirection	C	Indicates direction (send vs. receive) of a supported MsgType. Required if NoMsgTypes (384) is > 0. Should be specified from the point of view of the sender of the Logon (A) message
=>	1130	RefApplVerID	N	Specifies the service pack release being applied to a message at the session level. Enumerated field with values assigned at time of service pack release
=>	1406	RefApplExtID	N	Specified the extension pack being applied to a message
=>	1131	RefCstmApplVerID	N	Specifies a custom extension to a message being applied at the session level.
=>	1410	DefaultVerIndicator	N	Indicates that this Application Version (RefApplVerID(1130), RefApplExtID(1406),RefCstmApplVerID(1131)) is the default for the RefMsgType(372) field
464		TestMessageIndicator	N	Can be used to specify that this FIX session will be sending and receiving "test" vs. "production" messages.
553		Username	N
554		Password	N	Note: minimal security exists without transport-level encryption.
925		NewPassword	N	Specifies a new password for the FIX Logon. The new password is used for subsequent logons.
1400		EncryptedPasswordMethod	N
1401		EncryptedPasswordLen	N
1402		EncryptedPassword	N
1403		EncryptedNewPasswordLen	N
1404		EncryptedNewPassword	N	Encrypted new password- encrypted via the method specified in the field EncryptedPasswordMethod(1400)
1409		SessionStatus	N	Session status at time of logon. Field is intended to be used when the logon is sent as an acknowledgement from acceptor of the FIX session.
1137		DefaultApplVerID	Y	The default version of FIX being carried over this FIXT session
1407		DefaultApplExtID	N	The default extension pack for FIX messages used in this session
1408		DefaultCstmApplVerID	N	The default custom application version (dictionary) for FIX messages used in this session
58		Text	N	Available to provide a response to logon when used as a logon acknowledgement from acceptor back to the logon initiator.
354		EncodedTextLen	N	Must be set if EncodedText field is specified and must immediately precede it.
355		EncodedText	N	Encoded (non-ASCII characters) representation of the Text field in the encoded format specified via the MessageEncoding field.
<Standard Message Trailer>			Y

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