Standard Header from Client System to CME STP

Tag	Name	Req	Format	Description	Enumerations
8	BeginString	Y	String	Identifies beginning of new message and protocol version. Always unencrypted, must be first field in message.	FIX.4.4
9	BodyLength	Y	Length	Message length, in bytes, forward to the CheckSum field. Always unencrypted, must be second field in message.
35	MsgType	Y	String	Defines message type. Always unencrypted, must be third field in message.
49	SenderCompID	Y	String	Assigned value as defined by CME Group used to identify firm sending message. Always unencrypted.
50	SenderSubID	N	String	Optional Client Assigned value used to identify specific message originator (user) within a firm. If populated in Logon message, same value must be populated in subsequent messages from client to CME STP. CME STP will populate this value in 57-TargetSubID on messages routed to the client.
56	TargetCompID	Y	String	Assigned value used to identify receiving firm. Format: ‘CMESTPFIX#’ The value will be incremented for each new user at the Firm, e.g., CMESTPFIX1, CMESTPFIX2, CMESTPFIX3, etc. Always unencrypted.
57	TargetSubID	N	String	If populated in Logon message, Only acceptable value is "STP" and same value need to be populated in subsequent messages from client to CME STP. CME STP will populate this value in 50-SenderSubID on messages routed to the client. Always unencrypted.
34	MsgSeqNum	Y	SeqNum	Integer message sequence number.
43	PossDupFlag	N	Boolean	Indicates possible retransmission of message with this sequence number. Required for retransmitted messages.	‘Y’ (Possible duplicate) 'N' (Original transmission)
97	PossResend	N	Boolean	Indicates that message may contain information that has been sent under another sequence number.	‘Y’ (Possible resend) ‘N’ (Original transmission)
52	SendingTime	Y	UTCTimestamp	Time of message transmission (expressed in UTC). YYYYMMDD-HH:MM:SS.sss Can be embedded within encrypted data section. UTC Timestamps are sent in number of nanoseconds since Unix epoch synced to a master clock to microsecond accuracy.
122	OrigSendingTime	N	UTCTimestamp	Original time of message transmission when transmitting messages as the result of resend request (expressed in UTC). UTC Timestamps are sent in number of nanoseconds since Unix epoch synced to a master clock to microsecond accuracy. Required for message resent as a result of a resend request.