Message protocol

Every <<glossary:FAST>> message contains an ISO-8583 message in one node. The other nodes (specific to <<glossary:Banking.Live>>) give additional context to a particular transaction.

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For a description of the data element (DE) fields in ISO-based messages, we recommend that you refer to the specification relevant to your card scheme.

ISO-8583 standard

ISO-8583 is an international standard for financial transaction card-originated interchange messaging. It is the International Organization for Standardization standard for systems that exchange electronic transactions initiated by cardholders using payment cards.

For more details, you can read more general information on ISO-8583.

Message Type Identifier (MTI / MTID)

Message Type Identifier is a key element which classifies the function of the ISO message. MTI is a 4-digit-long field, and each of the digits has its own meaning:

More details about the columns:

ISO-8583 version

There are a few versions of the ISO 8583 standard:

• ISO-8583:1987
• ISO-8583:1993
• ISO-8583:2003

1987 and 1993 versions are very similar, and version 2003 is very different and was created to be more generic.

Message class

Message function

Message origin

Commonly used MTIs

Below are the commonly used Message Type Identifiers (MTIs) in <<glossary:Banking.Live>> FAST messages.

FAST message structure

Here we define the format and content of all messages that may be exchanged through the <<glossary:Banking.Live>> <<glossary:FAST>> Interface.

The JSON structure sent by <<glossary:Banking.Live>> contains the results of the assessment of the Authorisation/Settlement transaction request, together with the ISO structure set by the relevant card scheme (Visa, Mastercard or Union Pay) and <<glossary:Banking.Live>>'s Rules Engine result.

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IMPORTANT

New fields/keys may be added at any point. You must be able to successfully process <<glossary:FAST>> messages that contain new fields/keys.

In the following sections, we describe the general structure and content of the ISO-8583 messages in the ISO8583: 1993 version.

FAST message nodes

<<glossary:FAST>> messages consist of the following nodes:

More details about the nodes:

The first node

The fundamental message types and descriptions are as follows:

• 0100 - Authorisation message
• 0120 - Advisement message
• 0400 - Reversal message
• 0420 - Reversal Advisement

The second node

The SUMMARY node holds the main financial data of the message.

Each SUMMARY object includes the following keys:

"SUMMARY": {  
   "TID": "",  
   "RID": "",  
   "PID": "",  
   "Client_Id": "",  
   "Transaction_Date_Time": "",  
   "Network": "",  
   "Spend_Type": "P",  
   "Spend_Location": "",  
   "Transaction_Amount": "",  
   "Transaction_Currency": "",  
   "Billing_Amount": "",  
   "Billing_Currency": "",  
   "Card_Use_Type": "",  
   "Customer_Validation": " ",  
   "Processor_Decision_Code": "",  
   "Processor_Reason_Code": "",  
   "Processor_Decision_Desc": "",  
   "Merchant_Category": "",  
   "Account_Id": "",  
   "Customer_Ac": "",  
   "Total_Fee_Bill": ""  
 },

The third node

The PROCESSOR_VALIDATIONS node holds data about the non-financial checks performed on the message.

Each PROCESSOR_VALIDATIONS object includes the following keys:

"PROCESSOR_VALIDATIONS": {
   "Pan_Check": "",
   "Pin_Check": "",
   "Expiry_Check": "",
   "Track_Check": "",
   "CVV_Type": "",
   "CVV_Check": "",
   "ARQC_Check": "",
   "3DS_Check": "",
   "Test_Matrix": "",
   "Test_Results": "",
   "Rules_Checked": "",
   "Rules_Triggered": "",
   "Rules_Decision": ""
 },

The fourth node

The fourth node of a FAST message, ISO_MSG, consists of the original ISO 8583 message received from the relevant scheme (Mastercard/Visa/Union Pay) or switch, in which the card PAN data has been tokenised (to Token ID) for security and <<glossary:PCI-DSS>> compliance

The fifth node

The Rules node provides all the rules listed under a RULES key as an array of the JSON object. Each rule object will reference the rule description and trigger(s) as well as the relevant rule action(s) that are triggered.

Additional controls may be applied at the authorisation level, based on transaction rules and limits that a bank requires, to monitor transactions against client-defined rules, i.e. fraud rules. These rules are set up in the Paymentology rules engine (PayRule) and the Credit engine, and one or more rules can be triggered for a single authorisation message, and each can have multiple actions based on client requirements.

The RULES node provides the structure outlining the rules applied and their respective results.
One or more rules can be triggered for a single authorisation message. Single rules can have multiple actions. All rules will be listed under key Rules as an array of JSON objects.

Under each rule object, there will be the following keys:

"RULES" : [ {
    "Rule_Id" : 1,
    "Rule_Type" : "Au",
    "Rule_Check_Result" : 0,
    "Pattern_Result" : false,
    "Current_Txn_Amt_Deviation" : -146100.0,
    "Aggregate_Deviation" : 0.0,
    "Count_Deviation" : 0
  ]}

Rules can have associated Actions, indicating:

• Act
• DE39
• Exit_Code
• Nwk_Status

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You can read more on Rules node data fields here.

The sixth node

The Decision Engine element contains only the data of triggered actions.

Each triggered action is represented via:

• id: The unique action ID stored in Paymentology's system
• typeName: The action type
• details: contains action specific data as well as the custom attributes
• attributes: Custom key-value data set by the client during action configuration.

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You can read more on Decision Engine node data fields here.

FAST message example

Below is an example of a <<glossary:FAST>> message.

{
  "MESSAGE_TYPE": {
    "Message_Type": "0100",
    "Message_Desc": "Authorisation Request"
  },
  "SUMMARY": {
    "TID": "2453301012345678996",
    "RID": "2412345",
    "PID": "1111",
    "Client_Id": "123456",
    "Transaction_Date_Time": "20-09-2023 08:21:41",
    "Network": "MC",
    "Spend_Type": "POS - Purchase",
    "Spend_Location": "W.H.Smith Signature    Edinburgh     GBR",
    "Transaction_Amount": "350",
    "Transaction_Currency": "HKD",
    "Billing_Amount": "350",
    "Billing_Currency": "HKD",
    "Card_Use_Type": "Chip",
    "Customer_Validation": "ARQC ",
    "Processor_Decision_Code": "00",
    "Processor_Reason_Code": "000",
    "Processor_Decision_Desc": "Approve",
    "Merchant_Category": "5499 - Miscellaneous Food Stores-Convenience Stores and Specialty Markets",
    "Account_Id": "298123456",
    "Customer_Ac": "NA",
    "Total_Fee_Bill": "0"
  },
  "PROCESSOR_VALIDATIONS": {
    "Pan_Check": "PASS",
    "Pin_Check": "NA",
    "Expiry_Check": "PASS",
    "Track_Check": "PASS",
    "CVV_Type": "4",
    "CVV_Check": "BYPASS",
    "ARQC_Check": "PASS",
    "3DS_Check": "NA",
    "Test_Matrix": "2447425042760349112",
    "Test_Results": "0",
    "Rules_Checked": "12345,12346,12347",
    "Rules_Triggered": "12347",
    "Rules_Decision": "00"
  },
  "ISO_MSG": {
    "DE2": "736346106",
    "DE3_1": "00",
    "DE3_2": "00",
    "DE3_3": "00",
    "DE4": "000000035000",
    "DE6": "000000035000",
    "DE7": "0920082141",
    "DE10": "61000000",
    "DE11": "000096",
    "DE12": "075120",
    "DE13": "0920",
    "DE14": "2407",
    "DE15": "0612",
    "DE16": "0612",
    "DE18": "5499",
    "DE22": "052",
    "DE23": "000",
    "DE32": "012345",
    "DE35": "736346106D2407***",
    "DE37": "085000100002",
    "DE38": "10577Z",
    "DE41": "12345678",
    "DE42": "123456789123456",
    "DE43": "W.H.Smith Signature    Edinburgh     GBR",
    "DE48": {
      "1": "R",
      "38": "Z"
    },
    "DE49": "344",
    "DE51": "344",
    "DE55": {
      "82": "5800",
      "95": "0000000000",
      "9F10": "010100A0030000C1",
      "9F27": "80",
      "9F36": "0028",
      "9F34": "1E0300",
      "9F33": "E0E8E8"
    },
    "DE61": "0000000000800826902101234",
    "DE63": "MCS0110QI",
    "DE95": "000000000000000000000000000000000000001000"
  },
  "RULES": [
    {
      "Rule_Id": 12345,
      "Rule_Type": "Au",
      "Rule_Check_Result": 0,
      "Pattern_Result": false,
      "Current_Txn_Amt_Deviation": 350,
      "Aggregate_Deviation": 0,
      "Count_Deviation": 0
    },
    {
      "Rule_Id": 12346,
      "Rule_Type": "Au",
      "Rule_Check_Result": 0,
      "Pattern_Result": false,
      "Current_Txn_Amt_Deviation": 0,
      "Aggregate_Deviation": 0,
      "Count_Deviation": 0,
    },
    {
      "Rule_Id": 12347,
      "Rule_Type": "Au",
      "Rule_Check_Result": 12,
      "Pattern_Result": true,
      "Current_Txn_Amt_Deviation": 30,
      "Aggregate_Deviation": 0,
      "Count_Deviation": 0,
    },
  ]
}

Clearing and settlement message payload

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Find out more on <<glossary:FAST>> clearing and settlement payload here.