ATM & POS Interface - T24

Functional Overview

1. ATM / POS Functionality

ATM Automated Teller Machine, widely used by consumers to perform financial transactions such as Cash Withdrawals, Cash Deposits, Cheque Book Request, Bill payments, Mobile Recharges, Funds Transfer between Accounts & non-financial transactions such as Account Balance Enquiry, Mini Statements Request , Account Statement Request, Cheque Book Requests etc.,

POS Point of Sale, this type of transaction is classified into two

1.    Card present  (Transactions performed over a physical machine)

2.    Card not present (Online Purchase)

All the mentioned transaction communicates directly to the core banking application (here it is T24). ISO8583 is the format which is opted by the financial institutions to read the financial / non-financial transaction messages that is sent via switches.

Note: The transaction types enabled in an ATM / POS machine differs from financial institutions based on their business necessity.

2. Functionality in T24

ATM interface is a middle layer that resides between Switch(ATM) and T24(Host), the middle layer is connected to the application server with a dedicate port, which listens for the incoming ISO messages from the interface. The incoming message is then converted to T24 readable format (OFS - Open Financial Service) to process the message. Either success / failure the response will be sent back to the switch in the same manner as it received. The ISO messages are transmitted from the Switch to T24 via TCP/IP.

Application Server can be configured for listening ISO messages on required number of ports (this is decided based on the usage volume of ATM/POS). Application servers supported by T24 ATM Interface.

 TC Server

 Jboss

 Websphere

 Weblogic 

3. How ATM / POS Works?

When a customer uses an ATM / POS terminal connected to the switch server, the switch sends a message to T24. Depending upon the message and various functions, accounting entries are generated in T24 and response message is sent either with an error or successful details back to the ATM Interface.

Once the interface is started, the parameters required for the Interface are read from the mapping tables. Java Listener listens to a port where ATM Switch will be sending the ISO8583 messages. Once the raw ISO8583 message is read from the port, ATM Interface converts this raw ISO message into OFS message format and sends it to T24, for the execution of corresponding transaction. After the transaction has been completed at T24, the response messages are formatted in ISO8583 format and sent back to ATM Switch.

The below picture is a generic demonstration of ATM functional flow in T24. 

The below picture is a generic flow chart for ISO message processing in T24

4. How to do ATM testing

          To test an ATM interfaces, it is must to know about ISO messages & their respective data elements in the message, Parameter setup in T24.

A. ISO Messages

          As mentioned ISO8583 is the format where the switch exchanges the communication of the transactions to the host (Core Banking System) made by a card. T24 supports ISO 8583:87 and ISO 8583:93 versions only, where all mentioned financial / non-financial transaction are supported by both the versions. ISO messages are made of three parts

Message type indicator (MTI)

The first 4 characters after header message is called MTI, indicates of what type of message either Online or Offline which defines how message should flow to the system.

Online – transaction that happens on real time which hits the host

Offline – transaction that hits the host after certain interval of time

Example:

0800 >> Request for network sign on

0810 >> Response for network sign on

0200 >> Online request for a financial transaction

0210 >> Online response for a financial transaction

0220 >> Offline request for a financial transaction

0221 >> Financial transactions repeat

0230 >> Offline response for a financial transaction

0420 >> Reversal request

0421 >> Reversal repeat

0430 >> Reversal response

• One or more bitmaps indicating data elements like Transaction Date / Amount / Base Currency / Account Currency / Card data / ATM ID / ATM Location / Country Code
• Reserved fields, Data elements indicating data elements Debit Account Number / Bank Institution ID / Credit Account No / Not used fields

Sample ISO Message:

ISO0160000700200B23CE4812EB08018000000001400000401200000000053071602121120480292951123470212201002126011826051020514745375576280500007084=20102211629092800000D13657222222000000  IO11129         INFICATT              TONTON          JB250                        634012NETWNETW-003013BNK NETW10100P116340800000009100131441350& 0000200350! BD00328 00000000000005307160000000000000000000634   TT T   T00000 00000000000000000000000000000000000000

The below table indicates the data elements & their values in each position

Position	Name	Type	Mandatory
1	Bit Map	b 64Bit	True
3	Processing code	n 6	True
4	Amount, transaction	n 12	True
7	Transmission date & time	n 10	True
11	Systems trace audit number	n 6	True
12	Time, local transaction (hhmmss)	n 6	True
13	Date, Local transaction (MMdd)	n 4	True
14	Date, Expiration	n 4	True
15	Date, Settlement	n 4	False
17	Date, capture	n 4	True
18	Merchant type	n 4	True
19	Acquiring institution country code	n 3	True
22	Point of service entry mode	n 3	True
25	Point of service condition code	n 2	True
27	Authorizing identification response length	n 1	False
32	Acquiring institution identification code	n ..11	True
35	Track 2 data	z ..37	True
37	Retrieval reference number	an 12	True
38	Authorization identification response	an 6	True
39	Response code	an 2	True
41	Card acceptor terminal identification	ans 16	True
42	Card acceptor identification code	ans 15	False
43	Card acceptor name/location	ans 40	True
44	Additional response data	an ..25	True
48	Additional data – private	an …999	False
49	Currency code, transaction	a 3	True
60	Reserved national	an …999	True
61	Reserved Private	ans …999	True
63	Reserved Private	ans …999	False
70	Network management Information code	n 3	False
90	Original data elements	n 42	False
95	Replacement amounts	n 42	False
100	Receiving institution identification code	n ..11	True
102	Account identification 1	ans ..28	True
103	Account identification 2	ans ..28	False
121	Reserved for private use	ans …999	False
123	Reserved for private use	ans …999	False
125	Reserved for private use	ans …999	False
126	Reserved for private use	ans …999	True

ATM Parameterization

The following are the files that are configured in T24 to process the ISO messages              

ATM.PARAMETER >> The file stores the details about user name for the ATM to access T24 application, Bank Institution ID, ISO version, Processing Code, Mapping filed for unique ID of transaction, Network ID (VISA/Master), Default ATM  / POS branch & ATM / POS bin numbers. 

ATM.BRANCH >> This file store the details about the ATM machines belonging to which branch / location, type of machine (CDM only / ATM & CDM / ATM only), corresponding ATM GL account numbers.

ATM.BIN.ACCT >> This file stores the details about receivable and payable accounts for visa/master card transactions done via ATM only. Id of each record is formed based on the Acquirer bin of other banks or first 6 digits of PAN No or Network numbers.

ATM.POS.BIN.ACCT >> This file is similar to ATM.BIN.ACCT where details about the receivable and payable accounts for visa/master card transactions done via POS only. Id of each record is formed based on the Acquirer bin of other banks or first 6 digits of PAN No or Network numbers.

ATM.CHG.TABLE >> This file stores charges for all transactions.

ATM.CHG.DETAIL >> This files gets updated once the details / setup is verified in ATM.CHG.TABLE

ATM.SPLIT.CHG.TABLE >> This files stores the values whether the multiple entries to be raised for the transaction (charges separately). This records defined here should be internally used in ATM.CHG.TABLE

ATM.RES.CODE.TABLE >> This file stores the details about what sort of response to be sent to the switch for the processed transactions.

Example:

Message.1: Invalid Account Response Code.1: 76, means the host will respond with “76”, as response code for the failure transactions due to invalid accounts.

INTRF.MAPPING >> this files stores the details about the values that to be consider for processing the transaction. Mapping records for each transaction, which indicates what application, version to be used to raise accounting entries.

5. Challenges faced

• Connection establishment between the SWITCH and application server
• T24 fails to read the messages from the application server queue, configuration changes to recognize the incoming messages (Ex: Messages available in MQ, but T24 fails to process it)
• Transaction processing fails due connection timeout between the SWITCH & application server (Timeout settings that need to be handled at SWITCH, application server & the host T24)
• Parameter Setup missing in T24
• Transaction processing per minute, if throughput of transaction is more in number, TOT of each transactions increases (performance measures)

6. Mitigate Challenges

•  Monitoring the listener port & the sender port configurations frequently
• Monitoring the queue depth frequently & clearing the messages from the queue if by taking backup of the data in the queue
• Revisit the above mentioned parameter setup related to ATM in T24
• Get the details from the bank about their ATM usage transactions per day & accordingly configuration changes needs to be setup at application server level (performance testing)
• Add ATM matrix for better coverage
• Sample test cases that to be covered

7. Frequently faced defects

• Consideration of locked (blocked) amounts in the account
• Example:
•  Wrong balance is shown to the customers when balance enquiry transaction is performed
•  Raising wrong account entries in case of insufficient balances

• Consideration of other branch customer accounts and type of account for financial transactions
• Example:
• Customer accounts are differentiated based on which branch they belong, so frequent failure happens due to other branch accounts (apart from Main Brach)
• Financial transaction failing for Savings account but working for current account

• Incorrect mapping of response code which is sent back to the SWITCH
• Example:
• Consider that the SWITCH expects “00” response code for any successful transaction, but instead some other code is sent, in this case the SWITCH considers the transaction as failure but the customer account would have been debited

•  Off us transaction failures
• Example:
• Cash withdrawal from other financial institutions that does not use T24 ATM interfaces
• Cash withdrawal using other financial institutions card / credit card in SWITCH that is integrated with T24 ATM Interface

•  View Mini statement
• Example:
• Failure happens due to length of the transaction description of an account
• When no transactions are available in an account

•  Transactional charges / fees not debited from the account
• Example:
• Transaction fee which supposed to be collected for the financial transaction is not debited from the customer account, due to incorrect charge setup and also the logic of handling debit entries for fee transactional charges   

•  Void financial transactions
• Example:
• Transactions that supposed to be reversed are not exactly reversed in the account, this mostly happens in case of transaction time out.

Note: 
Without a physical ATM / Simulator, T24 ATM Interface can be tested by placing the incoming ISO message in the application server or post the ISO message via telnet.

Performance of the T24 ATM interface can be tested by sending ISO messages as a bunch to the application server queue.