Modules/Functionalities

A description of the functionality of each module is explained below:

1. Communications Driver (tcpip)

Communication driver manage message ports and communication protocols. It is logically connected to a network formatter or device server. Each driver uses a specific protocol to receive messages from an external device or network. It passes the messages to the formatter with the header and control information stripped from the body of the message. It is used to ensure error free of message to be sent and received by the IST/Switch system. It is also control the flow of message into the IST/Switch system in case congestion within the system.

The communication driver proposed are multi-threaded applications that provide high performance, easy to configure, reusable communication driver supporting a wide variety of platforms. The multi-thread architecture enables enhanced performance in both uniprocessor and multiprocessor environments. It also allows separating logical  (program) concurrency from the required real concurrency, and controlling both within a single programming model.



2. POS modules (hypercom)

The POS modules are used to translate transactions from the devices to IST. Messages received in the external message format (XMF), i.e. format adopted by the devices such as Hypercom, Verifone and Ingenico, are converted to the Internal Message Format (IMF) to be processed by IST. The modules will also convert outgoing messages to these devices from IMF to XMF. Additional terminal functionality is also performed at this level. The types of POS terminals supported are Hypercom, Verifone and Ingenico. The POS modules in IST are capable of supporting Visa 1st Generation, Visa 2nd Generation, Hypercom variation of ISO8583 and Verifone variation of ISO8583 message formats.



3. Formatter (Bank formatter)

Formatter is used to translate incoming messages (i.e. format adopted by the external interface such as Bank interface) into a standard internal format for IST/Switch kernel (Shared Cash) to process. Shared Cash (SHC) sends outward bound messages to the formatter for translation into a standard external format, such as ISO 8583, used by networks and participating financial institutions. This enables financial institutions to use their own proprietary systems and still exchange data via IST/Switch.



4. External card association formatters (Visa and MasterCard)

Formatters used to translate incoming messages from Visa and MasterCard into a standard internal format for IST/Switch kernel (Shared Cash). Shared Cash (SHC) sends outward bound messages to the formatter for translation into a standard external format, such as ISO 8583, used by networks and participating financial institutions.



5. Shared Cash (SHC)

The SHC subsystem is the message switching and processing core for financial transactions in the IST/Switch. It manages the authentication, authorization, routing, and logging of transaction messages received by IST/Switch, and generates responses to the issuing agencies. SHC can co-ordinate message sequences for a transaction, acting as an intermediary for financial institutions in situations where a customer initiates a transaction on the ATM of one institution with the card of another.

SHC can act as an authorization agent, authorizing or denying transaction requests from a customer, such as a cardholder, or it can act as a router, simply passing transaction requests to the appropriate host or network for processing by the financial institution. When SHC acts as an agent, information about customers is generally supplied to it by the customers’ financial institution.

SHC processes messages which fall into three main categories: system messages, administrative messages, and financial transactions. It determines which category a message belongs to by examining the message header information.

SHC manages outbound and inbound messages (transactions) throughout their lifecycle:

• it times transactions using the event manager;
• it routes transaction and other messages based on their requirements;
• it logs transaction messages in the transaction log database;
• it handles network management messages originating from the network manager subsystem;
• it exchanges encryption keys between networks to maintain the privacy of all transaction  
messages transmitted to and from the IST/Switch;
• it monitors network connections to ensure the integrity of the network and its connections.

Callback mechanism is introduced into SHC to make the switch more powerful and flexible, and provide more control to an application developer. Application programmers may use the callback functions to extend the application business logic of IST/Switch in addition to the services that is currently provided. Following are notable entry points provided:
• Before/After editing: allow programmers to further enrich the message.
• Before routing (switching out/responding back): timers can be adjusted on a BIN/Acquirer  
basis, issuing end-point decisions like transaction fees etc.
• Before logging: allow special fields to be logged into IST transaction log table.



6. IST Authorization (pre-auth)

The IST authorization server is used to verify and validate a transaction before it is routed to a host. This module will reject transactions that have failed the verification process. It is also used to authorize certain transactions that are not processed by the host such as PIN change. In the event that stand-in is required, this module is also able to verify and validate a transaction during situations of offline processing. Approved transactions will be stored in SAF and forwarded to the issuer or host application once the link to the appropriate system is re-established. IST/Switch supports 2 different modes of stand-in: negative file and positive file. Negative file stand-in can be used if the card and account details are not available. Stand-in will be performed based on configured limits. Positive file stand-in can be used if the card and account details are available. The balances have to be updated to allow the authorization module in IST to authorize the transactions.

IST authorization server is fully customizable module according to the need of customer. For example, it can be enhanced to support validation of floor limit and merchant floor limit before incoming transaction messages are forwarded to backend host for authorization.



7. Security Subsystem

Hardware Security Module (HSM) is an independent and secure device that is impenetrable to wire-tapping, program modification, and physical machine break-ins. It provides cryptographic functions that support network and point-to-point data security. An HSM provides safe environment for installing and generating security keys. This device can generate, verify, translate, and encrypt keys.

In most implementations of IST/Switch system, a HSM is used to implement the DES or Triple DES (3DES) algorithms. The HSM implements DES or 3DES in hardware to provide the maximum level of security (cryptographic security). IST security subsystem support interface to HSM hardware from Racal, Atalla and Excrypt.

Services that are performed by the security subsystem include pin translation and verification, MAC generation and verification, and CVV verification. The pin encryption methods supported in IST are Visa PVV and the IBM Pin Offset method. IST/Switch is capable of supporting the single DES as well as the Triple DES (3DES) method of pin block encryption method.



8. Store-and-Forward Subsystem (SAF)

IST/Switch has “store and forward” capabilities. Transactions that are required to be “store and forward” such as reversals and transactions authorized during stand-in are stored in a SAF file.  The SAF replay is provided by the istreplay task which replays transactions stored in an institution’s Store and Forward (SAF) file. The SAF file contains transactions (01xx, 02xx, 04xx, 05xx and internal 0270) authorized by SHC and written to the institution’s SAF file during SAF processing. These transactions remain in the SAF file until Istreplay is invoked and the messages are sent to the institution host for force-posting.

The Istreplay task reads and processes transactions from an institution’s SAF file by transforming them from request messages to advice messages and sending them to SHC. SHC processes each advice message in accordance with the BIN profile of the institution. Istreplay awaits a response from each advice message from SHC before proceeding to read and process the next transaction in the SAF file.



9. TSF

TSF module is the utility to refresh/update IST tables via supported refresh file formats. It reads and processes merchant and terminal refresh files provided by the Bank Host.



10. IST/Monitor

IST/Monitor is a powerful and comprehensive application that allows an operator to monitor the entire IST/Switch network from one node. The new interface facilitates configuration of the IST/Switch monitor and addresses the following topics:



• Communication Status
– Displays and controls all message ports created by applications
– Supports the following functions on message ports:
i) Start a port that is marked “stopped”.
ii) Stop access to a port.
iii) Toggle trace option for the selected message port.



• ATM Device Status
– Displays and controls access to ATM devices
– Supports the following functions on ATM device:
i) Put one or more devices into service
ii) Take one or more devices out of service
iii) Show a device status
iv) Load ATM FIT (financial institution tables) to a device
v) Load ATM states (most models) to a device
vi) Load ATM screens (most models) to a device
vii) Load miscellaneous information to the device
viii) Initialize the device (states, fits, configuration and screens) in one step
ix) Change encryption keys with a device
x) Clear the IST/Switch servers' idea of the fitness of each sub-device for an ATM device
xi) Clear the reported status codes for a device



• Institution Status
– Displays and controls all institutions in IST/Switch system
– Supports the following functions:
i) Set an institution up or down
ii) Start replay institution
iii) Start MAC and PIN key exchange



• Task Status
– Displays and manages tasks which are part of an IST/Switch application. A task is considered part of an IST/Switch application if it was initiated by the task manager, either during start-up, through the TASK configuration group, or during the normal course of processing.
– Supports the following functions:
i) Start a new task
ii) Stop a currently executing task
iii) Filter messages



• Event Status
– Displays all pending system events. Events are continuously being created and destroyed  during the life of the system. They serve mainly to aid applications in timing out pending   transactions. For example, the SHC application uses one event for each message it intends to track.



• Message/Error Distribution Statistics
– Displays the distribution of transaction types and error codes generated. The figures accumulated are on-line numbers and represent the most current figures available. These statistics are compiled by the SHC as it processes each inbound and outbound transaction. These statistics are refreshed every day by the switch.



• Mailbox Status
– Displays and manages IST/Switch mailbox system
– Supports the following functions:
i) Create a mailbox
ii) Delete a mailbox
iii) Clear the message queue for a particular mailbox



• System Messages
– Provides a view into the real-time system messages at the IST/Switch system

• General Information
– Supports the following functions:
i) Provides an indicator of disk space available (to reduce crashes resulting from low disk space)
ii) Indicates the current host
iii) Show the current IST/Switch system event and message queues in used



11. IST/Switch Database

IST/Switch Database subsystem provides an access mechanism for reading and updating the database without the need for in-depth knowledge of the type of database in use.

It is flexible enough to interface with a number of relational database management systems such as Oracle, Informix, Sybase, and DB2. It maintains compatibility across systems and insulates the calling program from change if the underlying database platform is replaced.

The IST database interface has evolved from an implementation based on indexed files to the present one, based on various relational database systems. Most of the API set has retained the orientation towards file and record-based operations. Over time, additional API calls have been added to support some of the features specific to relational database interfaces creating the DBM Layer. Subsequently, the Low Level IST Database Layer has been created to provide more flexibility in using features of relational database systems.

The current IST database interface integrates two layers:
• DBM Layer, and
• Low Level IST Database Layer

The DBM Layer remains as a set of interchangeable shared libraries, each implementing the standard DBM API for a particular DBMS. The Low Level IST Database Layer exists between the application code and the “native” client library code. The IST database interface enables you to:
• Access rows of a single table or multiple joined tables either using a notion of predefinedindexes (sets of key columns) or with an explicit WHERE clause. You can access the rows sequentially or randomly, for an update or in read-only mode
• Update either the entire record or its application-specified columns
• Support large binary and text data columns (potentially more than one in a single row)
• Provide support for decimal numbers of varying precision and scale
• Prepare and repeatedly execute database requests such as: SELECT, INSERT, UPDATE, or DELETE. You can execute a database transaction by committing it or rolling it back.