Patent Publication Number: US-2011078083-A1

Title: Electronic draft capture

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     The present application is a continuation of and claims priority of U.S. patent application Ser. No. 10/620,293, filed Jul. 15, 2003, the content of which is hereby incorporated by reference in its entirety. 
    
    
     BACKGROUND OF THE INVENTION 
     The present invention relates to processing financial transaction authorization requests from merchants. More specifically, the present invention relates to a payment processing gateway for use in processing financial transaction authorization requests and a protocol accessing such a gateway. 
     In a retail transaction, a purchaser purchases a retail product from a merchant. Retail transactions have been used throughout much of human history. Having evolved from a simple barter system, there has been an ongoing trend to make such transactions more efficient and convenient for the consumer and the merchant. As an alternative to barter, money was used to represent the value of items to allow more flexibility in such transactions. Next, there was the realization that the money involved in the transaction did not need to be physically present at the transaction time. For example, a debit ledger can be maintained by the merchant and used to record sales in which credit was extended to the consumer. This allowed the consumer to pay for the goods at a future date. Checking systems are also employed in which a check is issued allowing the recipient to draw on those funds from a bank. 
     Charge, debit cards, electronic checks and the like (“financial cards”) provide far more convenience to the consumer than the use of physical checks. Originally, copies of receipts from such financial card transactions were simply maintained by the merchant and periodically processed. Eventually real time authorization techniques were provided by financial card issuers. In such systems, a merchant is able to obtain an authorization from the financial card issuer prior to completion of the retail transaction. Various types of authorization can be used, for example an authorization can be obtained through oral communication, such as through a telephone call. Authorizations can also be obtained through digital communication techniques. 
     Presently, many retail locations employ point of sale (POS) devices in which a magnetic strip on a financial card is “swiped” through a card reader. Data on a “smartcard” chip can also be read. The data can be read using a magnetic sensor, electrical contacts, a radio frequency (RF) connection, or through other techniques. The card reader or a device connected to the reader, initiates a telephone call with an authorization center. The authorization center is able to immediately authorize or decline a particular transaction. The point of sale device informs personnel at the retail location of the result of the authorization request. If the transaction is questionable, the merchant can be required to obtain further information for verifying the card holding prior to providing authorization for the transaction. With the advent of the Internet, such authorization procedures are moving away from point to point telephone connections and are beginning to exploit the connectivity that the Internet provides. In such transactions, a device at the point of sale uses a secure communication technique, such as a Secure Socket Layer (SSL), to communicate with a authorization gateway. The gateway is capable of simultaneously communicating with point of sale devices from multiple merchants. The gateway contacts the appropriate financial institution regarding the authorization request and relays the result of the authorization request back to the appropriate point of sale device through the Internet connection. There is an ongoing need to improve the performance and convenience of such transactions. 
     SUMMARY OF THE INVENTION 
     Embodiments of systems and methods for processing financial transactions are disclosed herein. In one embodiment, an authorization request is transmitted to a payment processing gateway server. The authorization request includes a supplemental header having a contract identification field that stores an identification of a contract between a merchant and a payment provider. A transaction response transmission is received from the payment processing gateway server in response to the authorization request. The transaction response transmission includes a transaction response header and a response data component. The transaction response header includes identification of a particular transaction to which the transaction response transmission is applicable. The response data component includes an indication that the contract is invalid. The indication that the contract is invalid is responded to by facilitating a rejection of the financial transaction. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a simplified diagram showing a payment processing gateway coupling a point of sale device to financial institutions across public and financial networks. 
         FIG. 2  is a block diagram showing the point of sale device of  FIG. 1  in greater detail. 
         FIG. 3  is a block diagram showing the payment processing gateway of  FIG. 1  in greater detail. 
         FIG. 4  is a block diagram of a general computing environment in which embodiments of the present invention may be practiced. 
         FIG. 5  is a block diagram showing an authorization request data packet. 
         FIG. 6  is a block diagram showing an authorization response data packet. 
     
    
    
     DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS 
     The present invention provides a protocol and implementation to support various forms of electronic fund transaction types. Examples of electronic fund transactions are those which are based upon credit cards, charge cards, debit cards, check verification, gift cards, coupons, etc. As used herein, these various types of electronic fund transactions are referred to as “financial transactions” or “financial cards,” although a physical card is not required. Various transaction types are supported including the types “authorize”, “void”, “return”, “settle”, etc. 
     Point of sale (POS) terminals communicate directly over a public network such as the Internet, or through a retail server system which couples to the public network, to a payment processing gateway server. The payment processing gateway server provides a link between authorization requests received from the public network and at least one financial network. The financial network provides communications with at least one financial institution which is capable of authorizing the particular transaction. The financial network can be a private network or can be a secure link over a public network. 
       FIG. 1  is a simplified block diagram of an electronic fund transaction processing system  10  in accordance with one example embodiment of the present invention. The transaction processing system  10  includes a point of sale (POS) device  12  which couples to a public network  14 , such as the Internet. A payment processing gateway  16  couples to the public network  14  and is in communication with the point of sale device  12 . The payment processing gateway  16  couples to at least one financial network  18 A,  18 B . . .  18 N. The financial network  18 A-N can be a private network or a secure communication link over a public network such as the Internet. At least one financial institution  20 A,  20 B . . .  20 N couples to each of the respective financial networks  18 A,  18 B . . .  18 N. Any number of financial institutions  20 A-N can couple to a single financial network  18 A-N. 
     The point of sale device  12  can be physically located at a retail location such as a retail store. The device  12  can comprise an individual cash register, for example, or can be a retail server system which is used to connect to multiple point of sale devices. Such a retail server system can provide additional functionality such as inventory control, theft prevention, etc. The retail server system can be implemented in a separate server or in a peer-to-peer architecture. The retail location can include a local area network which couples to the point of sale device  12 . In some systems, wireless networks are provided. In one aspect, the present invention reduces communication overhead on such networks. 
       FIG. 2  is a simplified block diagram of point of the sale device  12  shown in  FIG. 1  and which includes a user input/output  30 . The user input/output  30  can comprise, for example, a display, keyboard, a touch screen, pointing device, card reader such as a magnetic card reader, RFID reader, magnetic stripe reader, smartcard reader, voice recognition device or the like, weighing scale, or any of the various inputs and outputs discussed below or known in the art. The input/output  30  couples to a processor system  32  which includes a memory  34 . Memory  34  is used for storing programming instructions as well as data. A network interface  36  is used to couple the processor system  32  to the public network  14  over a physical layer  38 . User input/output  30  is used to initiate a financial card authorization request by processor  32 . Processor  32  formats the request in accordance with the appropriate protocol format for transmission by network interface  36  over the physical layer  38 . The physical layer  38  can be any type of network connection. In addition, processor system  32  can perform other functions such as maintain inventory, perform cash register operations, provide instructions to an operator, provide information or advertisements to a consumer, etc. 
       FIG. 3  is a simplified block diagram of payment processing gateway  16 . Gateway  16  includes a network interface  40  configured to couple to the public network  14  through physical layer  42 . A processor system  44  includes a memory  47  which contains programming instructions and data. Processor system  44  couples to public network  14  through interface  40  and to financial networks  18 A-N through a network interface  46 . Network interface  46  couples to financial network  18 A-N through physical layer  48 . 
     In operation, gateway  16  receives authorization requests from point of sale device  12  over public network  14 . The authorization requests are formatted in accordance with the appropriate transmission protocol for transmission over financial network  18 A-N to a respective financial institution  20 A-N. When gateway  16  receives a response to an authorization request from the appropriate financial institution  20 A- 20 N, the result is relayed back to the respective point of sale device  12  through the public network  14 . In accordance with one transmission protocol, the response transmission is identified such that the point of sale device  12  is able to determine to which authorization request the response message relates. However, such a transaction identification is not required when a single authorization request is sent over a synchronous connection, such as a single credit card transaction. In this case, the point of sale device  12  can wait for a return value to an httpost, or wait on a dedication socket, as there are no other transactions which must be followed. However, if multiple transaction authorization requests are sent, either at the point of sale device or through a retail server system, or if multiple transactions are bundled into a single message, or for some other reason a synchronous responses are supported, such a transaction identification can be used. 
     As illustrated below in greater detail, processor system  44  can have other inputs, outputs or configurations. The network interface  46  and physical layer  48  can be in accordance with any appropriate standard or protocol. 
       FIG. 4  illustrates an example of a suitable computing system environment  100  on which the invention may be implemented. System environment  100  can implement point of sale device  12  and/or payment processing gateway  16 . The devices, for example payment processing gateway  16 , can be implemented across multiple environments  100 . The computing system environment  100  is only one example of a suitable computing environment and is not intended to suggest any limitation as to the scope of use or functionality of the invention. Neither should the computing environment  100  be interpreted as having any dependency or requirement relating to any one or combination of components illustrated in the exemplary operating environment  100 . 
     The invention can be implemented in numerous other general purpose or special purpose computing system environments or configurations. Examples of well-known computing systems, environments, and/or configurations that may be suitable for use with the invention include, but are not limited to, personal computers, server computers, hand-held or laptop devices, multiprocessor systems, microprocessor-based systems, programmable consumer electronics, network PCs, minicomputers, mainframe computers, telephony systems, dedicated custom hardware, distributed computing environments that include any of the above systems or devices, and the like. 
     The invention may be described in the general context of computer-executable instructions, such as program modules, being executed by a computer. Generally, program modules include routines, programs, objects, components, data structures, etc. that perform particular tasks or implement particular abstract data types. In some embodiments, the invention is designed to be practiced in distributed computing environments where tasks are performed by remote processing devices that are linked through a communications network. In a distributed computing environment, program modules are located in both local and remote computer storage media including memory storage devices. 
     With reference to  FIG. 4 , an exemplary system for implementing the invention includes a one or more general-purpose computing devices in the form of a computer  110 . Components of computer  110  may include, but are not limited to, a processing unit  120 , a system memory  130 , and a system bus  121  that couples various system components including the system memory to the processing unit  120 . The system bus  121  may be any of several types of bus structures including a memory bus or memory controller, a peripheral bus, and a local bus using any of a variety of bus architectures. By way of example, and not limitation, such architectures include Industry Standard Architecture (ISA) bus, Micro Channel Architecture (MCA) bus, Enhanced ISA (EISA) bus, Video Electronics Standards Association (VESA) local bus, and Peripheral Component Interconnect (PCI) bus also known as Mezzanine bus. 
     Computer  110  typically includes a variety of computer readable media. Computer readable media can be any available media that can be accessed by computer  110  and includes both volatile and nonvolatile media, removable and non-removable media. By way of example, and not limitation, computer readable media may comprise computer storage media and communication media. Computer storage media includes both volatile and nonvolatile, removable and non-removable media implemented in any method or technology for storage of information such as computer readable instructions, data structures, program modules or other data. Computer storage media includes, but is not limited to, RAM, ROM, EEPROM, flash memory or other memory technology, CD-ROM, digital versatile disks (DVD) or other optical disk storage, magnetic cassettes, magnetic tape, magnetic disk storage or other magnetic storage devices, or any other medium which can be used to store the desired information and which can be accessed by computer  110 . Communication media typically embodies computer readable instructions, data structures, program modules or other data in a modulated data signal such as a carrier wave or other transport mechanism and includes any information delivery media. The term “modulated data signal” means a signal that has one or more of its characteristics set or changed in such a manner as to encode information in the signal. By way of example, and not limitation, communication media includes wired media such as a wired network or direct-wired connection, and wireless media such as acoustic, RF, infrared and other wireless media. Combinations of any of the above should also be included within the scope of computer readable media. 
     The system memory  130  includes computer storage media in the form of volatile and/or nonvolatile memory such as read only memory (ROM)  131  and random access memory (RAM)  132 . A basic input/output system  133  (BIOS), containing the basic routines that help to transfer information between elements within computer  110 , such as during start-up, is typically stored in ROM  131 . RAM  132  typically contains data and/or program modules that are immediately accessible to and/or presently being operated on by processing unit  120 . By way of example, and not limitation,  FIG. 3  illustrates operating system  134 , application programs  135 , other program modules  136 , and program data  137 . 
     The computer  110  may also include other removable/non-removable volatile/nonvolatile computer storage media. By way of example only,  FIG. 4  illustrates a hard disk drive  141  that reads from or writes to non-removable, nonvolatile magnetic media, a magnetic disk drive  151  that reads from or writes to a removable, nonvolatile magnetic disk  152 , and an optical disk drive  155  that reads from or writes to a removable, nonvolatile optical disk  156  such as a CD ROM or other optical media. Other removable/non-removable, volatile/nonvolatile computer storage media that can be used in the exemplary operating environment include, but are not limited to, magnetic tape cassettes, flash memory cards, digital versatile disks, digital video tape, solid state RAM, solid state ROM, and the like. The hard disk drive  141  is typically connected to the system bus  121  through a non-removable memory interface such as interface  140 , and magnetic disk drive  151  and optical disk drive  155  are typically connected to the system bus  121  by a removable memory interface, such as interface  150 . 
     The drives and their associated computer storage media discussed above and illustrated in  FIG. 4 , provide storage of computer readable instructions, data structures, program modules and other data for the computer  110 . In  FIG. 4 , for example, hard disk drive  141  is illustrated as storing operating system  144 , application programs  145 , other program modules  146 , and program data  147 . Note that these components can either be the same as or different from operating system  134 , application programs  135 , other program modules  136 , and program data  137 . Operating system  144 , application programs  145 , other program modules  146 , and program data  147  are given different numbers here to illustrate that, at a minimum, they are different copies. 
     A user may enter commands and information into the computer  110  through input devices such as a keyboard  162 , a microphone  163 , and a pointing device  161 , such as a mouse, trackball or touch pad. Other input devices (not shown) may include a joystick, game pad, satellite dish, scanner, or the like. These and other input devices are often connected to the processing unit  120  through a user input interface  160  that is coupled to a system bus, but may be connected by other interface and bus structures, such as a parallel port, game port or a universal serial bus (USB). The system bus may be implemented using any appropriate techniques. A monitor  191  or other type of display device is also connected to the system bus  121  via an interface, such as a video interface  190 . In addition to the monitor, computers may also include other peripheral output devices such as speakers  197 , printer  196 , pole displays, modems, network interface cards, etc. which may be connected through an output peripheral interface  195 . 
     The computer  110  is operated in a networked environment using logical connections to one or more remote computers, such as a remote computer  180 . The remote computer  180  may be a personal computer, a hand-held device, a server, a router, a network PC, a peer device or other common network node, and typically includes many or all of the elements described above relative to the computer  110 . The logical connections depicted in  FIG. 4  include a local area network (LAN)  171  and a wide area network (WAN)  173 , but may also include other networks. Such networking environments are commonplace in offices, enterprise-wide computer networks, intranets and the Internet. 
     When used in a LAN networking environment, the computer  110  is connected to the LAN  171  through a network interface or adapter  170 . The WAN networking environment is provided by the public network  14  or private networks  18 A-N. The computer  110  typically includes a modem  172  network interface card, or other means for establishing communications over the WAN  173 , such as the Internet. A network connection to the WAN may also be through a gateway, router, proxy, or other connection to the WAN over the LAN. The modem  172 , which may be internal or external, may be connected to the system bus  121  via the user input interface  160 , or other appropriate mechanism. In a networked environment, program modules depicted relative to the computer  110 , or portions thereof, may be stored in the remote memory storage device. By way of example, and not limitation,  FIG. 4  illustrates remote application programs  185  as residing on remote computer  180 . It will be appreciated that the network connections shown are exemplary and other means of establishing a communications link between the computers may be used. 
     In one aspect, the present invention provides a new protocol for transmission of authorization requests and/or authorization responses between point of sale device  12  and payment processing gateway  16  over public network  14 . The protocol can be configured for optimized implementation with retail management software which operates on a retail server system running on the gateway  16 . In some embodiments, data can be preconfigured or otherwise previously stored in a database in memory  47  on the payment processing gateway  16  such that the data does not need to be retransmitted over the public network  14 . This provides increased security while reducing transmission overhead. 
     In one aspect, a supplemental header is pre-pended to the authorization request “payload”.  FIG. 5  is a block diagram showing an example authorization request  200 . Authorization request  200  includes a transaction specific data field  202 , cache-key field  204  and a cacheable data field  206 . The supplemental header field  208  is shown pre-pended to the authorization request  200  on top of the cacheable data  206 . The supplemental header carries a small amount of data which is used as a key to index a database in payment processing gateway  16 . One example of such a field is one which identifies the financial contract(s) and terms of operation for a particular acquiring banks or financial networks and the payment gateway provider. Such a “contract ID” field can be used by the payment processing gateway  16  to access a small list of valid contract IDs. This accessing can be through a simple in-memory list or an in-memory hash table to improve performance. If a particular transaction request arrives at the payment processing gateway  16  with an invalid contract ID, the payment processing gateway  16  can reject the authorization request because a valid contract is not properly identified for the particular merchant who sent the authorization request  200 . In another example, the contract ID can be used to reference a particular subset of a group of valid financial networks, for example, an issuing financial institution frequently used more than one financial network and an acquiring bank or financial institution will indicate which subset of the various networks can be used by the merchant. 
     The rejection from the payment processing gateway  16  can be in the form of an authorization or transaction response transmission  230  shown in  FIG. 6 . A transaction response can include a transaction identification header field  232  and a response data field  234 . The transaction identification field  232  identifies a particular transaction to which the response  230  is applicable. For example, a merchant may issue multiple transaction authorization requests  200  within a short period of time and the transaction identification field  232  is used to match a particular response with the appropriate request. As discussed above, the transaction ID is not required in all embodiments. The response field  234  includes data which indicates the response to the authorization request  200  such as “authorized”, “declined”, “hold card”, “cut card”, “bad card”, “call issuer for further information”, or request additional information from the purchaser, for example, to verify the authenticity of the card holder. As discussed below, the gateway  16  can also request transmission of cacheable data to populate a cache. If the contract ID for the supplemental header  208  is invalid, the payment processing gateway  16  can provide a response  234  to the authorization request  200  which indicates that the contract is invalid. 
     The contract ID field can also be used to audit transactions by payment processing gateway  16 . This auditing can be used to ensure that merchants utilizing the payment processing gateway  16 , or the financial institutions utilizing payment processing gateway  16 , are properly charged for the use of the service. Further, the contact ID field can be used to analyze transactions to determine the source of the transactions, destination of the transaction, particular merchants involved, particular terms of the contract, etc. In one specific example, the contract identification comprises two bytes of 8 bits each. 
     In another example, the supplemental header  208  includes a payment type field. The payment type field is used to provide information to the payment processing gateway  16  as to which particular financial network  18 A-N should be used for authorizing the transaction. For example, a particular financial network  18 A-N may be for credit transactions of a particular type of debit card, while another financial network  18 A-N may be for use with credit cards. Other financial networks may be directed to advance payment types such as gift cards, coupons, smart credit cards, “microcredits”, etc. “Microcredits” are directed to a credit format in which small dollar amount transactions may be performed through credit in a cost effective manner. The payment type field can also indicate the particular protocol used by the back-end financial network  18 A-N and often within payload of the transmission, i.e., the transaction specific data  202 . 
     The transaction authorization protocol  200  illustrated in  FIG. 5  also provides a cache-key field  204 . The cache-key  204  can be used to uniquely identify a particular shop or store submitting an authorization request. Merchant data can also be cached, for example for merchants with multiple stores. The payment processing gateway  16  can retrieve cache data within memory  34  illustrated in  FIG. 2  based upon the cache-key. The cache data can be merchant or store invariant data information described below in more detail. In one specific embodiment, the cache-key field  204  comprises a 128 bit data field. The data field can be used to carry a GUID (Globally Unique Identifier). In another specific example, 12 bytes of the 128 bits identifies a particular merchant while the remaining 4 bytes identifies a particular store of that merchant. 
     The authorization request  200  may also contain cache-able data  206 . Typical prior art financial transaction protocols are capable of carrying a fairly rich set of merchant data, including for example, merchant name (25 bytes), country (3 bytes), state (2 bytes), location (13 bytes), city code/zip code (3 bytes), merchant category (4 bytes), acquirer bin (6 bytes), time zone differential (3 bytes), merchant category code (4 bytes), extra field separators for ease of viewing (4 bytes) and others. The total can be more than 66 bytes of data for the main authorization message in a T-format authorization request message (direct debit). Typically, all of this data must be transmitted with each authorization request. 
     With the present invention, the transaction invariant data can be cached in memory  34  of payment gateway  16 . In typical prior art gateways, such a cache would provide limited benefits due to server performance limitations and the difficulty of maintaining state across multiple servers arranged in a cluster. For example, the state of a particular transaction would be required to be maintained across a cluster of servers in a performat manner because there is a relatively high volume of authorization request which must be processed in near real time. Further, it is difficult to ensure that cached data is maintained or otherwise restored when a server is reset. 
     Web servers, for example, tend to be inherently stateless. With the present invention, payment processing gateway  16  is configured as a web server offering a web service which maintains state using a cache as desired in order to support such caching operations. The cache can be through any appropriate caching technique such as a shared file, a database, etc. Preferably, a caching mechanism is utilized which provides high performance and operates very efficiently to support large numbers of simultaneous transactions. In one aspect, the merchant invariant data is cached in volatile memory (i.e., RAM) of the payment processing gateway  16 . For example, by caching 100 bytes of data per merchant and with 200,000 merchants, 20 megabytes of memory world be utilized. 
     Although this caching operation is particularly useful for authorization requests, the caching can also be utilized with settlement requests. A settlement request typically occurs less frequently than an authorization request. In a settlement request, a number of transactions are typically “batched” together for settlement with the appropriate financial institution. The settlement process involves the transfer of funds from the appropriate financial institution to the account of the merchant. 
     If the payment processing gateway  16  is implemented in a number of different servers, such as that provided by a web cluster, the caching of merchant or transaction invariant data can be achieved in any appropriate way. Even a small cluster of 2 servers can process a relatively large volume of authorization request traffic. For such a cache to be effective, the state can be maintained for each transaction being serviced by the gateway  16 . A state service can be maintained across multiple web servers in a web cluster. Such a state service can be implemented in a shared server whereby each of the servers in the web cluster can access for the state information. Cache consistency and replication across multiple servers must be maintained for such an implementation. One specific implementation of such a state service is through the .NET framework provided by Microsoft Corporation, of Redmond, Wash. This framework supports a distributed computing environment in which applications may be written in any number of high level languages. The high level languages are compiled to a common runtime language known as CLR (Common Language Runtime). Further, in such an embodiment, the CLR can operate across various hardware platforms such that the implementation is hardware independent. In such an embodiment, the payment processing gateway  16  consists of a number of distributed computing systems. Objects can be used to exchange data between the systems and maintain. 
     In one implementation suitable for a small number of servers, each server maintains its own cache. A single server with sufficient processing capabilities may be capable of processing a substantial number of authorization requests. 
     The state service can operate with a database server, such as an SQL server which can be used to provide backup of stored data. The database can be used to restore the in-memory cache upon system failure of other fault. 
     In some embodiments, a single database access is employed for each authorization per transaction. For example, a procedure stored in the payment processing gateway  16  can be used to log the transaction to memory, for auditing, reporting, billing or other purposes. The same procedure used to log the data to the database can be used to read the associated cached invariant merchant data back from the database. 
     A web server front end can also be utilized with payment processing gateway  16  which directs web requests from a particular IP (Internet Protocol) address to the same server within the cluster. This particular redirection can be set for any time period, for example a number of days. Such a front end can be implemented in software or hardware components. With such an implementation, it is not necessary to synchronize the web server cache within the cluster. Instead, each web server within the cluster provided by the payment processing gateway  16  need only maintain state for the particular transactions which it is handling. 
     For small scale applications, a web service can be utilized such as that provided by ASP.NET. A particular ASP.NET page can be provided on each web server within the web cluster and used to update the cache of a given server. 
     A custom server can be provided which provides a state server to other computers within the cluster. The server can maintain an in-memory cache of merchant or store invariant records. The state server can respond to requests from the web cluster. If the state server is reset or otherwise looses data, the web cluster can provide a negative acknowledgement (i.e., NACK) to the merchant/store POS  12  thereby requesting that a complete data transmission be provided with the next transmission. The transmission of the complete data set can be provided for a desired length of time. This will cause the merchant to provide all of the merchant invariant data such that the database provided by the gateway  16  can be repopulated. During this period, the payment processing gateway  16  can provide the appropriate financial institution  20 A-N with all the data received from a particular merchant, mapping various fields as required. 
     In embodiments such as those discussed above in which various data is cached within a memory in payment processing gateway  16 , software operating at the point of sale device  12  can be configured to periodically transmit the entire data set for a given merchant to the payment processing gateway. This can be used to allow webservers or state servers of gateway  16  to be individually reset without difficulty. For example, the software running on a point of sale device  12  can be configured to submit a full data set every 2, 8 or 24 hours. Data transmissions such as the authorization response  230  shown in  FIG. 6  can include an additional data field to allow the payment processing gateway  16  to indicate that the full merchant data is required. Alternatively, a separate message can be sent by the gateway  16 . This data can be sent independently, or can be included in the next transaction request. Further, if only partial data is required, the message from the payment processing gateway  16  to the point of sale device  12  can indicate which data field or fields must be re-sent. In such a configuration, the payment processing gateway  16  can continue to accept partial data for a period of time after the initial request is sent. This allows multiple point of sale devices  12  within a store to transmit data to a payment processing gateway  16  which is implemented across multiple servers. 
     In order to further reduce the overhead of the messages exchanged across the public network  14 , or local networks of the retail location, in one aspect the present invention eliminates redundant or unrequired transmissions. For example, some acknowledgement messages used in socket-based protocols such as the protocol implemented by VisaNet are redundant. This is especially true for protocols based upon HTTPS. In one specific example, the acknowledgement (ACK) which is transmitted before a response for a credit card transaction in a single transaction mode is not required. Although the acknowledgement can be useful in monitoring operation of the software during debugging, it is not normally required by the point of sale device  12 . Other such non-essential transmissions can also be eliminated. 
     The various transmissions between the point of sale device  12  and the payment processing gateway  16 , including the authorization request  200  and the authorization response  230 , can be implemented using a number of techniques. For example, the HTTPS protocol can be used in which a packet or partial packet for transmission on a financial network  18 A-N is “wrapped” as the payload in the secure transmission. This configuration is particularly useful when integrating point of sale devices  12  which are at retail locations or which are implemented online through a merchant website. Further, this configuration can scale to high transaction volumes as required. 
     In another example, the payment processing gateway  16  provides an XML service for communication with the point of sale device  12 . This configuration is also well suited for integrating point of sale devices  12  which exist at both retail locations and from online merchants. 
     A secure socket layer (SSL) protocol can be used in which a particular message or packet is carried in an SSL wrapper. This implementation may be required for some debit card transactions and is suited for the high performance required to handle a large volume of transactions. Further, such a protocol can be used to keep a socket open on a financial network  18 A-N during the entire transaction process. Server clustering techniques such as thread pooling, clustering and load balancing can be implemented to support such an SSL protocol. 
     In another implementation of the present invention, the payment processing gateway  16  can provide a back end server process to maintain open payment sockets (or equivalents) through the financial networks  18 A-N. Such a back end service can be synchronized with a stateless front end coupled to public network  14 . Although credit card authorizations can typically be handled as a single synchronous transaction, debit card transactions typically require an additional final acknowledgement from the point of sale device  12  to the payment processing gateway  16  and to the appropriate financial institution  20 A-N over a financial network  18 A-N. This additional acknowledgement confirms that the retailer received the authorization acknowledgement and that the funds transfer was settled. If this acknowledgement is not received, the transaction is automatically reversed and the funds are returned to the customer&#39;s account. This can be implemented using a socket based protocol, such as SSL, where a server thread is used to maintain both the front end and back end socket sessions. However, this is more difficult to implement in a web based protocol which utilizes web servers such as Microsoft&#39;s IIS. As discussed above, web services are inherently stateless. Therefore, without additional implementation, the final acknowledgement may go to a different thread than the original transaction, and possibly even to a different server in a web cluster. In one aspect, the present invention maintains a thread in the web service such that such an acknowledgement can be sent to the appropriate financial institution. 
     The back end server process typically on a separate common server can be used to maintain an open back end socket over the appropriate financial network  18 A-N. In such an embodiment, the socket must be uniquely identified to the front end web server, for example using a GUID which the back end server maps to a specific socket port. The front end web server coupled to the public network  14  will place transaction messages on the appropriate queue. The queue is then accessed by the back end server process. The back end server process can be single or multi-threaded and processes messages by assigning them to a new or existing socket session as appropriate. A new socket session with a financial institute  18 A-N is opened at the start of each transaction and closed at the end of the transaction. All messages for a given transaction will occur over the same socket. Socket connections for incomplete transactions can be set to time out after a predetermined interval to protect server resources. 
     Although in typical payment processing systems, the point of sale device is required to provide an acknowledgement to the gateway during a debit card transaction, in one aspect, the present invention operates without the need for such a second acknowledgement. For example, the gateway can send a second acknowledgement back through the financial network without waiting for the acknowledgement to be received from the point of sale device. This allows the transaction to be stateless within the gateway and the debit transaction can then be easily supported over the HTTPS protocol without the need to use sockets such as SSL, directly. This configuration allows standard web servers to implement the present invention. Without the second acknowledgement from the point of the sale device, an additional safety mechanism can be provided to prevent a duplicate transaction from being processed. For example, the gateway can detect that the same or a similar transaction is being run from the same terminal or store within a specific period of time. If such a transaction is identified by the gateway, the gateway can simply block the transaction or send some type of a message back to the point of sale device indicating that an error has occurred or warning that a duplicate transaction has been received, request a confirmation that the duplicate data should be processed, request that the data be specifically called in, or simply acknowledge a successfully processed transaction previously. For example, if the same payment instrument is used from the same point of sale terminal within a relatively small time window, for example, one to two minutes, a simple acknowledgement can be provided. 
     Although the present invention has been described with reference to particular embodiments, workers skilled in the art will recognize that changes may be made in form and detail without departing from the spirit and scope of the invention. In one aspect, the present invention is configured to operate as a web service. In another aspect, a socket server implementation is used. In general, web services provide transactional functions which operate across a network such as the Internet. Web services adhere to a shared specification such that they are able to share objects and exchange data. One extension of web services which is well suited for implementation of the present invention is the web services enhancements (WSE) class library available in the Microsoft.NET framework. The present invention is applicable to electronic fund transfers based upon financial transaction authorization requests, and response to such requests. Although cards are specifically discussed, the invention relates to any type of payment instrument that can be used. The financial transaction authorization request are conveyed from a source, such as a store or merchant, to an authorization provider, such as a financial institution, over public and/or private networks or direct connections.