Patent Publication Number: US-8542582-B2

Title: Confirmation of delivery of content to an HTTP/TCP device

Description:
This application is a continuation of application Ser. No. 10/739,555, filed Dec. 17, 2003, now issued U.S. Pat. No. 7,911,994, which claims the benefit of U.S. Provisional Patent Application No. 60/451,297, filed on Feb. 28, 2003, and entitled, “Confirmation of Delivery of Content to an HTTP/TCP Device,” which is incorporated herein by reference. 
    
    
     FIELD OF THE INVENTION 
     This invention relates to the field of wireless communication. In particular, this invention relates to confirmation of data delivery to a client from a proxy or a server of a wireless carrier network without a specific indication from the client. 
     BACKGROUND 
     Electronic-commerce (e-commerce) has become increasingly important in today&#39;s society. People make purchases online using their personal computers (PCs), laptop PCs, Personal Digital Assistants (PDAs), cellular phones, etc. In particular, people may purchase text, icons, video, music, and other intangible content that is delivered to their mobile communication device upon request. Usually, the request for the content and the response are sent using Hypertext Transfer Protocol (HTTP). 
     Typically, the HTTP response is transmitted between systems implementing transfer control protocol (TCP). When an HTTP-based application writes data of the HTTP response to a TCP socket provided by an operating system using one of a range of write commands, the data is placed in a TCP send buffer for that socket, and the write command returns. In general, the fact that the write command has returned merely indicates that the data has been written to the TCP send buffer, and a returning write command does not confirm that the data has been sent to the TCP receiving stack. 
     Upon receipt of the data, the TCP receiver transmits one or more acknowledgments to the sender to indicate the successful receipt of the data segments. The TCP receiver sends a final acknowledgment, also referred to as the last ACK signal, to the TCP sender indicating the receipt of the final segment of data. However, the standard TCP socket Application Programmer&#39;s Interface (API) does not provide an indication of the receipt of the last ACK signal to the sending application to confirm the successful receipt of the data by the TCP receiver. 
     With prior technology, there is no way of telling at the HTTP level that the HTTP response has been delivered successfully to the requester, i.e., the HTTP client. HTTP typically does not include any feature to allow an HTTP client to confirm the receipt of the HTTP response with the server or a proxy that sends the HTTP response. However, where a communication carrier wishes to charge the user for the receipt of the data or content in the HTTP response, the ability to determine that the HTTP response has been delivered successfully is important for billing customers on such services correctly. 
     At least two potential solutions to the above problem are unsatisfactory. One solution proposes to extend HTTP to support functionalities via which the client may indicate the successful receipt of the HTTP response. Such additional functionalities would have to be successfully adopted by the relevant standard setting bodies to ensure that the future HTTP-compatible devices support the additional functionalities. 
     Another potential solution is to modify the TCP stack to capture the last acknowledgement of the transmission of the HTTP response, and to extend the standard TCP API to allow the TCP stack to indicate data delivery to the sending HTTP-based application. However, since most TCP stacks are shipped with an operating system, it is difficult, if not impractical, to modify the TCP stacks. Moreover, generating a separate TCP stack in addition to the TCP stacks shipped with the operating system by a service provider is time consuming as well as impractical. 
     SUMMARY 
     A method to confirm delivery of data to a receiving device via a sending socket is disclosed. One embodiment of the method comprises determining when a predetermined amount of data has been removed from a send buffer of the sending socket and sending a confirmation when the predetermined amount of data has been removed from the send buffer. 
     In a specific embodiment of the present invention, the sending socket implements transport control protocol (TCP). 
     Other features of the present invention will be apparent from the accompanying drawings and from the detailed description that follows. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention is illustrated by way of example and not limitation in the figures of the accompanying drawings, in which like references indicate similar elements and in which: 
         FIG. 1  illustrates one embodiment of a wireless communication system to provide confirmation of data delivery; 
         FIG. 2  illustrates a flow diagram of one embodiment of a process to confirm data delivery from a carrier network to a client device; and 
         FIG. 3  illustrates an exemplary embodiment of a wireless communication system. 
     
    
    
     DETAILED DESCRIPTION 
     In the following description, numerous specific details are set forth. However, it is understood that embodiments of the invention may be practiced without these specific details. In other instances, well-known circuits, structures, and techniques have not been shown in detail in order not to obscure the understanding of this description. 
     Reference in the specification to “one embodiment” or “an embodiment” means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the invention. The appearances of the phrase “in one embodiment” in various places in the specification do not necessarily all refer to the same embodiment. 
     Some portions of the following detailed description are presented in terms of algorithms and symbolic representations of operations on data bits within a computer memory. These algorithmic descriptions and representations are the tools used by those skilled in the data processing arts to most effectively convey the substance of their work to others skilled in the art. An algorithm is here, and generally, conceived to be a self-consistent sequence of operations leading to a desired result. The operations are those requiring physical manipulations of physical quantities. Usually, though not necessarily, these quantities take the form of electrical or magnetic signals capable of being stored, transferred, combined, compared, and otherwise manipulated. It has proven convenient at times, principally for reasons of common usage, to refer to these signals as bits, values, elements, symbols, characters, terms, numbers, or the like. 
     It should be borne in mind, however, that all of these and similar terms are to be associated with the appropriate physical quantities and are merely convenient labels applied to these quantities. Unless specifically stated otherwise as apparent from the following discussion, it is appreciated that throughout the description, discussions utilizing terms such as “processing” or “computing” or “calculating” or “determining” or “displaying” or the like, refer to the action and processes of a computer system, or similar electronic computing device, that manipulates and transforms data represented as physical (electronic) quantities within the computer system&#39;s registers and memories into other data similarly represented as physical quantities within the computer system memories or registers or other such information storage, transmission or display devices. 
     The present invention also relates to apparatus for performing the operations described herein. This apparatus may be specially constructed for the required purposes, or it may comprise a general-purpose computer selectively activated or reconfigured by a computer program stored in the computer. Such a computer program may be stored in a computer readable storage medium, such as, but is not limited to, any type of disk including floppy disks, optical disks, CD-ROMs, and magnetic-optical disks, read-only memories (ROMs), random access memories (RAMs), EPROMs, EEPROMs, magnetic or optical cards, or any type of media suitable for storing electronic instructions, and each coupled to a computer system bus. 
     The processes and displays presented herein are not inherently related to any particular computer or other apparatus. Various general-purpose systems may be used with programs in accordance with the teachings herein, or it may prove convenient to construct more specialized apparatus to perform the operations described. The required structure for a variety of these systems will appear from the description below. In addition, the present invention is not described with reference to any particular programming language. It will be appreciated that a variety of programming languages may be used to implement the teachings of the invention as described herein. 
     A machine-readable medium includes any mechanism for storing or transmitting information in a form readable by a machine (e.g., a computer). For example, a machine-readable medium includes read only memory (“ROM”); random access memory (“RAM”); magnetic disk storage media; optical storage media; flash memory devices; electrical, optical, acoustical or other form of propagated signals (e.g., carrier waves, infrared signals, digital signals, etc.); etc. 
       FIG. 1  illustrates one embodiment of a wireless communication system to provide confirmation of data delivery. The system  100  includes a device  110  of a carrier network, a sending socket  120  having a send buffer  122  and a stack  123 , a receiving socket  130  having a receive buffer  132  and a stack  133 , and a client device  140 . The device  110  may include a proxy or a server. Therefore, in the following description, the device  110  is also referred to as a proxy/server  110 . The client device  140  may be a mobile communication device, such as a cellular phone, a pager, a PDA, etc. 
     Different embodiments of the system  100  may implement various protocols to transmit data. For instance, the system  100  may implement a version of transmission control protocol (TCP) without a specific acknowledgement mechanism. Then the stacks  123  and  133  in the system  100  may be TCP stacks. Examples of operating systems providing TCP stacks include Solaris from Sun Microsystems, Inc. (Santa Clara, Calif.), AIX from International Business Machine Corporation (Armonk, N.Y.), etc. TCP stacks typically provide a standard API for managing and using sockets. Although the following description is directed to an exemplary system implementing TCP, one should appreciate that the invention is not necessarily limited to TCP. 
     In one embodiment, an HTTP-based application  112  of the device  110  of the carrier network sends data to the client device  140 . The HTTP-based application  112  may send the data in response to a request from an HTTP-client application  142  of the client device  140 . 
     The HTTP-based application  112  transmits data by writing the data onto a sending socket using an appropriate API command, such as Writen or Write for a TCP socket. The act of writing the data to the sending socket  120  causes the data to be placed into the send buffer  122  rather than sending the data directly to the TCP receiving socket  130  of the client  140 . The TCP sending socket  120  retrieves the data from the send buffer  122  and transmits the data via the TCP stack  123  to the TCP receiving socket  130  of the client device  140  according to the rules defined in TCP. Upon receipt of the data at the receiving TCP stack  133 , the data is placed in the TCP receive buffer  132  so that the data becomes available to the HTTP-client application  142 , Then the TCP receiving socket  130  sends acknowledgements to the TCP sending socket  120  to indicate the receipt of the data. The TCP sending socket  120  may deliver the data to the TCP receiving socket  130 , possibly in multiple segments, and possibly with retransmissions, according to the rules of TCP. 
     In one embodiment, the TCP send buffer  122  is monitored to determine when the TCP sending socket  120  has removed substantially all of the data from the TCP send buffer  122 . The TCP sending socket  120  removes data from the TCP send buffer  122  when the data has been successfully delivered to the TCP receiving socket  130 . Thus, by determining when the TCP sending socket  120  has substantially cleared the send buffer  120 , it can be inferred that the client device  140  has successfully received the data. 
     In order to determine when the TCP send buffer  122  has been substantially cleared, a confirmation delivery application of the proxy/server  110  may determine the size of the TCP send buffer  122  utilizing socket options. The confirmation delivery application may be part of the HTTP-based application  112  or a software module substantially independent of the HTTP-based application  112 . The confirmation delivery application sets a threshold, also referred to as a “low water” mark, to be substantially equal to the size of the TCP send buffer  122 . Therefore, the “low water” mark essentially defines how much space there should be in the send buffer  122  in order for the send buffer  122  to be considered available for writing. The send buffer “low water” mark may be used with the select command of the socket API such that the select command returns to the HTTP-based application  112  when the available space of the send buffer  122  reaches the “low water” mark. 
     Alternatively, the “low water” mark may be set by other mechanisms, such as by setting the configuration parameters that may apply to a single socket, one or more predetermined groups of sockets, or all sockets in the system. For instance, the configuration parameter for the “low water” mark may be set to a particular value such that when a new socket is created, the new socket gets a value based on the configuration parameters by default as the socket&#39;s “low water” mark; thus, the value of the “low water” mark may not be specified explicitly each time a socket is created. However, one should appreciate that the default may be overridden in some embodiments, and thus, the “low water” mark of a new socket may be set explicitly when the new socket is created. 
     As discussed above, the data is placed in the TCP send buffer  122  upon writing the data to the sending socket  120 . Then the confirmation delivery application running on the proxy/server  110  issues a command against the sending socket  120 , such as the select command of the socket API. In one embodiment, the select command returns when the available space in the send buffer reaches the send buffer “low water” mark. Since the value of the send buffer “low water” mark is substantially equal to the size of the send buffer  122 , the select command returns when the send buffer  122  is substantially empty, thus indicating that the data written to the send buffer  122  has been delivered to the receiving TCP stack  133 . However, in some embodiments, other TCP socket API commands may be used to determine when the TCP send buffer  120  has been substantially cleared in order to enable confirmation of data delivery. 
       FIG. 2  illustrates a flow diagram of one embodiment of a process to confirm data delivery from a carrier to a client device. The process is performed by processing logic that may comprise hardware (e.g., circuitry, dedicated logic, etc.), software (such as the confirmation delivery application discussed above) running on a general-purpose computer system or a dedicated machine (e.g., the proxy/server  110  in  FIG. 1 ), or a combination of both. 
     Processing logic first determines the size of a send buffer of a sending socket (processing block  210 ). Then processing logic sets a threshold, also referred to as a “low water” mark, substantially equal to the size of the send buffer (processing block  220 ). To send data from the carrier, processing logic writes the data to the send buffer (processing block  230 ). Processing logic issues a command against the sending socket such that the command returns when the available space in the send buffer reaches the threshold (processing block  240 ). In one embodiment, the carrier network implements TCP. The command issued against the sending TCP socket is a select command of the socket API. 
     One advantage of using an existing TCP socket API command is to provide compatibility with the existing TCP devices in the market. The use of the existing TCP socket API command also reduces the overhead in data transmission by avoiding the addition of more messages to the protocol in order to support specific acknowledgement. Moreover, using the existing TCP socket API command does not increase traffic on the network, which is particularly important for mobile communication. 
       FIG. 3  illustrates an exemplary embodiment of a mobile communication system in which the invention can be implemented. The system  300  includes a wireless carrier network  310 , a proxy/server  315 , a number of TCP sockets  320 , and a number of mobile communication devices  330 . The wireless network  310  sends data via the proxy/server  315  to one of the mobile communication devices  330  using one of the TCP sockets  320 . The TCP sockets  320  may be bidirectional. For the purpose of illustration, it is assumed that the data is sent to the receiving mobile communication device  332  in the following description. In one embodiment, the mobile communication device  332  sets up a TCP link with the proxy/server  315 . As a result, a first socket is created at the proxy/server  315  end of the link for the proxy/server  315 . The proxy/server  315  may use the first socket to send or receive data from the mobile communication device  332 . Likewise, a second socket is created at the other end of the link for the receiving device  332 , which may use the second socket to send or receive data from the proxy/server  315 . 
     To enable confirmation of data delivery to the proxy/server  315 , a confirmation delivery application running on the proxy/server  315  first determines the size of the send buffer of one of the TCP sockets  320 , hereinafter referred to as a sending socket. Then a threshold, also referred to as a “low water” mark, is set to be substantially equal to the size of the send buffer. After writing data to the send buffer of the sending socket, the confirmation delivery application issues a command against the sending socket. The command issued may be a select command of the socket API. 
     When the available space of the send buffer reaches the threshold, the select command is returned to the proxy/server  315 . Since the threshold is substantially equal to the size of the send buffer and the available space of the send buffer reaches the threshold, therefore, the send buffer is substantially empty. Given that the sending socket removes data from the send buffer when the acknowledgement of data receipt is received from a receiving socket, which is one of the TCP sockets  320 , one can infer from the substantially empty send buffer that the receiving socket has received substantially all data written into the send buffer. Therefore, when the select command is returned to the proxy/server  315 , the confirmation delivery application can confirm that the receiving socket of the mobile communication device  332  has received the data. 
     Being able to confirm data delivery allows the wireless carrier network  310  to provide more reliable communication services to the mobile communication devices  330 . Furthermore, the ability to confirm data delivery helps the network carrier to correctly bill the users of the client devices  330  for the data or content delivered, which is important for customer satisfaction. 
     Although the present invention has been described with references to specific exemplary embodiments, it will be evident that various modifications and changes may be made to these embodiments without departing from the broader spirit and scope of the invention as set forth in the claims. Accordingly, the specification and drawings are to be regarded in an illustrative sense rather than a restrictive sense.