Abstract:
A method and system for delivering digital files in a peer-to-peer network comprising a plurality of nodes including at least one server is disclosed. The network includes a plurality of files that are available for accessibility by the nodes in which respective fingerprints are computed for each of the files based on content of the files. The method and system include partitioning each of the files into a plurality of file chunks, and assigning an error detecting code to each of the chunks. The file is then transmitted to a first node from at least one other node by transmitting the chunks of the file to the first node. The method and system further include computing a new error detecting code upon receipt of each chunk by the first node, and comparing the new error detecting code to the assigned error detecting code to verify that each chunk has been transmitted correctly, whereby the entire contents of the file does not have to be received before the first node discovers that the file is corrupt. In a further embodiment of the present invention, the method and system include determining the bandwidth contributed by each node that successfully transmitted a chunk of the file, and paying an owner of each node a fee based on the contributed bandwidth.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]    This application is a continuation-in-part of U.S. patent application Ser. No. 09/963,812, entitled “Method And System For Generating Revenue In A Peer-To-Peer File Delivery Network” (2060P), filed on Sep. 26, 2001, which is incorporated by reference herein. 
     
    
     
       FIELD OF THE INVENTION  
         [0002]    The present invention relates to an electronic marketplace for the buying and selling of digital files, and more particularly to method and system for delivering files in such a marketplace.  
         BACKGROUND OF THE INVENTION  
         [0003]    U.S. patent application Ser. No. 09/883,064, filed Jun. 15, 2001, assigned to the assignee of the present application, discloses a technique for accessing information in a peer-to-peer network. Each file accessible in the peer-to-peer network is assigned a respective hash ID or fingerprint ID which is used to describe the contents of that file. A conventional hash or fingerprinting algorithm analyzes the contents of a selected file and generates a unique hash ID or fingerprint ID that is used for identifying the specific contents of that file. The hashing algorithm is designed such that no two files having different file content will have the same hash ID. However, files having identical file content will have the same hash ID.  
           [0004]    Files in the peer-to-peer network are then identified and/or accessed based upon their associated hash ID values. In this way it is possible to identify identical files stored in the peer-to-peer network which have different file names and/or other metadata descriptors. Additionally, since the content of all files having the same hash ID will be identical, an automated process may be used to retrieve the desired content from one or more of the identified files. For example, a user may elect to retrieve a desired file (having an associated hash ID) which may be stored at one or more remote locations in the peer-to-peer network. Rather than the user having to select a specific location for accessing and retrieving the desired file, an automated process may use the hash ID (associated with the desired file) to automatically select one or more remote locations for retrieving the desired file.  
           [0005]    The automated process may choose to retrieve the entire file contents of the desired file from a specific remote location, or may choose to receive selected portions of the file contents of the desired file from different remote locations in the peer-to-peer network. Further, if an error occurs during the file transfer process, resulting in a partial file transfer, the automated process may be configured to identify the portion(s) of the desired file which were not retrieved, and automatically select at least one different remote location for retrieving the remaining contents of the desired file.  
           [0006]    Although retrieving portions of the file from different remote locations may speed the file transfer process, one disadvantage of the process is that it cannot be determined if the file is corrupt until all the portions of the file are received. For example, assume a user is downloading a movie and the movie is being retrieved in multiple portions from multiple locations. Only after all the portions of the movie are retrieved is an attempt made to reassemble the movie and generate a new fingerprint ID. The new fingerprint ID is then compared with the known fingerprint ID, and the movie is determined to be corrupt if there is no match. Certain portions of the file may also be corrupted by a hacker who intentionally sends corrupt file portions (e.g. a virus) to the unsuspecting user downloading the file. In either case, spending the time to download the entire contents of the file before determining it is corrupt is a waste of the user&#39;s time and network bandwidth.  
           [0007]    An additional disadvantage is that the peer nodes in a peer-to-peer network may be of different configurations and may have disparate network connection capabilities. In a public peer-to-peer network, for example, some peers may be home PC&#39;s with 56 k modem connections, while others may be high-speed corporate workstation with T3 connections. Consequently, some nodes in the network may be less reliable than others. With the current scheme for retrieving files in the network, there is currently no easy process for determining which peer nodes are producing the file transfer errors. Therefore, it is difficult to increase the overall reliability of the peer-to-peer network. An additional problem current peer-to-peer networks, is that there is no incentive to induce users to donate their peer devices to the network to serve files to other users.  
           [0008]    Accordingly, what is needed is an improved method and system for distributing digital files in a peer-to-peer network. The method and system should reduce the impact of file transfer errors, weed out unreliable peer nodes, and reward users who allow their peer devices to serve files, thereby increasing bandwidth of the network. The present invention addresses such needs.  
         SUMMARY OF THE INVENTION  
         [0009]    The present invention is a method and system for delivering digital files in a peer-to-peer network comprising a plurality of nodes including at least one server. The network includes a plurality of files in which respective fingerprints are computed for each of the files based on the content of the files. The method and system include partitioning each of the files into a plurality of file chunks, and assigning an error detecting code to each of the chunks. The file is then transmitted to a first node from at least one other node by transmitting the chunks of the file to the first node. The method and system further include computing a new error detecting code upon receipt of each chunk by the first node, and comparing the new error detecting code to the assigned error detecting code to verify that each chunk has been transmitted correctly. In a further embodiment of the present invention, the method and system include reporting and black listing nodes that committed errors, and determining the bandwidth contributed by each node that successfully transmitted a chunk of the file, and paying an owner of each node a fee based on the contributed bandwidth.  
           [0010]    According to the method and system disclosed herein, by assigning error detecting codes to each of the file chunks and verifying each chunk upon receipt means that the entire contents of the file do not have to be received before discovering that the file is corrupt, thereby reducing the impact of transfer errors. In addition, by paying owners who allow their computers to server files, the present invention provides an incentive for users to donate unused bandwidth of their computers to the network, thereby increasing overall bandwidth of the network. Bandwidth is further increased because a node can share a chunk with other nodes as soon as the chunk is received, rather than having to wait until the entire contents of the file are received. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0011]    [0011]FIGS. 1A and 1B are block diagrams illustrating a peer-to-peer (P2P) network architecture in accordance with one preferred embodiment of the present invention.  
         [0012]    [0012]FIG. 2 is a flow chart illustrating a method for generating revenue from the peer-to-peer network in accordance with one preferred embodiment.  
         [0013]    FIGS.  3 A- 3 E are flow charts illustrating the process for providing secure and reliable file sharing in a peer-to-peer network in accordance with a preferred embodiment of the present invention.  
     
    
     DETAILED DESCRIPTION  
       [0014]    The present invention relates to an electronic marketplace for digital files. The following description is presented to enable one of ordinary skill in the art to make and use the invention and is provided in the context of a patent application and its requirements. Various modifications to the preferred embodiments will be readily apparent to those skilled in the art and the generic principles herein may be applied to other embodiments. Thus, the present invention is not intended to be limited to the embodiment shown but is to be accorded the widest scope consistent with the principles and features described herein.  
         [0015]    The present invention provides a method for delivering files in a peer-to-peer network that reduces the impact of errors. The network enables secure and reliable peer-to-peer file sharing between client nodes where users may share content using both 1-to-1 and 1-to-many file transfers without the need for going through a server.  
         [0016]    [0016]FIGS. 1A and 1B are block diagrams illustrating a peer-to-peer (P2P) network architecture in accordance with one preferred embodiment of the present invention. The peer-to-peer network  10  includes a plurality of computers  18  interconnected over a public network, such as Internet, where some of the computers  18  are configured as server nodes  12 , and other computers  18  are configured as client nodes  14 . A client node  14  may represent a single computer or a proprietary network, such as AOL, or a cable network, for example, and in a preferred embodiment, the server nodes  14  are located worldwide.  
         [0017]    A computer  18  becomes a client node  14  by installing and running a P2P client application  22  designed for public networks that operates as described herein. In operation, the client application  22  allows the client node  14  to authenticate other client nodes  14  and to both receive content  20  and serve content  20 .  
         [0018]    Any combination of server nodes  12  and client nodes  14  may form extranets  16  that are protected by firewalls (not shown). As is well known in the art, an extranet  16  is basically a private network that uses the public Internet as its transmission system, but requires passwords to gain entrance.  
         [0019]    [0019]FIG. 1B is a diagram illustrating contents of the server nodes  12 . A server node  12  as used herein may refer to any computer that combines hosting services with databases. The server node  12  includes the file authority or query database  24 , the location database  26 , a fingerprint database  28 , a certificate database  30 , and a user database  32 . The query and a location databases  24  and  26  store the metadata and locations of the files shared on the network, respectively. The fingerprint database  28  stores fingerprint information that is generated for each file for determining the authenticity of the files. The certificate database  30  contains certificate information to certify and verify the authenticity of all users of the file network  10 . And the user database  32  includes account information for the users of the client nodes  14 .  
         [0020]    Through the servers  12 , the network  10  provides an online marketplace for digital files  20  that enables merchants to sell any digital content, and to have the content delivered to any appropriate digital electronic device. In one embodiment, the digital content takes the form of a single file, a copy of which is delivered to users that fulfill the payment rules instituted by the merchant. In a preferred embodiment, each server node  12  stores content  20  that comprises both commercial files  20   a  and noncommercial files  20   b.  Example types of files  20  may include audio files, video files, news articles and online magazines, image files, and confidential documents, for instance. In other embodiments, the file  20  itself is merely a token; for instance, a license key or a unique ticket number that allows the user access to a region of a web site, or, it may even denote permission to access a physical location, live event or even physical goods.  
         [0021]    When publishing a file  20  on the network  10 , the merchant or content owner identifies certain business rules for each item being sold. A unique identifier is then associated with each item sold or transferred via the network  10 . In a preferred embodiment, the identifier resembles an Internet URI (Uniform Resource Identifier), referred to herein as a YURI. Thus, when publishing the file  20 , the content owner defines all the rules associated with a YURI and uploads the file  20  to the server node  12 , preferably in XML format.  
         [0022]    The information about the file (e.g. size of the file, mime type, etc.), and the business rules (e.g. whether the file is a pay-per-view, the retail price, and so on) are stored in a query database  24  as metadata. Information about where the file  20  is available on the network  10  is preferably stored in the location database  26 . The query and location databases  24  and  26 , combined with payment and account functions, described below, enable the online marketplace for digital goods.  
         [0023]    Each file  20  published on the network  10  may be partitioned into chunks such that when a file  20  is to be downloaded to a particular node  14 , the chunks are downloaded from different nodes  14  in the network. According to one aspect of the present invention, each chunk of the file  20  is further assigned an error detecting code  35 . As the receiving peer node  14  receives each of the respective chunks of the file  20 , the receiving peer node  14  computes the error detecting codes  35  and compares them to the known error detecting codes  35  to detect errors in both the content and transmission of the file  20 . If an error is detected, resulting in a partial file transfer, the portion(s) of the file having the error is identified, and retransmitted from the same or different location. The node  14  causing the error is also reported to the sever  12  and will no longer be allowed to serve files if the number of errors it produces passes a predetermined threshold. Black listing nodes  14  in this manner increases the overall reliability of the network  10 .  
         [0024]    The server nodes  12  facilitate the file sharing process by performing a combination of the following functions. A first function of the server nodes  12  is to process search requests from the client nodes for files and to provide the results. A second function of the server nodes  12  is to aid the client nodes  14  in authenticating other client nodes  14  and file transfers during direct client-node transfers. A third function is content delivery, which includes a) providing subscription-based decentralized file downloads that allow the client nodes  14  to subscribe and automatically receive periodically updated files (push technology), and b) storing files when a client node  14  publishes a file for subsequent delivery to a requester by the server when the publishing node is off-line. A fourth function of the server nodes (and the client nodes) is to serve as proxies to the extranets so that the client nodes  14  inside the extranets can be part of the peer-to-peer network  10  through the extranet firewalls.  
         [0025]    [0025]FIG. 2 is a flow chart illustrating a method for generating revenue from the peer-to-peer network in accordance with one preferred embodiment. Revenue may be generated from the peer-to-peer network by providing a novel combination of file sharing services. One service provided for generating revenue is enabling peer-to-peer file sharing of content  20  in step  42 , and charging a fee based on the quantity of the data served in step  44 . As used herein, peer-to-peer file sharing refers to the initiation of a file download by a client node  14  from either the server node  12  or another client node  14 . Content made available for downloading in this manner may be referred to as “on demand” content because the content is available for downloading by the client nodes  14  at anytime. In a preferred embodiment, on demand content includes both fee-based content and free content. If the content downloaded is free to a user, then the provider of the content may be charged a fee for the serving of the content based on the quantity of the data transferred. If the content downloaded is fee-based, however, then the user of the initiating client node  14  may be charged the downloading fee.  
         [0026]    The second service provided for generating revenue in the network  10  is enabling decentralized downloads of subscription-based content in step  46 . According to one aspect of the present invention, client nodes  14  may subscribe to one or more of the subscription-based content, and in return, the subscribed to content is periodically sent to each the respective subscribing client nodes  14  either from the server node  12  or from another nearby client node  14 . Providers of the subscription-based content are then charged a fee for the serving the content to the client nodes in step  48 .  
         [0027]    In a preferred embodiment, the subscription-based content may be made available for free or for a fee (e.g., pay-per-view files). If the content if fee-based, then a fee may be charged to the users of the subscribing client nodes for receiving or opening the fee-based content. The fee charged to the users may be in addition to, or in lieu of, the fee charged to the providers of the subscription-based content. The fee charged to the content providers may be based on a priority level chosen for delivering the particular content, and the quantity of data delivered. A high priority means that the content will be allocated adequate bandwidth to deliver the file within a particular time frame and at the exclusion of other file deliveries if necessary.  
         [0028]    The third service provided for generating revenue in the network  10  is providing direct marketing to client nodes  14 , where marketing content, such as advertisements, are sent directly to the client nodes  14  from the server node  12  as well as from other client nodes  14  in step  50 . As user&#39;s become members of the network  10 , statistics are kept and provided to the marketing content providers for analysis. The providers may then specify which users should be targeted for which types of marketing content. A fee may then be charged to providers of the marketing content in step  52 .  
         [0029]    The fourth service provided for generating revenue and the network  10  is enabling client nodes  14  to become affiliate servers that deliver content to other client nodes  14  in step  54 . For example, college students that own computers and fast Internet connections may enroll as affiliate servers, thereby providing the network  10  with additional bandwidth to serve files. As an incentive, the owners of the affiliate servers may be paid a percentage of the fee charged for serving the files to the other client nodes  14  or a fixed fee in step  56 .  
         [0030]    FIGS.  3 A- 3 E are flow charts illustrating the process for providing secure and reliable file sharing in a peer-to-peer network in accordance with a preferred embodiment of the present invention. The process begins by allowing a user to become a member of the network  10  by downloading and installing a copy of the P2P client application  22  on the user&#39;s computer  18  in step  100 . In a preferred embodiment, the P2P client application  22  is downloaded from one of the server nodes  12 , although the P2P client application  22  may be obtained from other sources.  
         [0031]    Next, the server node  12  receives registration information entered by the user in step  102 , which can include billing information, e-mail address, and demographic information for direct marketing purposes. In response, the server node  12  generates account information for the user, including a digital certificate that includes a public key  36  and a private key  38  in step  104 . The user&#39;s account information, such as the user ID  39 , is stored in the user database  32 , and the user&#39;s public key  36  and private key  38  are stored in the certificate database  30  in step  106 . When registration is complete, the user is notified and may then execute the P2P client application  22  in step  107 . At any point during the registration process, the consumer may be requested to deposit a sum of money to his or her account, which will be used for fee-based file in which the fees are deducted from the consumer&#39;s account based on usage.  
         [0032]    Once the client node  68  invokes the client application  22 , a client application  22  browser window (not shown) is displayed on the computer in which the consumer may publish files  12  and search for files  12  on the network to download.  
         [0033]    The P2P client application  22  allows the consumer to both publish and share files over the network in step  108 , and download files over the network  10  in step  126 . The content owner  14  may share files  12  on the network in step  108  either publicly or privately. When publishing a file  12 , the content owner  14  specifies the business rules that are to be associated with file in step  109 . Examples of business rules include whether the item is to be sold via pay-per-download, the retail price to download the file, whether the file is available for subscription, and so on.  
         [0034]    In accordance with the present invention, secure and reliable file transfers are enabled by creating a fingerprint for each file when the file is published via steps  110 - 112 . First, the P2P client application  22  uses a conventional hash or fingerprinting algorithm to analyze the contents of the file and generate a bitstream ID  34  in step  109 . In a preferred embodiment, the bitstream ID  34  is generated by calculating binary values in data blocks of the file itself. The hashing algorithm is designed such that no two files having different file content will have the same hash ID. However, files having identical file content will have the same hash ID. Well-known one-way hashing algorithms that may be used include MD5 (Message Digest 5) and SHA-1 (Secure Hash Algorithm-1).  
         [0035]    The P2P client application  22  then uses the private key  88  to generate a digital signature  90  for the file in step  111 . In an alternative embodiment, the private key  88  may also be used to encrypt the bitstream ID.  
         [0036]    In a preferred embodiment, the bitstream ID  84 , the file information, and the digital signature  90  form the fingerprint for the file, thus ensuring that the file is transmitted in its original state (data integrity) by the identified consumer/publisher. In an alternative embodiment, only the bitstream ID  84  and optionally the file information may form the fingerprint for the file.  
         [0037]    After the fingerprint ID  84  has been generated for the file, in step  112 , the file is partitioned into separate portions called chunks. According to one aspect of the present invention, in step  114 , each chunk is analyzed and assigned an error detecting code  35 . As is well-known in the art, an error detecting code  35  is a bit or set of bits that are calculated as a function of the analyzed bits. There are many different kinds of error detecting codes  35  that may be used, including parity bit, longitudinal redundancy check, and cyclic redundancy check (CRC), for example. In a preferred embodiment, CRC 32  is used as the error detecting code  35 .  
         [0038]    After the error detecting codes  35  are assigned to the chunks, the business rules associated with the file, the fingerprint, and the error detecting codes  35  are uploaded to the server  12  in step  116 . In step  118 , the server stores the file information or metadata, information regarding the peer node  14 , the file fingerprint, and the error detecting codes  35  for the file chunks. Preferably, the server  12  stores the file information in the query database  24 , and stores peer node  14  information, such as the peer ID and bandwidth speed of the peer node  14  and the URL of the file on the peer node, in the location database  26 . The bitstream ID  84  and digital signature  90  may be stored in the fingerprint database  78  under an entry for the file.  
         [0039]    In step  120 , a copy of the file may also be uploaded to the server  12 . After the file data has been uploaded to the server  12 , in step  122 , the server  12  makes the file available to the public by posting a URL for the file&#39;s detail page on a website. Since the content owner usually chooses to make the file available from his own peer node, both URLs are entered into the location database  26  for the file. In step  124 , the server node  12  makes an entry in the location database  26  under the file for each node in the network  10  that the file is available from. All the entries in the query database  24  are also made available to a search engine to allow consumers to search for files  12  on the network in step  114  by entering search terms.  
         [0040]    In step  126 , the user may choose to download a particular file from the network. This can be done by the user web surfing and finding a link for a particular file of interest in step  128 , or by entering search terms into the server&#39;s search engine in step  130  and receiving in response a list of URL&#39;s for files having metadata in the query database  24  that match the search terms.  
         [0041]    In step  132 , the user clicks on one of the file URLs to download the file, which causes the client application  22  to initiate the download process. In step  134 , the client application  22  contacts the query database  24  to retrieve the meta-information, including the fingerprint and the error detection codes, and request all known sources for that fingerprint from the location database  26 . Note that the location database  26  maintains sources indexed by fingerprint, thus enabling multiple occurrences of a file—even if they are named differently—to all be treated as valid sources to ensure the quickest and most reliable download possible.  
         [0042]    In step  136 , the location database  26  responds with a list of known URLs, some of which may be inaccessible to the client application  22 . In step  138 , the client application  22  eliminates unreliable nodes, sorts the remaining sources by bandwidth speed, and begins to download distinct chunks from successive nodes on the list. Because faster nodes download chunks faster than slower nodes, the client application  22  dispatches new requests to these fast nodes. Finally, if some slow nodes still have not completed for filling the requests, the client application  22  closes the connection to the slow nodes and complete requests by redirecting unfinished request to the slow nodes. As soon as a chunk is successfully received, the node may report it to the server for the purpoe of serving the chunk to other nodes, even before all the chunks are received.  
         [0043]    In step  140 , the client application  22  records the bandwidth of each respective transmitting node as each chunk is being received. In step  142 , after receipt of each chunk, the client application  22  computes a new error detecting code  35  for the chunk and compares it to the assigned error detecting code  35  to verify that the chunk has been transmitted correctly. If the error detecting codes  35  of a particular chunk do not match in step  144 , the chunk is requested from a different node in step  146 , and the process continues at step  140 .  
         [0044]    In step  148 , once all the chunks have been received without error, the file is reassembled from the chunks. In step  150 , the client application  22  recomputes the fingerprint for the file and compares it with the fingerprint received from the server node  12  to verify that the file is an exact replica of the original file supplied by the content owner. In the embodiment where a public key is used to encrypt the fingerprint, the client application  22  also receives the public key from the server node  12 . The public key is used to decrypt the digital signature  90  in the fingerprint, and a new bitstream ID is generated and compared with the bitstream ID  84  in the fingerprint. If the digital signature is successfully decrypted and the two bitstream ID&#39;s match, then the file is authenticated. In the embodiment where the bitstream ID is encrypted, the encrypted bitstream ID in the fingerprint must be decrypted with the public key before the comparison. Fingerprinting files  12  as described herein allows the receiving node to determine the authenticity of both the file and the publisher.  
         [0045]    In step  152 , after the file has been successfully downloaded and verified, the client application  22  reports the results of the download to the server  12 , including which nodes served which chunks, the result of the transmission, the number of bytes received from each node, and the download time. In step  154 , the receiving peer node may then request that the server node  12  add an entry for the peer node into the location database  26 , thereby advertising itself as a new source for the file. The server node  12  may first inspect the peer node&#39;s address and makes a determination about whether this new source is behind a firewall or not.  
         [0046]    In step  156 , in response to a successful reported download, the server node  12  charges the client account of the consumer who downloaded the file, the fee associated with the file.  
         [0047]    According to a second aspect of the present invention, in step  158 , for each node that successfully transmitted a chunk of the file, the server  12  determines the bandwidth contributed (e.g., the number of bytes transmitted) and pays the owner of the node a fee based on the contributed bandwidth. By paying affiliates, the present invention provides an incentive for users to donate unused bandwidth of their computers to the network, thereby increasing overall bandwidth of the network.  
         [0048]    According to a third aspect of the present invention, in step  160 , the server  12  maintains an error report for each node and adds any errors found in the download results reported by the receiving peer node to the appropriate report. In step  162 , any reported errors that are older than a predetermined amount of time are deleted from the report to eliminate stale data. In step  164 , each node having a total number of reported errors that is greater than a predetermined threshold is designated by the server node  12  as ineligible to serve future file requests. Consequently, unreliable nodes are black listed and because they are not used to serve files, the impact of errors occurring on the network is substantially reduced, thereby increasing overall speed and reliability of the network.  
         [0049]    A method and system for efficiently delivering digital files in a peer-to-peer network has been disclosed. Although the present invention has been described in accordance with the embodiments shown, one of ordinary skill in the art will readily recognize that there could be variations to the embodiments and those variations would be within the spirit and scope of the present invention. For example, a file that is being published on the network may be partitioned into chunks and the chunks assigned error detecting codes by the server rather than the publishing peer node. Accordingly, many modifications may be made by one of ordinary skill in the art without departing from the spirit and scope of the appended claims.