Abstract:
A computer method and related apparatus for delivering content files to a client computer are disclosed wherein a request for a content file on a content server is received from a client; a future time period during which the content file will be available on a cache server is determined; and a rewritten uniform resource locator comprising time period availability information, or a link to a file comprising the time period availability information, is returned from the server to the client. The client can use the information to obtain the content file in the determined future time period.

Description:
BACKGROUND ART 
       [0001]    This invention relates to the field of data communications and especially to methods and systems for delivering content files efficiently. The invention relates in particular to methods and systems for requesting, storing, and delivering large and very large content files from a remote content provider to a content file client device such as a laptop computer using a browser, a personal data assistant, or a cell phone. 
         [0002]    Multimedia digital information files such as audio, video, movies, and the like are relatively large as compared to most other types of files which are downloaded via the Internet. Frequently a request is made from a client computer to a content provider web site and the large file is not immediately available due to network congestion, too much current traffic, prioritizations, and capacity limitations. 
         [0003]    Among the previously proposed and used methods and systems for delivering content in general to client computers are content delivery networks which include content brokers and edge servers, which are a form of cache servers located in strategic geographic locations. Content delivery networks can cache content in cache servers, known in such networks as edge servers because they are located at strategic geographic locations near the edge of the network, from which content can be available to client computers even in cases of network congestion and outage. 
         [0004]    Various techniques are described in an Akamai Networks, Inc. White Paper entitled  Internet Bottlenecks: the Case for Edge Delivery Services , and a Network Working Group Internet Draft of Apr. 3, 2003 entitled  Known CN Request - Routing Mechanisms , Barbir, et al. 
         [0005]    Content delivery networks are also described in U.S. Patent Publications 20030065762 of Apr. 3, 2003; 20030002484 of Jan. 2, 2003; and Leighton et al, U.S. Pat. No. 6,108,703. The method of tagging content for delivery from the content delivery network using a migratory and a rewrite tool which rewrites URLs to point to the edge server most likely to host the requested content is disclosed in these publications and patent. 
         [0006]    Other content delivery type networks for television broadcasting, live performances, music juke boxes, global networks and data delivery systems are described in the following references: International Publication No. WO 03/034704 published Apr. 24, 2003; U.S. Patent Publication No. 2002/0026512 ; “The Interactive Multimedia Jukebox  ( IMJ ):  a new paradigm for the on - demand delivery of audio/video ”, Kevin C. Almeroth, Mostafa H. Ammar, Computer Networks and ISDN Systems 30 (1998) 431-441, 1998; U.S. Pat. No. 6,108,703; and International Publication No. WO 02/08856 published Jan. 31, 2002. 
         [0007]    Prior content delivery networks distribute content based on past, i.e., historical, information. Obtaining content availability information from content delivery-networks, a content provider can redirect a content uniform resource locator (URL) to an edge server that is closer to the requesting client in order to speed up) the downloading of the content file to the client. The content provider may fail to redirect a content URL to an edge server closer to requesting client because the content is not currently available on any of those edge servers. In some cases a user will be willing to tolerate delays in delivery of large content files such as multimedia files for a variety of reasons, for example the user may not need to use the file immediately or may be requesting the file from a personal data assistant or web-enabled cellular phone and may wish to have the file streamed at a future time because of time constraint or may not be able to use the file because of capacity constraint of the requesting device. 
         [0008]    In a downloading service model, for example, a content request does not necessarily reflect that there is an immediate need for the content. Therefore, even if a piece of content is currently not available on an edge server, if the content delivery network can deliver the content to the edge server at a future time, the content provider can satisfy the need of a user by redirecting the request to the edge server. 
         [0009]    While present content delivery networks improve the delivery of content files to client computers, as content files become larger and use of the Internet to request and obtain multimedia files becomes more prevalent, further improvements to content delivery systems and methods are needed to provide a satisfactory delivery rates. 
       BRIEF SUMMARY OF THE INVENTION 
       [0010]    The present invention addresses the aforementioned needs by providing a method delivering content files to a client computer comprising receiving a request for a content file from a client; determining a future time period during which the content file will be available on a cache server; and delivering time based information on content availability. 
         [0011]    In another aspect, the invention comprises a system for delivering content files to a client computer comprising a content server and at least one cache server adapted to: (a) receive a request for a content file from a client, (b) determine a future time period during which the file will be available for delivery from the content server or a cache server, and (c) to return time-based information comprising the time period availability information. 
         [0012]    By way of example, the time-based information can comprise a URL rewritten according to methods generally known in this art, for example by a content broker which receives information from the cache servers in a content delivery network as to traffic, availability of particular files and various locations, and then returns the re-written URL to the content server which received the request from the client. The rewritten URL contains time period information or a link to a file comprising time period availability information, and preferably also comprises or points to information regarding the content server or cache server on which the content will be available during the time period. In place of a re-written URL, the time information could also comprise one of a CGI script or an active X program. 
         [0013]    The present invention enables extending request routing capability to cache servers, which can hold content at a future time period. For example, Akamai&#39;s request routing technique is to replace the original URL (e.g. http://contentURL) with an “Akamai-ed” URL (e.g. http://local_cache_server/contentURL) that redirects to a local cache server in the content delivery network. In accordance with an aspect of the invention, an “Akamai-ed” URL is a link that will be available during a future time period. 
         [0014]    The client computer can be any general purpose or special purpose computer such as a desktop, laptop, personal data assistant, web-enabled cellular phone, or any other Internet Protocol enabled machine, usually of the type, which is running any Mosaic-based web browser such as Internet Explorer, or Netscape. The client usually has plug-ins, a term well known in this art for additional programs which carry out separate functions. 
         [0015]    By use of URLs or other comparable mechanisms, the client computer can open web pages and request content files to be transferred or downloaded. The web pages and content files are initially stored at a content server, which runs a web site, but may also be stored in various edge servers in a content delivery network, which comprises a broker, to communicate with content servers. Base on the location and delay tolerance of the request from the client computer, a content server can provide a redirected URL comprising a time period of availability of the corresponding content. The delay tolerance can be, for example, “no later than 6 PM” or “best effort,” for example. 
         [0016]    As is conventional with content delivery networks, the content files are stored in a content server computer and copies of the content files are delivered from time to time to one or more edge servers, and wherein upon receipt of a request for a content file, the server either delivers the content file to the client, redirects the request to an edge server which has a copy of the requested content file by sending to the requesting client a rewritten URL. In accordance with an aspect of the invention, the rewritten URL comprises the timing availability information, or a link to a file comprising the time period availability information. 
         [0017]    The content server and/or the content delivery network determine the future availability information. In one embodiment, the content server communicates with the content delivery network through a broker. 
         [0018]    The request from the client for a file can comprise delay tolerance information, which can be generated at the client level by any of several methods, for example, standard preferences may be indicated in a web browser, or the client indicates at the content server web site with a desired delivery time or a desired delivery time period. 
         [0019]    The rewritten URL returned to the client may comprise a special string as indicating the time period availability information, or the URL itself is a link to a file comprising the redirected URL and the time period availability information, for example, the file contains XML tags comprising the time period so that an XML parser can read the XML tag and enable or disable the URL during the appropriate time periods. 
         [0020]    The revised URL can also link to a program on a content server or a cache server, which can transfer, i.e., push or stream, the requested content file during the time period or at a certain time. 
         [0021]    Alternatively, as mentioned, the client may have a plug-in or other programming to process the revised URL and request transfer of the content file during the period of availability. 
         [0022]    The content delivery network, which typically comprises at least one edge server and broker(s) to communicate with the content server(s), can schedule the distribution of content files to edge servers and return a corresponding URL with availability time period information to content server through a broker. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0023]      FIG. 1  is a schematic of an embodiment of a system of the invention. 
           [0024]      FIG. 2  is a flow chart of one embodiment of the invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0025]      FIG. 1  depicts a content delivery network in accordance with the present principles. The network includes a client that runs a browser  21 . The browser  21  operates to request a content file, for example the movie entitled “Matrix Reloaded,” by sending a URL  28  to a content provider  22 , Movies-Inc.Com in this example. Movies-Inc.Com content provider  22  web site has a business relationship with the content delivery network to speed up the delivery of movie files, which are relatively large to its customers, such as client  21 . Movies-Inc.Com content provider  22  sends a request  34  for information to a content delivery network broker  25 , which manages at least one, and preferably, a set of cache servers, exemplified by cache server  23  and cache server  24 . The broker  25  sends availability inquiries  31  and  36  to the cache servers  23  and  24 , respectively, to find out whether they currently store the requested movie file. Various movie files are transferred from time to time from the content provider  22  to cache servers  23  and  24  via the broker  25 . 
         [0026]    The broker  25  provides content current and/or future availability information to Movies-Inc.Com content provider  22  where the content file URLs are prepended (Akamai-ed) for redirecting to cache servers. Additionally, information on the time periods when the content files will be available at corresponding cache servers is also added. Upon receiving a content request from the client  21 , the Movies-Inc.Com content provider  22  can also dynamically request the broker  25  for a content file delivery to a location close to the client. Based on the capacity of network links and cache servers, a content delivery schedule can be made by the content delivery network and the content file availability can be returned to the Movies-Inc.Com content provider  22  through the broker  25 . 
         [0027]    A prepended URL directed to cache server  23  can be redirected to cache server  24  if the cache server  23  determines that the cache server  24  is closer to the client and the content file is available during a time period satisfying the client. 
         [0028]    The rewritten URL may contain timing information in some of the following formats: (a) XML tags, (b) parameters of a cache server, or (c) client dynamic programs, respectively, as illustrated in the following three examples. 
       EXAMPLE 1 
     XML Tags 
       [0029]    In this case, the URL link is enabled according to timing tags. For example: 
         [0000]    
       
         
               
               
             
           
               
                   
                   
               
             
             
               
                   
                 &lt;Content timing&gt; 
               
               
                   
                 &lt;Period start=18:00, 9/10/03, end=19:00&gt; 
               
               
                   
                 &lt;a href=http://location1/contentURL&gt; contentURL &lt;/a&gt; 
               
               
                   
                 &lt;/Period&gt; 
               
               
                   
                 &lt;Period start=19:00, 9/10/03. end=20:00&gt; 
               
               
                   
                 &lt;a href=http://location2/contentURL&gt; contentURL &lt;/a&gt; 
               
               
                   
                 &lt;/Period&gt; 
               
               
                   
                 &lt;/Content timing&gt; 
               
               
                   
                   
               
             
          
         
       
     
         [0030]    An XML parser can interpret these tags and can enable/disable the link during different time periods. The XML parser may use, for example, a different color or shade for a disabled link and show available time period when the mouse is on it, for example. 
       EXAMPLE 2 
     Server Program Parameter 
       [0031]    In this example, the URL link points to a CGI or other type of server program on the original or local server, with parameters of both URL and time period. For example: http://contentTiming.cgi?URL-contentURL?period start=1800?period_end=1900). If the current time does not fall in the given time period, the CGI program will do nothing but return to current page. Otherwise, opening a returned URL (e.g. http://local_cache_server/contentURL) serves to accomplish content downloading. 
         [0032]    Similar to the XML example, this one requires the browser understand special strings in the parameter field of the URL. The browser can disable the URL when current time is out of the range. 
       EXAMPLE 3 
     Client Plug-In 
       [0033]    In this method, the URL link is pointing to a file with a special extension; for example, .tim (http://contentURL.tim). In the file “contentURL.tim”, the original and local URL and timing information can be available in a format that is readable by the plug-in program. This solution has the most flexibility. The plug-in program can run in background to get the content at a future time without any interaction. 
         [0034]    Content timing is a useful tool to extend existing content delivery network (content delivery network) technologies to work for downloading services. In a downloading service model, the locations and the devices of the content consumer and the content requester can be different, which is known as the triangle model with respect to traditional server/client model. 
         [0035]    The three examples alluded to earlier can be used for both the server/client model and the triangle model as long as the URL link can be viewed by the client. 
         [0036]    The future information of a content availability depends on the scheduler of content distribution in a content delivery network network. Scheduling content to be made available at the cache server is a separable problem from our current methods of indicating time availability of the content. 
         [0037]      FIG. 2  depicts a flow chart illustrating the steps undertaken by the content delivery network of  FIG. 1  to schedule content delivery in accordance with the present principles. The method commences upon receipt of a request for content from a client using the browser  21  of  FIG. 1  during step  100  of  FIG. 2 . A check occurs at the request-routing functional entity (RRFE) during step  120 , based on the location of the client, regarding whether the content is currently available on a cache server (e.g., cache server  23 ) closest to the client. If so, a prepended URL redirecting to cache server  23  of  FIG. 1  is returned to the client by the RRFE during step  130  of  FIG. 2 . If the content isn&#39;t available from the cache server  23  following the check made during step  120 , a check occurs at the RRFE during step  140  of  FIG. 2  to determine if the requested content file is scheduled to be available on another cache server close to the client, e.g., cache server  24  of  FIG. 1 . If so, a prepended URL with a future availability [T1, T2], redirecting to the cache server  24  of  FIG. 1  is returned by the RRFE during step  150  of  FIG. 2 . When the client receives the prepended URL, it requests the content file from the appropriate cache server when the content is available. 
         [0038]    If the content file is not immediately available and there is no scheduled availability on any of the cache server close to the client, the content server  22  will negotiate with the content delivery network (CDN) through the broker  25  in order to determine the start time, end time, and the cache server where the content file will next be available during step  160  of  FIG. 2  and return a URL redirecting to such cache server with the time period information during step  170 . The client will process the URL and wait until the time period to request the file from the appropriate cache server. 
         [0039]    The scope of the invention is defined by the appended claims.