Abstract:
A method for communicating information between a public server and a private server, where the public server is unable to initiate communication with the private server. The method includes indirectly notifying the private server to poll the public server.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    The present invention relates generally to network communications, and, more particularly, to indirectly notifying a private server to poll a public server beyond a firewall between the private server and public server, where the firewall prevents the public server from directly contacting the private server.  
           [0003]    2. Description of Related Art  
           [0004]    Increasingly, information is distributed across many communication devices (combination of storage and servers) some of which reside on one side of a firewall (private or trusted) and some of which reside on another side of the firewall (public). Often a device on the public side of the firewall possesses information that is desired by a device on the private side but the device on the public side is not able to initiate communication with the private side device in order to send the information to it. Consequently, the private side device is often designed to periodically poll the public side device to discover if there is information for it. If the polling interval is small and information is often not present, processor time and communications resources are wasted. If the polling interval is large and information often has to wait a long time before it is sent, the information is not received at the private side device in a timely manner. Moreover, these solutions typically are unable to give a user immediate feedback that a private side device has received information from the public side device that is related to the user.  
           [0005]    Another common approach is to open a hole in the firewall to allow traffic from specific public side devices to be delivered to the private side devices. This approach presents security risks, and is, thus, undesirable.  
           [0006]    Thus, there is a need for mechanisms for communicating information between a public side device and a private side device without requiring inefficient or untimely polling, or holes in a firewall. The present invention meets this need.  
         SUMMARY OF THE INVENTION  
         [0007]    A method for communicating information between a public server and a private server, where the public server is unable to initiate communication with the private server, is described. The method includes indirectly notifying the private server to poll the public server. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0008]    The present invention is illustrated by way of example, and not limitation, in the figures of the accompanying drawings in which like references denote similar elements, and in which:  
         [0009]    [0009]FIG. 1 illustrates a communication system according to one embodiment of the present invention.  
         [0010]    [0010]FIG. 2 illustrates a communication system according to another embodiment of the present invention. 
     
    
     DETAILED DESCRIPTION  
       [0011]    Methods and apparatus for securely, efficiently, and timely communicating information between a public side device and a private side device are described. In the following description, for purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of the present invention. It will be evident, however, to one skilled in the art that the present invention may be practiced in a variety of networks, especially transport control protocol (TCP) and hypertext transfer protocol (HTTP) networks, without these specific details. In other instances, well-known operations, steps, functions and elements are not shown in order to avoid obscuring the invention.  
         [0012]    Parts of the description will be presented using terminology commonly employed by those skilled in the art to convey the substance of their work to others skilled in the art, such as firewall, private server, public server, client machine or device, protocol, HTTP request and so forth. Various operations will be described as multiple discrete steps performed in turn in a manner that is most helpful in understanding the present invention. However, the order of description should not be construed as to imply that these operations are necessarily performed in the order that they are presented, or even order dependent. Lastly, repeated usage of the phrases “in one embodiment,” “an alternative embodiment,” or an “alternate embodiment” does not necessarily refer to the same embodiment, although it may.  
         [0013]    [0013]FIG. 1 illustrates a communication system according to one embodiment of the present invention. The system  100  includes a private server  110 , a client device  120  such as a user computer  120 , and a private side firewall  130  on a private side of a public network  160 . The system  100  further includes a public server  140  coupled to the public network  160 . The public server  140  may be directly coupled to the public network  160 , or, optionally, a firewall  150  may be placed between the public server  140  and the network  160 .  
         [0014]    [0014]FIG. 2 illustrates a communication system according to another embodiment of the present invention. The system  200  includes the private server  110  and the private side firewall  130  on a private side of the public network  160 . The system  200  further includes a client device  120 ′ such as a user computer  120 ′ and the public server  140  coupled to the public network  160 , with or without the intermediate firewall  150 .  
         [0015]    According to the embodiments shown in FIGS. 1 and 2, client device  120 ,  120 ′ and public server  140  communicate in accordance with HTTP, as do client device  120 ,  120 ′ and private server  110 . Private server  110  and public server  140  communicate using any protocol allowed by firewall  130 . Of course, it should be appreciated that the present invention encompasses protocols besides HTTP.  
         [0016]    The firewalls  130 ,  150  allow incoming HTTP connections, although whether an incoming HTTP connection from a particular source is allowed will depend on the trust of the firewall in the source. As a firewall for a public server  140 , the firewall  150  will generally allow incoming HTTP connections. As a firewall for a private server  110 , the firewall  130  may, for example, only accept HTTP connections from trusted sources. For both embodiments shown in FIGS. 1 and 2, the firewall  130  allows private server  110  to initiate communications with public server  140 , using a set of, for example, one or more prearranged Transmission Control Protocol (TCP) ports. The firewall  130 , however, does not allow public server  140  to initiate communications with private server  110 . According to the embodiment shown in FIG. 1, client device  120  is located behind the firewall  130  and thus has direct access to private server  110 . In the embodiment shown in FIG. 2, the client device  120 ′ is located outside of the private side firewall  130  and is authorized to communicate with the private server  110  because the firewall  130  permits client device  120 ′ access to, for example, TCP port  80  (HTTP) of the firewall  130 .  
         [0017]    According to both embodiments, client device  120 ,  120 ′ submits an HTTP request to public server  140  via public network  160  that causes public server  140  to generate results that the public server  140  is being directed to report to private server  110 . When public server  140  responds to the HTTP request of client device  120 ,  120 ′, public server  140  returns an HTTP redirect message that directs client device  120 ,  120 ′ to fetch a page, such as a World Wide Web page, from the private server  110 . Based on the redirect message, client device  120 ,  120 ′ generates an HTTP request and sends the HTTP request to private server  110 . Based on the HTTP request received from client device  120 ,  120 ′, private server  110  becomes aware that results are available at public server  140 . If there is no content associated with the HTTP request and the display on client device  120 ,  120 ′ is to remain unchanged, private server  110  responds immediately to client device  120 ,  120 ′ with an HTTP No Content response. Since private server  110  is on the private or trusted side of the firewall  130 , the private server  110  is permitted to initiate a connection with public server  140  to retrieve the results. The private server  110  preferably requests the information from the public server  140 . The request for information can be thought of as a poll to public server  140  that is virtually guaranteed to be successful because of the prior notification received from client device  120 ,  120 ′ that public server  140  has information to report. If private server  110  is to give client device  120 ,  120 ′ positive feedback that the results have been transferred, the private server  110  can send to client device  120 ,  120 ′ a suitable hypertext markup language page which may be based on the results.  
         [0018]    Thus, methods and apparatus for securely, efficiently, and timely communicating information between a public side device and a private side device are described. Although the present invention has been described with reference to specific exemplary embodiments such as those illustrated in FIGS. 1 and 2, it will be evident to one of ordinary skill in the art 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 rather than a restrictive sense.