Abstract:
A method and a computer program device for pushing data from at least one source entity to at least one client entity over a network, a client entity being characterized as having a particular operating state. The method and computer program device comprise the steps of: transferring data from the at least one source entity to a push proxy entity for subsequent transmission of the data to the client entity; requesting a notification regarding the particular state of the client entity; monitoring a state of the client entity until the client entity is in the particular operating state and sending a notification communicating the state to the push proxy entity; and transferring data to the client entity in response to receiving the notification. The state notification may specify push information, which may be used to determine a least expensive device to which to transfer given data. The state notification also reduces the network-polling load by initiating each poll.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention is related to data transmission in a computer network, and more particularly to a unique data push technology where data is transmitted to recipients according to a particular state of the intended recipients. 
     2. Description of Prior Art 
     The standard client-server information push model is not efficient for pervasive computing (PvC) entities, which for the most part are disconnected from the network. Servers uselessly attempting to push data to disconnected clients waste resources, such as the CPU, the RAM, and the network bandwidth in the process. 
     Push 
     In a standard push model, such as HTTP Push, a given push source server (PSS) sends out new information to all subscribed clients. This works well in networks where clients are actively connected to the network most of the time and the network has sufficient bandwidth for the transmission. Such clients are able to receive the transmissions. However, because PvC devices are mostly disconnected from the network, this model fails since the majority of the transmissions will fail. 
     Push source servers may attempt to avoid transmissions to disconnected clients by checking the availability of the target clients before each transmission. This approach still results in heavy network load due to the large number of status checking probes. 
     Pull 
     If any given client machine was forced to request all information sent to it, e.g., using the HTTP GET request, then every data transmission would be guaranteed to be sent to an available client. The problem with the pull scenario is that because there is no way for a given client to know when or if a given source server has any new information, the client is forced to make many unnecessary pull requests to ensure that any and all new information is retrieved. This will result in a heavy network load due to the large number of unnecessary pull requests. 
     Poll 
     Yet another approach, similar to the pull technique, is polling, like that used by the PointCast Network http://www.pointcast.com, an Internet news service broadcasting personalized news and information directly to clients&#39; computer screens. In polling, just as with the pull approach, additional network load is created by clients having to continually request information from source servers, even when no new information is in fact available, to ensure that any and all new data is retrieved. 
     Since PvC entities are already bandwidth-challenged, there remains a need for a way to enable an automated delivery of information, especially for that which is critical, yet only infrequently provided, such as bug fixes or virus checker updates. 
     SUMMARY OF THE INVENTION 
     In accordance with the aforementioned needs, the present invention is directed to a method and an apparatus for enabling a network server to trigger the transfer of data from a source server to a client entity, especially such that is often disconnected, like a PvC device, based on the client entity&#39;s particular state, like a connection to the network, for instance. The network server, which will be referred to as an “awareness server,” provides access to the transient status information of the network client entities, such as users, devices, applications, etc. The status information specifies whether a given device is connected to the network, a given user is logged, and whether a given user is actively participating in a given application. The process by which the awareness server triggers data transfers comprises the following steps: 
     the source server requesting the awareness server to notify it when a specific 
     client entity is in a particular state; 
     the client entity being in or entering the particular state; 
     the awareness server sending a notification to the requesting server after learning 
     of the specific client entity&#39;s state; and 
     the source server receiving the notification and transferring data to the specific 
     client entity. 
     The awareness server may also initiate data transfers from an intermediate proxy server in which push requests from source servers to target client entities are queued. Other methods are also provided to enable awareness notifications to be generated based on different criteria including: 
     whether a given client entity is connected and the manner of the connection, for example, the target client entity becomes TCP/IP linked at speeds of 14.4 Kbps or faster; 
     whether a given client entity is executing a particular application, for example, a web browser, and the manner of the execution; 
     whether a connection to a given client entity is secured and the manner of the connection, for example, when the target client entity becomes linked using SSL; 
     whether or not a given user is currently connected to the network, returning the network address of the user&#39;s current device in the notification; and 
     who is using a given client entity, for example, when the target client entity is being used by a particular user. 
     Methods are further provided for the awareness server to obtain state information by: 
     actively monitoring requested state and state changes; 
     learning of states or state changes from the target client entities themselves; and 
     learning of states or state changes from other servers, for example, learning from an Internet Access Provider when a given client is connected to the network. 
     Additional methods are provided for: 
     specifying information required for pushes in the awareness notifications, e.g., the port number of the application to which to transmit a given push; 
     determining the least expensive client device to which to transfer the given data, by using the awareness server; and 
     reducing the load of polling on the network, such as that done by network SNMP-based management servers, by initiating each poll by an awareness notification. 
    
    
     BRIEF DESCRIPTION OF DRAWINGS 
     The foregoing objects and advantages of the present invention may be more readily understood by one skilled in the art with reference being had to the following detailed description of a preferred embodiment thereof, taken in conjunction with the accompanying drawings wherein like elements are designated by identical reference numerals throughout the several views, and in which: 
     FIG. 1 is a diagram of a network having features of the present invention including a standalone push proxy; 
     FIG. 2 is a component diagram of an awareness server; 
     FIG. 3 is a flow diagram of the awareness server logic including the awareness request handler; 
     FIG. 4 is a flow diagram of the awareness notification handler; 
     FIG. 5 is a component diagram of a push proxy; 
     FIG. 6 is a flow diagram of the push proxy logic including the proxied push request handler and the proxied push handler; and 
     FIG. 7 is a diagram of a network having features of the present invention including server-side push proxies. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     In the preferred embodiment, the present invention is directed to a method and apparatus for providing HTTP PUSH transmissions. Those skilled in the art will understand that other types of transmissions, including but not limited to e-mail and multimedia broadcast may be handled similarly. 
     FIG. 1 shows a diagram of an overall logical network topology. PSS  1020 ,  1030 , an awareness server  1010 , and a push proxy server  1040  are directly connected to the network  1000 . Some examples of the network  1000  include, but are not limited to, the Internet, the World Wide Web, an Intranet and local area networks (LANs). 
     The client devices  1050 ,  1060  are locally connected to the push proxy server  1040 . All communication between the clients  1050 ,  1060  and the network  1000 , passes through the push proxy server  1040 . Although only two PSS  1020 ,  1030  are depicted, it is understood that the present invention is applicable to any number of such servers. Similarly, the present invention is applicable to any number of clients. 
     The PSS  1020 ,  1030  are essentially standard HTTP servers including, but not limited to IBM&#39;s Internet Connection Server (ICS) . The only unique feature of the PSS  1020 ,  1030  is that they route all pushes through a particular push proxy server  1040 . This feature may be added to an ICS-based server using ICS&#39; API (ICSAPI), which enables the development and inclusion of modules that customize the behavior of the ICS server. An ICS server may be configured to hand off control to such a module at a particular point during the processing of requests. The module may perform its task and then either return control to the server to complete the transmission, or complete the transmission itself and notify the server when it is done. 
     In the case of the PSS  1020 ,  1030  the added module takes control before the data is finally pushed to the subscribed client  1050 ,  1060  and, rather than sending the data to the client  1050 ,  1060 , connects to the push proxy  1040  and specifies where the data should be sent. This proxy routing is part of the HTTP standard specified in HTTPD RFC. The awareness server  1010 , the PSS  1020 ,  1030  and the push proxy server  1040  may be implemented on any computing nodes including, but not limited to products, such as IBM S/390 SYSPLEX, SP2, or RS6000 workstations. 
     The clients  1050 ,  1060  may include an IBM WorkPad, a PC, various workstations, set top box, etc. The software running on the clients  1050 ,  1060  may include, but is not limited to, the Netscape&#39;s Navigator web browser. 
     The awareness server  1010  provides notification of when the specified clients or targets have reached a desired state, for example, connected to the network. As shown in FIG. 2 the awareness server  1010  (FIG. 1) includes a CPU  3000 , a memory  3020 , such as RAM, and a storage device  3010 , such as a disk or other direct access storage device (DASD). 
     The awareness server  1010  (FIG. 1) logic preferably embodied as executable computer code, is loaded in to the memory  3020 , either remotely over the network or locally from an optical CD-ROM, magnetic storage, such as disk, or DASD  3010 , for execution by CPU  3000 . The executable computer code loaded into memory  3020  preferably includes an awareness request handler  3030  to accept and to service a clients&#39; requests, an awareness notification handler  3040  to notify clients of the status of their requests, and a request buffer  3050  to store current requests. 
     As shown in FIG. 3 the awareness server  1010  (FIG. 1) waits for input in step  4000 , possible inputs including requests for status notification received from the network. After the input is received, step  4010  determines whether the input is an awareness request, i.e., a request to notify that a specified client has reached a particular state. If the request is not a request for status notification, then a miscellaneous handler is invoked in step  4030 . Following the execution of the miscellaneous handler in step  4030 , the program control returns to step  4000  to wait for further input. 
     However, if the input is an awareness notification request, then the awareness request handler  4020  is invoked. At step  5010  the request handler reads the requestor&#39;s and the target client&#39;s IDs from the request, e.g., the hostname of the server asking to be notified and the hostname of the client device whose status is being announced. At step  5020 , the awareness request handler  4020  adds a new entry to the request buffer  3050  (FIG. 2) indicating the extracted IDs of the requester and of the target client. Following the execution of the awareness request handler  4020 , the program control returns to step  4000  to wait for further input. 
     FIG. 4 shows the processing of the awareness notification handler  3040  (FIG. 2) which is continually running as a background process in the CPU  3000  (FIG. 2) of the awareness server  1010  (FIG.  2 ). 
     A local pointer is moved to the first entry in the request buffer  3050  (FIG. 2) in step  6000 . The requestor&#39;s and the target client&#39;s IDs are read from the pointed to entry in step  6010 . In step  6020  the status of the target client is checked. 
     The status may be the connectivity status and may be checked by such programs as PING, or from a notification received from the target client device, i.e., whenever a given client device connects. Ascertaining the status of a given target client actively connected or participating in a particular application may be accomplished by requesting the target client&#39;s status from the application server. The awareness server  1010  (FIG. 1) itself may request to be notified by outside servers. For example, it could learn when a given target client connects by asking the target client&#39;s Internet access provider for a notification when the given client connects. If a notification is received, then the target client is connected, otherwise the client is still disconnected. 
     In step  6030  a determination is made whether the target client has reached a desired status. If the target client has reached the desired status, then in step  6040  a notification is sent to the requester using TCP, UDP or any other network transport protocol or higher level applications like e-mail. The current entry is then deleted from the request buffer  3050  (FIG. 2) in step  6050 . If however, the target client has not reached the needed status, then steps  6040  and  6050  are skipped. 
     In step  6060  if it is determined that there are no more requests in the request buffer  3050  (FIG.  2 ), then processing continues at step  6000 . If there are further requests in the request buffer  3050  (FIG.  2 ), then in step  6070 , the local pointer is advances to the next entry, and the processing continues in step  6010 . 
     The awareness server  1010  (FIG. 1) may send notifications for any number of reasons, some of these reasons may include: 
     whether a given client entity is connected or the manner of the connection, for example, the target client entity becomes TCP/IP linked at 14.4 Kbps or faster; 
     whether a given client entity is running a particular application, e.g., when the target client entity is running a web browser, or the manner of the execution of the application. 
     whether a connection to a given client entity is secured and the manner of the connection, for example, a client entity becomes linked using SSL. 
     who is using a given client entity, for example, a particular user is the client. 
     The awareness server  1010  (FIG. 1) may also return critical information in the notifications, such as the port number on which the target client entity&#39;s push recipient application, such as a web browser, is running. This critical information may be read and used by the push proxy server  1040  (FIG. 1) when the notification is received. 
     The push proxy server  1040  (FIG. 1) shown in FIG. 5, queues up push requests and executes the final transmission to the target client device after being notified by the awareness server that the given client device is able to receive the transmission. The push proxy server  1040  (FIG. 1) includes a CPU  10000 , a memory  10020 , such as RAM, and a storage device  10010 , such as a disk or a DASD. 
     According to the present invention, the push proxy logic embodied as executable computer code, may be loaded remotely over the network or locally from an optical CD-ROM or magnetic storage, such as disk, or DASD  10010  into memory  10020  for execution by the CPU  10000 . The computer code loaded into the memory  10020  includes a proxied push request handler  10030 ; a proxied push handler  10040 ; and a proxied push database  10050  including but not limited to IBM&#39;s DB 2  Database Product. 
     FIG. 6 illustrates the push proxy program flow. As shown in FIG. 6, the push proxy waits from input in step  11000 . When the input is received, a determination is made in step  11010  whether the input is a PUSH request. If it is a PUSH request, then, the proxied push request handler  11020  is invoked. Otherwise, processing continues in step  11030  where it is determined whether the input is an awareness notification. If the input is an awareness notification, then the proxied push handler  11040  is invoked. Otherwise, if the input is not an awareness notification the appropriate miscellaneous handler is invoked after which the processing continues in step  11000 . 
     The proxied push request handler  11020  queues up the push feeds from the PSS  1020 ,  1030  (FIG.  1 ). The data and the target client&#39;s ID, such as the client&#39;s hostname or the IP address, are read from the request in step  12000 . If it is determined in step  12010 , that a given ID does not already have an entry in the proxied push database  10050  (FIG.  5 ), then an entry is created in step  12020 . 
     In step  12030 , new data is added to the queued data for the read ID. A notification request is sent to the awareness server  1010  (FIG.  1 ), in step  12040 , specifying the ID for itself and the target client, after which the processing continues in step  11000 . 
     As mentioned, after receiving a notification from the awareness server  1010  (FIG. 1) for a specific client device, the proxied push handler  11040  pushes the queued data to that specific client device. 
     Particularly, at step  13000 , the proxied push handler reads the client&#39;s ID from the notification, and retrieves of the data queued for the given ID from the proxied push database  10050  (FIG. 5) at step  13010 . Then, at step  13020 , this data is pushed to the target client. In step  13030 , the proxied push database entry for the given ID is deleted and the processing continues in step  11000 . 
     Sending queued pushes only after being notified that the target client is connected to the network and is listening, eliminates many needless transmission attempts which would have been executed in the absence of this knowledge. This aspect of the present invention may also be used to optimize polling applications, for example, the status polling performed by SNMP-based network management applications. If status requests are only sent when the target network devices are connected, as indicated by notifications from an awareness server, then resource-wasting requests to disconnected devices are eliminated. 
     As shown in FIG. 7, the push proxy server  1040  (FIG. 1) need not be a standalone machine. Instead of having the push proxy run remotely, each PSS  2020 ,  2030  may have its own server-side proxy running concurrently in parallel with the PSS system. In this configuration, a given PSS would use its own hostname or IP address as that of the push proxy. 
     Multiple push proxies may be used to spread out processing and network load. With multiple push proxies, each PSS would have a choice of which one to use. Another way to spread out processing and network load is to employ multiple awareness servers, so that a push proxy may request notification from more than one awareness server. 
     The target client&#39;s ID sent to the awareness server  2010  could be a user ID, such as a name like “Luanda Chen”, rather than a device ID, such as a network address like 192.62.1.1. Given a user ID, the awareness server could notify a push proxy when a particular user is connected, specifying the address of the user&#39;s current device in the notification. 
     The awareness server notifications may also be used to route transmissions as inexpensively as possible, for instance, in response to an awareness notification request for a particular user, the awareness server  2010  may determine all the currently available user devices, then determine the least expensive device to which to send data, and finally reply to the notification request with a notification which specifies the address of this device. 
     While the invention has been particularly shown and described with respect to illustrative and preferred embodiments thereof, it will be understood by those skilled in the art that the foregoing and other changes in form and details may be made therein without departing from the spirit and scope of the invention that should be limited only by the scope of the appended claims.