Abstract:
A system for enabling server alerted synchronization between a client device and a synchronization server where the network address of the client device is subject to arbitrary reassignment by the network operator without communication with the synchronization server. The client device actively responds to dynamic assignments of a network address to the client device by a network operator by establishing a network connection with and transmitting the network address to a synchronization server operated independent of the network operator. The identification of the synchronization server is determined from configuration data maintained by the client device. The client device then provides for the establishment of a network connection with the synchronization server to support immediate receipt of server alerted synchronization notification messages.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     The present invention is generally related to dynamic network systems and, in particular, to a system and methods of enabling server alerted synchronization and related data synchronization schemes to operate subject to arbitrary dynamic network addressing changes.  
         [0003]     2. Description of the Related Art  
         [0004]     The deployment and use of mobile, characteristically wireless, client devices is widespread, growing, and likely to continue to grow at an accelerating pace. Even while the fundamental nature and capabilities of the client devices continue to evolve, substantial investments are being made by network operators to define, install and operate extended wide area communications networks. Given the varied technological, commercial and even geographical interests involved, the network operators and related service providers must contend with a large number of different, and often conflicting, interoperability standards in determining how best to implement specific networks and provide corresponding services. In almost all instances, universal interoperability between different networks, including among the various client and base devices designed for and serviced by the different networks, is precluded. Instead, actual interoperability is achieved functionally through conformance with selected, well-defined standards typically as developed by industry oriented and supported associations.  
         [0005]     The Open Mobile Alliance (OMA; www.openmobilealliance.org) is responsible for creating a number of interrelated technology standards intended to facilitate broad, if not global user adoption of mobile data services by specifying market driven mobile service enablers that ensure service interoperability across devices, geographies, service providers, operators, and networks, while allowing businesses to compete through innovation and differentiation. An example is the OMA SyncML Device Management and Data Sync standards described in the current standard proposal documents OMA-TS-DM-Protocol-V1 — 2-20050826-C and OMA-SyncML-DataSyncProtocol-V1 — 2-200400601-C. While popularized as the SyncML Protocol, the standards are more formally referred to as implementing the OMA DM and DS protocols. The OMA DM (device management) protocol provides the core mechanisms for over-the-air (OTA) provisioning and configuring of mobile devices, while the OMA DS (data synchronization) protocol describes the basic transactions required for device data synchronization.  
         [0006]     Mobile devices are evolving from simple user interface systems to computing platforms capable of supporting a diversity of application programs. The distributed and variably disconnected nature of mobile devices, however, typically requires applications to support a combination of local and remote application specific data storage. These applications must further support synchronization of the client local application data, subject to potential disconnected modification, with remote stored data, typically through a network connected data server. The OMA DS protocol describes a standards-based protocol intended to enable client applications resident on mobile devices to interact and synchronize application data with remote server data systems. The desired user experience is, of course, that any required data synchronization occur transparently and without apparent delay.  
         [0007]     The OMA DS protocol proposes a coordinated transport system for messages and responses to establish a transaction session for data synchronization between a mobile device and a synchronization server, typically referred to as a SyncML server. The transport medium is not specified, allowing for different implementations to accommodate different network systems and service offerings. The data difference resolution algorithms used to identify the data exchanges necessary to effect synchronization are also not specified. Different application and service providers are therefore able to implement synchronization algorithms that are the most appropriate for the particular services and applications they support.  
         [0008]     The OMA DS protocol implicitly supports both client initiated and server initiated synchronization transactions. For simplicity, application data synchronization is driven by the client application. Server initiated synchronization is achieved by forwarding a synchronization request message from the server to the client to prompt the client application to perform synchronization. A particular limitation of the OMA DS protocol is that the specification does not define the detailed protocol for communicating server alerted synchronization messages to the mobile devices. Rather, the specification specifies that the synchronization server must be able to address messages to particular mobile devices as necessary to perform server alerted synchronization. The specification further defines the form and content of the server alerted synchronization message that must be sent by a SyncML server to trigger a specifically identified mobile device into performing a synchronization transaction. Server alerted synchronization is, of course, highly desired to minimize any apparent delay in presenting updated application specific data to a mobile device user and maintaining the integrity of the information available to other users of the SyncML server.  
         [0009]     Conventionally, a network address, most typically an Internet Protocol (IP) address, is used to identify a mobile device in synchronization transactions. For mobile devices capable of being assigned a network address, which includes essentially all current mobile devices capable of data synchronization, a network address is dynamically assigned whenever the mobile device connects to the network. The network address is also dynamically reassigned, with no guarantee of consistency in the value of the IP address provided, whenever the mobile device reconnects with the network, however a particular network operator may define a reconnection. The network operator may also reassign the network address based on criteria exclusively in the control and discretion of the network operator. A mobile device therefore must be capable of operating under the assumption that the assigned network address will be changed arbitrarily without prior notice.  
         [0010]     Since there is no specification defined way of providing a synchronization server with the network address of a mobile device, either within or in anticipation of a synchronization transaction, service providers and network operators have resorted to a number of alternative methods. One such method requires proprietary integration of the synchronization servers with the network support servers that provide the network addresses. To illustrate, US Patent Publication 2001/0028636 describes a wireless application protocol (WAP) gateway system that manages the assignment of IP addresses to mobile devices on connection with the attached wireless network. The IP address assigned to a mobile device is recorded against the unique MSISDN identifier of a device in a database available only to servers implemented internal to the gateway system. While IP addresses are generated in a conventional manner, the assignment of IP addresses to mobile devices operating within the network operator network is performed using low-level, typically proprietary protocols. These IP addresses, as assigned, are recorded in a database embedded within the network operator server system.  
         [0011]     For a number of reasons, most involving the desire to maintain a commercial advantage over the services provided to or accessible from the mobile devices and security concerns, the IP database internally maintained by the network operator is not publically accessible. Furthermore, network operator systems provide no public notice of IP address assignments, including reassignments, to the network operator managed mobile devices or other third party systems. Without the ability to reliably contact and interact on demand with the mobile devices, which is dependent on a reliable knowledge of the network address of the mobile devices, third party synchronization servers are unable to provide commercially acceptable services. Consequently, only network servers implemented as an integral part of the network operator server systems are able to support data synchronization services. A further undesirable result is that client application data synchronization is limited to only those applications actually supported by the particular network operator and at a cost structure relatively unconstrained by direct competition.  
         [0012]     An alternative approach frequently used to support conventional client applications requires the use WAP-push messaging to transfer synchronization notification messages. The use of WAP-push transport from a SyncML server to a mobile device to trigger a synchronization transaction is conformant with the OMA DS protocol specification. Due to the limited data capacity of short message service (SMS) packets, multiple SMS messages must typically be sent to convey a synchronization notification message. The mobile device then responds by creating the network connection with the SyncML server as necessary to conduct the synchronization transaction. The fundamental drawback of this approach is that the SMS messages must route through the network operator WAP gateway. Such messaging services are not free of direct monetary costs. Given the desired frequency of data synchronizations, even nominal use of client applications using server alerted synchronization becomes undesirably expensive.  
         [0013]     The need for server alerted synchronization can be avoided, in limited circumstances, by having the mobile device either continuously maintain an active connection to the synchronization servers or periodically poll the servers for updates. Maintaining an active connection has the specific benefit of avoiding any noticeable delay in retrieving application data updates. Any reassignment of the network address will, however, result in the loss of the network connection. Therefore, these systems typically require integration with the network operator system. In any event, the cost, in terms of battery life and server resources, makes maintaining an active connection undesirable.  
         [0014]     Having the mobile device poll the server at defined intervals reduces battery drain, as compared to maintaining a continuous connection, but can result in an significantly increased data synchronization latency. If the polling interval is reduced to compensate, then battery life is again compromised and the synchronization servers are required to support a significantly increased load due to the increased rate of network connection setup and tear-down.  
         [0015]     Other transport systems for providing synchronization notification messages to mobile devices and of updating synchronization servers are not generally well known. Such systems are typically based on proprietary protocols and integration of server systems within a single provider network. Consequently, there is a need for an open system that allows client devices to update network addresses to synchronization servers interoperably within and across networks independent of the network operator and dedicated system providers.  
       SUMMARY OF THE INVENTION  
       [0016]     Thus, a general purpose of the present invention is to enable the reliable transfer of mobile device network addresses to synchronization servers to support data synchronization interoperably over networks supported by and operationally independent of any network operator.  
         [0017]     This is achieved in the present invention by providing a system and methods of enabling server alerted synchronization between a client device and a synchronization server where the network address of the client device is subject to reassignment arbitrarily by the network operator without communication between the network operator and the synchronization server. The client device actively responds to such dynamic network address assignments by establishing a new network connection with and transmitting the network address to the synchronization server independent of the network operator. The identification of the synchronization server is determined from configuration data maintained by the client device. The client device then provides for the establishment of a network connection with the synchronization server to support receipt of server alerted synchronization notification messages.  
         [0018]     An advantage of the present invention is that the client device operates to actively enable synchronization server support for the delivery of server alerted synchronization notification messages to the client device. Preestablished internal configuration data is used to identify a set of one or more synchronization servers that can provide data synchronization services for the client applications executed on the client device and, further, may originate server alerted synchronization notifications.  
         [0019]     Another advantage of the present invention is that interoperation between client devices and synchronization servers on behalf of application servers occurs without dependency on or coordination with any network operator system. The ability of the client applications to reliably exchange synchronization data is not compromised by the arbitrary assignment and reassignment of the client device network address by a network operator. In addition, by being independent of any network operator, the present invention enables open cost and feature competition between synchronization service providers.  
         [0020]     A further advantage of the present invention is that multiple synchronization servers can be leveraged to support data synchronization with individual client devices, thereby ensuring data synchronization transaction availability through synchronization system redundancy and enabling efficient, scaleable, and cost effective use of the synchronization servers. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0021]      FIG. 1  is a simplified network diagram illustrating the operating environment of the preferred embodiments of the present invention;  
         [0022]      FIG. 2  provides a block diagram of the preferred implementation of the client hardware and software systems used in a preferred embodiment of the present invention;  
         [0023]      FIG. 3  is a message sequence diagram illustrating a data synchronization transaction including propagation of a synchronization notification message as performed by a preferred embodiment of the present invention;  
         [0024]      FIG. 4  is a message sequence diagram illustrating a synchronization server update transaction as performed by a preferred embodiment of the present invention;  
         [0025]      FIG. 5  is a state diagram illustrating a preferred implementation of a device inventory update operation performed by a synchronization server in a preferred embodiment of the present invention;  
         [0026]      FIG. 6  is a block diagram describing functional operation of a client device implementing a preferred embodiment of the present invention;  
         [0027]      FIG. 7  is a block diagram describing functional operation of a synchronization server system implementing a preferred embodiment of the present invention; and  
         [0028]      FIG. 8  is a flow diagram illustrating the interoperation of a client device and synchronization server in accordance with a preferred embodiment of the present invention. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0029]     A preferred operating environment  10  of the present invention is shown in  FIG. 1 . As will become clear from the following detailed description of the invention, wherein like reference numerals are used to designate like parts depicted in one or more of the figures, the present invention enhances the ability of service providers to deliver data synchronization services to client devices  12  operationally independent of network operators. In the preferred embodiments, the client devices  12  are typically mobile wireless devices, including cellular telephones  14  and various keyed  16  and pen-based  18  personal information management type computer systems. Communications with the client devices  12  is provided by a wireless network  20 , typically cellular in architecture, that is managed and maintained by a network operator, here generally represented by a network operator system  22 . Generalized network communications, typically Internet-based, are routed through the network operator system  22  and Internet  24 .  
         [0030]     A server system  26  is established to provide network based data synchronization services to subscribing mobile devices  12 . The server system  26  operates independent of the network operator system  22 . For purposes of the present invention, the server system  26  is operationally independent of the network operator system  20  where no network operator specific services are required from the network operator system  20  in order to establish and conduct network communications between the mobile devices  12  and the server system  26 . The only essential service of the network operator system  20  is to transport IP data streams between the mobile devices  12  and the server system  26 .  
         [0031]     In the preferred embodiments of the present invention, the server system  26  implements the SyncML server alerted synchronization protocol, conformant with a current OMA DS Protocol Specification, to enable data synchronization between client application programs as executed on the client devices  12  and one or more application servers  28 . Each application server  28  hosts, directly or indirectly, a distributed user application and the centralized user data storage. Typical distributed user applications include conventional mobile email and calendaring applications. Alternately, or in addition, an application server  30  may directly implement the SyncML server alerted synchronization protocol and thereby also operate as a SyncML server for the distributed user applications hosted by the application server  30 . Preferably, the SyncML  26 ,  30  and application servers  28  are also operationally independent of the network operator system  20 .  
         [0032]     A preferred architectural implementation  40  of a client device  12  suitable for use with the present invention is shown in  FIG. 2 . The hardware platform includes a conventional embedded processor control system  42  supporting display  44  and input device  46  interfaces. A conventional radio transceiver  48  enables communications with the applicable wireless network  20 . Conventional non-volatile  50  and standard  52  random access memories provide local storage for an embedded operating system  54  and one or more distributed user client application programs  56 . While the embedded operating system  54  is typically proprietary, in relevant implementations a basic, standards compliant TCP/IP stack  58  is included to support conventional IP network communications. For the preferred embodiments of the present invention, the TCP/IP stack  58  implementation supports operation as a network server for inbound IP connections. While new client device  12  implementations are increasingly incorporating server-capable TCP/IP stacks  58 , the present invention also detects and supports use of client devices  12  capable of client-only TCP/IP operation.  
         [0033]     A WAP client layer  60  is typically present to support low-level configuration and control of the client device  12 . The network operator server system  22  is typically implemented as a WAP gateway to provide the services required for conventional subscriber identification of the client device  12  and, relevant to the present invention, assign an IP address to the client device  12 . The assignment of the IP address is, in effect, performed arbitrarily by the network operator server  22 , both in terms of the specific IP address value and the timing of assignments. Conventionally, an IP address will be assigned by the network operator server  22  to a client device  12  each time the client device  12  connects to the wireless network  20 . Additionally, the network operator is free to assign a new network IP to the client device  12  at any time. While reassignments typically occur in response to movements by the client device  12  within the network topology of the wireless network  20 , as may be forced by practical network implementation constraints, network address reassignments are ultimately determined based on criteria determined by the network operator. Conventionally, client devices  12  are required to immediately accept and use the network operator assigned IP address.  
         [0034]     A SyncML controller layer  62  is provided in accordance with the present invention to implement and manage initialization for the SyncML server alerted synchronization protocol. In accordance with the present invention, the SyncML controller layer  62  further interoperates with the TCP/IP stack  58  to monitor assignments and reassignments of the network IP and autonomously update the SyncML servers  26 ,  30  operationally independent of the network operator server system  22 . The network identity of the SyncML servers  26 ,  30  may be specified as fixed values coded into the SyncML controller layer  62  or included as configuration data  64  associated either with the SyncML controller layer  62  or applications  56 . Where stored as fixed values, conventional network routing and load-balancing techniques may be used to manage the operation of the identified SyncML servers  26 ,  30 . By alternately storing the identity of the SyncML servers  26 ,  30  as configuration specific data  64 , different specifically identified SyncML servers  26 ,  30  can be discretely assigned as desired to particular client devices  12  and individual client applications  56 .  
         [0035]     The initialization function of the present invention is shown in  FIG. 3  the context of a server alerted synchronization transaction  70 . An initialization phase  72  is required to identify a client device  12  to a SyncML server  26 ,  30  to enable a client application  56  present on the client device  12  to exchange synchronization data with a corresponding application server  28 . For the preferred embodiments of the present invention, the initialization phase  72  is responsible for transferring the current assigned network IP address and a unique device identifier, such as the MSISDN of the client device  12 , to the SyncML server  26 ,  30 . Where non-IP based network protocols are used, the assigned network protocol device identifier is provided. Also, rather than providing a device specific identifier, a set of one or more client application unique identifiers can provided in correspondence with the network address. In each case, the SyncML server  26 ,  30  is provided with initialization information sufficient to establish communications with a specific client device  12 .  
         [0036]     In accordance with the SyncML server alerted synchronization protocol, synchronization order messages  76  are provided by an application server  28  to a SyncML server  26 . An equivalent message is passed internal to the SyncML and application server  30 . A synchronization order message  76  is generated with respect to a client application  56  whenever the application server  28  receives or develops data appropriate for synchronization with a corresponding client application  56 . The synchronization order messages  76  preferably includes a synchronization identifier, such as an MSISDN, that can be uniquely associated with the desired client device  12  by the SyncML server  26 ,  30 . A synchronization notification message  78 , also referred to as a server synchronization package # 0 , is then forwarded to the client device  12 . In response, the client device  12  initiates a synchronization transaction  80 . Typically, within the synchronization transaction  80 , each client application  56  is polled internal to the client device  12  to perform an application specific data synchronization check and update operation. After the client applications  56  have completed synchronization  82 , a final synchronization result message  84  is returned to the initiating application server  28 .  
         [0037]     Viewed as a sequence of message transactions  90  as shown in  FIG. 4 , the initialization and, as necessary, reinitialization of client server communications  72  is initiated in response to the assignment of a network address  92  by the network operator server  22 . In response, the SyncML controller layer  62  transmits messages  94  to the SyncML servers  26 ,  30  identified from the local configuration data  62 . Depending on the networking capabilities of the client device  12 , communications channels are established  96  with the SyncML servers  26 ,  30  to allow the client device  12  to receive subsequent synchronization notification messages  78  as originated by the SyncML servers  26 ,  30 .  
         [0038]     The preferred operation  110  of a SyncML server  26 ,  30  in response to an update message  112  from a client device  12  is shown in  FIG. 5 . Preferably, a SyncML server  26 ,  30  implements a network connection listener  114  at a network address, such as “http://sync4j.com/syncml”, well known to client devices  12 . Alternately, the applicable SyncML server  26 ,  30  network address is provided to and stored as configuration data  64  upon subscription by the client device  12  to the SyncML services available through the corresponding SyncML server  26 ,  30 . Upon receiving an update message  112 , the SyncML server  26 , preferably performs an authentication transaction with a security manager  118 . For the preferred embodiments of the present invention, the update message  112  is a standard OMA DS protocol client alert message presenting a custom alert code. Authentication can then be performed by a basic-type authentication call  116  on the local OMA DS protocol defined security manager  118 . Alternately, degrees of greater security and authentication control may be added by, for example, requiring a secure socket layer (SSL) connection to the connection listener  114  and providing for LDAP or active directory-based authentication of the security credentials provided in the client alert message.  
         [0039]     Provided that the update message  112  is properly authenticated  120 , an update transaction  122  is then performed to add or update the client device  12  in an inventory database  124  preferably maintained by the SyncML server  26 ,  30 . The inventory database  124  preferably stores, at a minimum, the current network IP address correlated against the unique identifier of client device  12 . Preferably, the current network IP address is provided by the client device  12  as part of the update message. This is the current assigned IP address of the client device  12 . Additionally, an apparent network IP address is determinable from the network connection with the SyncML listener  114 . This apparent network IP address can used to identify the potential presence of a firewall, gateway, router or other proxy device in the network path. The assigned and apparent IP addresses are preferably recorded in the inventory database  124  for use, as appropriate, by the SyncML server  26 ,  30  in subsequently establishing and accepting connections with the client device  12 .  
         [0040]     The client device identifier is also included in the client alert message and is preferably checked against a local inventory list of the client devices permitted access to the SyncML server  26 ,  30 . This local serviceable client device list is preferably created and maintained through an administrative process in response to subscription by the client device  12  to the SyncML services available through the corresponding SyncML server  26 ,  30 . An update status response  126  is then returned to the client device  12 . For the preferred embodiments of the present invention, the status response  126  presents a status code to indicate success ( 200 ), use-polling ( 300 ), use-continuous-polling ( 301 ), unauthorized ( 401 ), device not found ( 404 ), or server error ( 500 ). The use-polling and use-continuous-polling status codes are invoked where the SyncML server  26 ,  30  recognizes from the IP address included in an update message that a client device  12  has been assigned an RFC 1918 private network or otherwise non-publicly accessible IP address. The use-polling status code requests the client device  12  to periodically establish a new network connection with the SyncML server  26 ,  30  to check for updates. The use-continuous-polling status code requests the client  12  to periodically establish a network connection that is maintained for a defined period, covering multiple update checks, thereby lessening the connection setup and tear-down load on the SyncML servers  26 ,  30 . In alternate embodiments, the response message may also return administrative information including an update of the network address to be used by a client device  12  in connecting with the network listener  114 .  
         [0041]     A preferred system architecture  130  detailing a preferred implementation of the SyncML controller layer  62  within a client device  12  is shown in  FIG. 6 . The SyncML controller layer  62  includes an address detection service  132  that monitors the address assigned to the client device. Depending on the existing capabilities of the embedded TCP/IP stack  58 , the address detection service  132  registers with the stack  58  to receive event-type notifications whenever a new network address is assigned. Alternately, the address detection service  132  periodically checks for changes in the current network address in use by the TCP/IP stack  58 . The specific behavior of the address detection service  132 , such as type and frequency of network address checks, may be controlled by configuration data  64 . Whenever use of a new network address is detected, an IP notification alert message is sent to the SyncML servers  26 ,  30 . The IP notification alert message is a standard OMA DS protocol alert message presenting the new network address and, optionally, the MSISDN of the client device  12 . A preferred form of the IP notification alert message is as follows:  
                                                   &lt;Alert&gt;              &lt;CmdID&gt;5&lt;/CmdID&gt;              &lt;Data&gt;745&lt;/Data&gt;              &lt;Item&gt;                 &lt;Source&gt;ip&lt;/Source&gt;                 &lt;Data&gt;80.125.0.120&lt;/Data&gt;              &lt;/Item&gt;              &lt;Item&gt;                 &lt;Source&gt;msisdn&lt;/Source&gt;                 &lt;Data&gt;+39111223344&lt;/Data&gt;              &lt;/Item&gt;           &lt;/Alert&gt;                      
 
         [0042]     The SyncML controller layer  62  also includes SyncML notification listener  134  and notification processor  136 . For the preferred embodiments of the present invention, the SyncML notification listener  134  is configured to listen for SyncML notification messages received through a direct TCP connection or, as a conventional alternative, through a WAP connection where the notification message is embedded in a standard series of WAP-Push messages. Each SyncML notification message is processed by notification processor  136  to initiate a synchronization transaction  80 . For the presently preferred embodiments, the notification processor  136  coordinates a data synchronizer  138  that provides a control interface to the client applications  56  through which the notification processor  136  can initiate the performance of an application specific data synchronization transaction for each client application  56 . Client data synchronization transactions are then performed by the client applications  56  using connections established through the WAP layer  60  or directly through the embedded TCP/IP stack  58  as determined by the client applications  56 . In alternate embodiments of the present invention, where multiple SyncML servers  26 ,  30  may be used, configuration data  64  may be checked by the notification processor  136  or individual client applications  56 , to identify the client applications  56  associated with the particular SyncML server  26 ,  30  that sourced a current SyncML notification message. Synchronization transactions are thereby initiated selectively for client applications  56  against only known SyncML servers  26 ,  30 .  
         [0043]     A preferred architecture  140  for SyncML servers  26 ,  30  is shown in  FIG. 7 . A client device update controller  142  preferably maintains a connection listener for IP notification alert messages. For the preferred embodiments of the present invention, the IP notification alert messages are provided through a TCP connection created on demand by a client device  12 . Each IP notification alert message is presented in the form of a single stateless HTTP POST request. Alternately, IP notification alert messages can be received through the WAP layer  60 . The client device update controller  142  is responsible for authenticating each received IP notification alert message and, where the IP notification alert message is authenticated, updating the client device inventory  144  maintained by the SyncML server  26 ,  30 . The structure of the device inventory  144  preferably includes an indexed association between unique client device  12  identifiers and the current network addresses of the client devices  12 . Additional information may be kept as desired for management of the inventory, including current connection status, and time of last connection, the type and status of the last synchronization operation, and the device capabilities of the client device  12  including, for example, the manufacturer, model and version of the client device  12 .  
         [0044]     Data synchronization transactions  80  are conducted by the client devices  12  and are, in general, client application specific. In general, a data synchronization transaction begins with a synchronization initiation request being forwarded by a client application  56  to a SyncML server  26 ,  30 . The synchronization request is parsed by the SyncML service controller  146  to determine the application server  28  identified by the request. The SyncML service controller  146  is responsible for establishing a network connection and forwarding the data synchronization request to the identified application server  28 . For the preferred embodiments of the present invention, the SyncML service controller  146  operates as a portal for synchronization transactions  80 . Where a client device  12  is capable of listening for network connections, an application server  28  may choose to independently establish a network connection to the client device  12  for performance of the data synchronization transaction  80  specific to the client application  56  as serviced by the particular application server  28 .  
         [0045]     In an alternate embodiment of the present invention, a connection monitor service  148  may be periodically executed by the SyncML server  26 ,  30  to maintain the client device inventory  144 . In particular, where an open connection is maintained by the SyncML server  26 ,  30  with client devices  12 , the network connection may not be closed when the client device  12  is inactivated or otherwise becomes unavailable. The connection monitor service  148  operates to periodically check current connections with the client devices  12  where identified from the client device inventory  144  as being active. Network connections are closed and corresponding server resources released for unreachable client devices  12 . The client device inventory  144  is correspondingly updated.  
         [0046]     The client communications initialization process  160  implemented by the preferred embodiments of the present invention is shown in  FIG. 8 . On a client device  12 , the address detection service  132  monitors  162  for any apparent change in the assigned network address. Detection is premised on timer events or on explicit network address change events generated by the embedded TCP/IP stack  58 . In both cases, the address detection service operates to periodically compare  164  the current network address with an internally maintained copy of the last assigned network address. Comparison is necessary in the case of timer events and preferred in the case of stack  58  generated events to screen for events that do not reflect an actual network address value change.  
         [0047]     When a change in the network address is detected, any outstanding network connections are dropped  166 . Any active data synchronization transactions will have already stopped due to the change in network address. The address detection service  132  then generates 168 an IP alert notification message for each of the SyncML servers  26 ,  30  known to the client device  12 . A network connection to each of the known SyncML servers  26 ,  30  is then created and the respective IP alert notification messages are sent  170 . If a network connection cannot be established, the address detection service  132  will periodically retry creation of the network connection. Where a connection is established but no acknowledgment of an IP alert notification message is received by the address detection service  132 , the IP alert notification message is periodically regenerated and resent.  
         [0048]     On a SyncML server  26 ,  30 , when an IP alert notification message is received  172  by the update controller  142 , the message is validated. Where valid, the client device inventory  144  is updated and an appropriate acknowledgment message is returned  174  to the client device  12 .  
         [0049]     Once the address detection service  132  on a client device  12  has received acknowledgment that a SyncML server  26 ,  30  has accepted an IP address update, the capabilities of the embedded TCP/IP network stack  58  are evaluated  176  to determine network connection management. Where the embedded TCP/IP network stack  58  lacks server capabilities or where the client device  12  assigned IP address is private, the network connection to the SyncML server  26 ,  30  is managed  178  by the client device  12 . Client management modes of managing the network connection include maintaining the existing network connection for use in subsequently receiving server alerted synchronization messages from the SyncML server  26 ,  30  by the client device  12 , periodically polling the SyncML servers  26 ,  30  potentially dependent on time-schedules determined from the configuration data  64 , or using a continuous-polling technique where a client initiated network connection is maintained for a defined period of time determined from the configuration data  64 , dropped, and then re-established after another period of time. If the embedded TCP/IP network stack  58  is capable of acting as a network server and a public IP has been assigned, the current network connection with the SyncML server  26 ,  30  is dropped  180 . A connection listener  182  is then launched  182  to receive connection requests from the SyncML server  26 ,  30  whenever a SyncML server  26 ,  30  is requested to send a server alerted synchronization message to the client device  12 .  
         [0050]     Thus, a system and methods of providing for the establishment of reliable network communications between a client device and SyncML server independent of the network operator system while allowing for arbitrary network address changes imposed by the network operator has been described. While the present invention has been described particularly with reference to the presently defined OMA DS protocol, the present invention will be applicable to subsequent revisions and additions to the OMA DS protocol and related protocols used to support data synchronization with mobile communications devices. Additionally, the client devices need not be mobile or wireless. The present invention is also applicable to computer systems where distributed clients, both wired and wireless, are subject to effectively arbitrary assignment of network addresses, including those that may freely transition between wired and wireless networks.  
         [0051]     In view of the above description of the preferred embodiments of the present invention, many modifications and variations of the disclosed embodiments will be readily appreciated by those of skill in the art. It is therefore to be understood that, within the scope of the appended claims, the invention may be practiced otherwise than as specifically described above.