Patent Document

This application is a continuation of application Ser. No. 09/318,404, filed on May 25, 1999, now U.S. Pat. No. 6,330,618, which is a continuation of application Ser. No. 08/792,166, filed Jan. 30, 1997, now U.S. Pat. No. 6,006,274. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to the field of portable computers systems. Specifically, the present invention discloses a systems for synchronizing a portable computer system with a desktop computer system. 
     BACKGROUND OF THE INVENTION 
     Personal computer systems have become common tools in modem society. To organize their lives, many personal computer users use Personal Information Management (PIM) applications such as an address book, a daily organizer, and a To-Do list application on their personal computers. Although such Personal Information Management applications have proven useful, their utility is limited by the fact that the person must be sitting their personal computer system to access the information. 
     To remedy this limitation, many palmtop computer organizers have been introduced. A palmtop computer organizer is a computer that is small enough to be held in the hand of a user and runs Personal Information Management (PIM) applications such as an address book, a daily organizer, and electronic notepads. Examples of palmtop computer organizers include the Sharp® Zaurus, the Apple® Newton®, and the Tandy® Zoomer™. 
     However, the palmtop organizers also suffer from a number of limitations. Entering information into a palmtop organizer is usually performed by typing on a keyboard that is too small for normal typing, or by writing onto a digitizer with a stylus and relying on handwriting recognition software. Backing up the information on a palmtop organizer is often a difficult and time consuming task requiring special cables and software. Printing the information stored within a palmtop organizer system is difficult since special printer cables must connect the palmtop organizer to a printer. 
     SUMMARY AND OBJECTS OF THE INVENTION 
     It is therefore an object of the present invention to provide an easy to use palmtop computer system that is well integrated with a personal computer system. By tightly integrating the palmtop computer system with a personal computer system, an already existing computer infrastructure can easily be used by the palmtop computer system. To integrate to the computer system, the present invention teaches synchronization of information on the palmtop computer system and the personal computer system. 
     To integrate the palmtop computer system with a personal computer system in a user friendly manner, the palmtop computer system must be able to handle many different synchronization environments. The palmtop computer system should handle the different synchronization environments in a manner that requires very little user interaction. Thus, the palmtop computer system and the personal computer system must automatically recognized the synchronization environment and perform the synchronization. 
     Different synchronization environments include: synchronizing multiple palmtop computer systems with a single personal computer system; synchronizing a single palmtop computer system with multiple personal computer systems; synchronizing a palmtop computer system with a remote personal computer system across a network using a local personal computer system; and remotely synchronizing with a personal computer system across a telephone line. The software architecture of the present invention recognizes each of these different synchronization environments and performs the synchronization of information appropriately. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The objects, features, and advantages of the present invention will be apparent from the following detailed description of the preferred embodiment of the invention with references to the following drawings. 
     FIG. 1 illustrates a two portable computer systems and two personal computer systems equipped with cradles for synchronizing with the portable computer systems. 
     FIG. 2 illustrates a flow diagram that describes how a portable computer system acquires the identification information required to properly perform synchronizations in various environments. 
     FIG. 3 illustrates a flow diagram that describes how to obtain an address for a preferred synchronization personal computer system. 
     FIG. 4 illustrates a block diagram that depicts the software architecture for synchronizing a portable computer through a first personal computer to a second personal computer using a network. 
     FIGS. 5 a ,  5   b , and  5   c  illustrate a flow diagram that depicts the beginning of the synchronization between a portable computer system and a personal computer system. 
     FIG. 6 a  illustrates a block diagram that depicts the software architecture for synchronizing a portable computer with a personal computer using two modems and the Public Switched Telephone Network (PSTN). 
     FIG. 6 b  illustrates a block diagram that depicts the software architecture for synchronizing a portable computer with a personal computer using a PPP connection between the portable computer system and a network coupled to the personal computer. 
     FIG. 7 illustrates a block diagram that depicts the software architecture for synchronizing a portable computer with a personal computer using a PPP connection between the portable computer system and an Internet Service Provider (ISP). 
    
    
     DETAILED DESCRIPTION 
     Methods and apparatus for implementing a palmtop computer system that is well integrated with a personal computer system is disclosed. In the following description, for purposes of explanation, specific nomenclature is set forth to provide a thorough understanding of the present invention. However, it will be apparent to one skilled in the art that these specific details are not required to practice the present invention. In other instances, well-known circuits and devices are shown in block diagram form to avoid obscuring the present invention. 
     Basic Synchronization 
     FIG. 1 illustrates a portable computer system  130 . The portable computer system  130  may execute a number of different computer programs. However, the most common applications on the portable computer system  130  will consist of a suite of Personal Information Management (PIM) applications such as an addressbook, a daily organizer, a To-Do list, and a memo pad. Most people that use a portable computer system  130 , also have a personal computer system that has the same applications. It would therefore be desirable to synchronize information between the portable computer system  130  and the personal computer system. 
     Also illustrated in FIG. 1 is a desktop personal computer system  110 . Coupled to the serial port  113  of the desktop personal computer system  110  is a cradle  120 . The cradle is used to provide a serial communication link between the portable computer system  130  and the personal computer system  110 . Specifically, the serial communication lines from the serial port  113  are extended and terminate at a serial connector  127  on the cradle  120 . A matching serial connector (not shown) on the portable computer system  130  connects the portable computer system  130  to the personal computer system  110 . 
     To synchronize the information between the portable computer system  130  and the personal computer system  110 , a user drops the portable computer system  130  into the cradle  120  and presses a synchronization button  125 . The synchronization button  125  causes a synchronization program on the portable computer system  130  to execute. The synchronization program on the portable computer system  130  wakes up a peer synchronization program on the personal computer system  110 . The synchronization program on the portable computer system  130  and the peer synchronization program on the personal computer system  110  perform the necessary operations to synchronize information stored on the two computer systems. The architecture of the synchronization process is described in the U.S. patent application entitled “Extendible Method and Apparatus for Synchronizing Multiple Files On Two Different Computer Systems” with Ser. No. 08/542,055, filed on Oct. 13, 1995, now U.S. Pat. 5,884,323. 
     To efficiently synchronize the information between the two computer systems, each system maintains a set of status flags for each of the data records. The status flags on each data record identify if the record is new, modified, or deleted. Thus, when a record on the portable computer system  130  or the personal computer system  110  is created, modified, or deleted, the status flags for that record are set to new, modified, or deleted respectively. The status flags on the data records greatly simplify the synchronization process since only the new, modified, or deleted records on each computer system need to be shared with the other computer system. After each synchronization, all the data record status flags are cleared since the two systems have identical databases after the synchronization point. 
     Synchronization of a Second Portable Computer System 
     As described in the previous section, a personal computer system can easily be equipped with a cradle  120  that allows a portable computer system  130  to synchronize with the personal computer system  110 . In this manner, the information on the portable computer system  130  can be backed-up on the personal computer system  110 . 
     Each personal computer system usually has ample resources for backing-up several portable computer systems. To back-up another portable computer system, such as portable computer  140 , the second portable computer system  140  can be placed into the same cradle  120 . When the synchronization button is pushed, the synchronization process begins. 
     In order to properly back-up the second portable computer system  140 , the personal computer system  110  needs to recognize that the second portable computer system  140  is different from the first portable computer system  130  such that the data from the first portable computer system  130  is not destroyed. To accomplish this goal, each portable computer system is assigned a name. Typically, the name of the portable computer system will be the same name as the user of the portable computer system. The name of the portable computer system is assigned when the portable computer system is first synchronized. 
     Then, when the second portable computer  140  system is inserted into the cradle and synchronized, the personal computer system  110  will recognize that a different portable computer system is being synchronize such that a different database will be used. The first time the second portable computer system  140  is synchronized, the personal computer will ask the user if a new account should be created on the personal computer system  110  for storing information from the second portable computer  140 . Thus, a second portable computer can be synchronized on a single personal computer. 
     Synchronization with a Second Desktop Computer System 
     The user of a portable computer system may work with more than one personal computer system. For example, many white collar workers that use a personal computer system at an office often have a second personal computer system at home. The second personal computer system allows the worker to work at night, work on weekends, or telecommute by working at home. It would be desirable to allow such a user to synchronize with both the personal computer at the office and the second personal computer system at home. 
     Referring to FIG. 1, a second personal computer system  150  with a second cradle  160  is illustrated. If the portable computer system  130  is placed into the second cradle  160  and the synchronization button  165  is pressed, then the portable computer system  130  will attempt to synchronize with the second personal computer system  150 . 
     As described in a previous section, the data records on the portable computer system  130  each have flags that specified if the record is new, modified, or deleted since the last synchronization. However, these flags are only relevant to the particular personal computer system that the portable computer system  130  last synchronized with. If the portable computer system  130  has been synchronized with a first personal computer system  110  and then the user later attempts to synchronize the portable computer system  130  with the second personal computer system  150 , then the status flags on the data records will only relate to the first personal computer system  110 . 
     Thus, an interesting problem is created when a portable computer system is synchronized with a first personal computer system, used, and then later synchronized with a second personal computer system. To handle the problem, the synchronization program on each personal computer system stores a copy of the reconciled database after each synchronization. The stored database copy is not modified. Then, when a synchronization must be performed wherein the new, modified, deleted record flags are not available, then the entire contents of the portable computer database is read and compared with the stored database. This comparison will yield a set of records that have been created (new), modified, or deleted since the last synchronization. These new, modified, and delete records can then be used to synchronize with the personal computer&#39;s current database. A detailed description of this technique can be found in the U.S. patent application entitled “Method and Apparatus for Synchronizing Information on Two Different Computer Systems” with Ser. No. 08/544,927, filed on Oct. 18, 1995, now U.S. Pat. No. 5,727,202. In this document, a synchronization that requires the copy of the database from the previous synchronization is known as a “slow sync.” 
     Before the problem of multiple synchronization hosts for a single portable computer can be solved, the problem first must be detected. To detect the problem of synchronizing with multiple personal computers, the portable computer creates a unique synchronization token after each synchronization. The synchronization token is stored by both the portable computer system and the personal computer system. Later, when a synchronization is attempted, the two systems compare synchronization tokens. If the synchronization tokens do not match, then the portable computer system&#39;s last synchronization was with a different personal computer system. In such situations, the reconciled database from the previous synchronization with this computer is fetched to perform the current synchronization. 
     SYNCHRONIZATION ACROSS A NETWORK 
     Personal computer systems are often coupled together into computer networks. When personal computer systems are coupled together into a network, each computer system can its share resources with the other computer systems coupled to the network. Similarly, each computer system can access the shared resources available from the other computer systems coupled to the network. 
     When a personal computer that is used to synchronize portable computers is coupled to a network, that network infrastructure can be used to route a synchronization to that “preferred” personal computer. For example, a user of a portable computer system will usually have a personal computer system that is “his” personal computer system. The user will store his personal data such his address lists, his personal calendar, and his To-Do list on his personal computer. New changes to the address list, calendar, and To-Do list will be made to his personal computer. It would therefore be desirable to always synchronize with his personal computer (a “preferred” computer). 
     Often, the user of a portable computer system will not be near his personal computer system. But if the user is near a personal computer that is coupled to his personal computer through a network, the user can synchronize with his personal computer using the network as a communication medium. To perform this synchronization across the network, the portable computer system must store an identifier that can be used to uniquely address the “preferred” personal computer across the network. 
     An example can be provided by referring again to FIG.  1 . In FIG. 1, two personal computers  110  and  150  are illustrated. The two personal computers  110  and  150  are coupled together using a computer network  180 . In one embodiment, the computer network  180  uses the TCP/IP suite of protocols. Personal computer  150  will be designated as the user&#39;s own personal computer (the “preferred” computer). If the user of portable computer system  130  is near personal computer  110  and wishes to synchronize with his personal computer system  150 , the user simply drops his portable computer system into the cradle  120  of the nearby personal computer  110  and presses the synchronization button  125 . The synchronization process then commences. 
     Using the identifier that uniquely addresses the “preferred” computer, the synchronization software in personal computer  110  attempts to reach the preferred computer across the network  180 . If the synchronization software in personal computer  110  can reach the preferred personal computer  150  through the network  180 , then the synchronization software in personal computer  110  simply acts as a pass-through and allows the synchronization software in personal computer  150  to perform the synchronization. This type of synchronization is referred to as a “net synchronization.” If personal computer  110  can not reach the preferred personal computer  150  through the network  180 , then the user may still synchronize with the local personal computer  110 . 
     Obtaining Synchronization Information 
     As described in the previous sections the present invention uses three pieces of identification information in order to synchronize properly: a portable computer user name; a net address of the personal computer; and a unique synchronization token. These three pieces of information are initialized when the portable computer system is first synchronized. The user name for the portable computer will remain static unless the user specifically requests a change. The net address of the personal computer may change due to a request by the user or an automatic update by the synchronization software. A new unique synchronization token is created every time the portable computer system is synchronized with a personal computer system. 
     FIG. 2 illustrates a flow diagram of an initialization that occurs during the first synchronization process of a portable computer system. The initialization occurs when the portable computer system is brand new and has never been used, or if all the information in the portable computer has been lost due to malfunction or complete battery discharge. 
     Referring to FIG. 2 the flow diagram starts where the Hot Sync Manager on the personal computer system is monitoring the serial port. (As described in previous sections, the synchronization may be performed with other communication means, but in most cases the first synchronization will be across a serial line.) Then, at step  215 , the portable computer requests a synchronization. At step  220 , the Hot Sync manager on the personal computer responds to the synchronization request by sending a request for the identification information on the portable computer system. At step  230 , the portable computer system sends empty identification fields back to the Hot Sync Manager program on the personal computer since the portable computer system is being used for the first time or has lost all of its information. 
     Since the portable computer system has not sent any identification information to the Hot Sync Manager, the portable computer system is indicating that it is brand new or it has lost its information because of failure. Thus, the Hot Sync Manager on the personal computer system first determines if there is any portable computer system back-up information on the personal computer at step  235 . If back-up information for a portable computer system exists on the personal computer, then at step  240  the Hot Sync Manager asks the user if he wishes to restore the portable computer system using the back-up information stored on the personal computer system. If the user requests to restore the portable computer from the back-up information, the Hot Sync Manager proceeds to step  250  where the portable computer system is restored using the back-up copy of information. Otherwise the system proceeds to step  260  where the process of initializing a new portable computer system begins. 
     The first step in initializing a portable computer is to request a name for the portable computer system as stated in step  260 . In one embodiment, the portable computer system simply asks for the name of the intended user. The user name is assigned to the portable computer system such that the portable computer system can be identified during future synchronizations. 
     Next, at step  265 , the Hot Sync Manager program attempts to obtain a network address for the personal computer system in order to have a “preferred” personal computer system. The Hot Sync Manager program attempts to obtain an IP address, a host name, and a SubNet Mask that will be used to locate the preferred personal computer system during future synchronization operations across a network. The user name and preferred personal computer network address are stored in the portable computer system at step  270 . Finally a unique synchronization token for this synchronization session is given to the portable computer system at step  275 . The unique synchronization token will be used next time the portable is synchronized to determine if it is being synchronized on the same computer system that it was last synchronized with. 
     FIG. 3 illustrates how the Hot Sync Manager Program obtains the network address information for the preferred personal computer. First at step  310  the Hot Sync Manager Program determines if the personal computer has TCP/IP services available. If the personal computer does not have TCP/IP protocol services then the Hot Sync Manager Program simply moves to the next step of the synchronization initialization. In an alternate embodiment, the Hot Sync program retrieves a host name for the personal computer name from a Windows registry. The host name from the registry is then later used to obtain the preferred personal computer address for synchronization operations across a network. 
     If the personal computer is running TCP/IP protocol, then the Hot Sync Manager proceeds to step  320  where the Hot Sync Manager obtains a host name. The host name may later be used with a Domain name service (DNS) in order to obtain an IP address for the preferred personal computer. After obtaining a host name then the Hot Sync Manager proceeds to step  330  where the Hot Sync Manager determines if the personal computer has been assigned an Internet Protocol (IP) address. If the personal computer has been assigned a IP address then that IP address is stored for future use. Finally, the Hot Sync Manager proceeds to step  340  and attempts to obtain a SubNet Mask. 
     The Synchronization Process 
     Once a portable computer system has been initialized with the proper information, the portable computer system can be synchronized with a main desktop personal computer system in a number of different ways. This section will describe how the portable computer systems synchronizes with the personal computer system with reference to the block diagram in FIG.  4  and the flow diagram in FIG.  5 . 
     FIG. 4 illustrates a block diagram of a portable computer system coupled to a personal computer through a serial line for synchronization. The personal computer  420  is also connected to a local area network  450 . Other personal computers such as preferred personal computer  460  are also coupled to the network. The portable computer  410  can synchronize either with the local personal computer  420  or the preferred personal computer  460  across the network. 
     FIG. 5 illustrates a flow diagram that describes an embodiment of the synchronization process in detail. Specifically, FIG. 5 describes most of the steps performed by one embodiment of the Hot Sync Manager program  421  to determine the synchronization environment. Initially the portable computer systems sends a synchronization request at step  505 . In the case where the portable computer  410  is synchronizing through a cradle as illustrated in FIG. 4, the synchronization request is carried across the serial line to the local personal computer  420 . The personal computer  420  recognizes the synchronization request packet and responds by sending a request for additional information from the portable computer system  410  at step  507   
     In response to the request for additional information, the portable computer  410  sends the three items of identification information as previously described. Specifically, the portable computer system  410  sends the personal computer system  420  the portable system&#39;s name, a network address of the preferred personal computer, and the synchronization token received during the previous synchronization at step  509 . At step  510  the synchronization program first checks the last synchronization token to determine if this is the same personal computer that the portable computer last synchronized with. If this is the same personal computer that the portable computer last synchronized with, then the Hot Sync Program immediately performs a fast synchronization at step  515 . 
     If this is not the personal computer that the portable computer most recently synchronized with then the synchronization manager program proceeds to step  525  where it determines if network address information is available for both the personal computer  420  on which the Hot Sync Program is running and the “preferred” personal computer requested by the portable computer system. 
     If network address information is not available for both the current personal computer and the desired personal computer, then the Hot Sync Manager proceeds to step  527  where it may attempt to do some type of local synchronization. At step  527 , the Hot Sync manager determines if an account for this portable computer exists on this personal computer. If an account exists on this personal computer for the portable then the Hot Sync Manager proceeds to step  530  where a slow synchronization is performed using the last synchronization information available for the portable computer system. If the account for this portable does not exist, the user is asked if a new account should be created at step  580 . 
     If at step  525 , the Hot Sync Manager determines that the network address information is available for both the current personal computer and the portable&#39;s preferred personal computer, then the synchronization process proceeds to step  540 . At step  540  the network address of the local personal computer is compared with the network address information of the preferred personal computer. If the two addresses match, then this is the preferred personal computer but portable computer was last synchronized with another personal computer system. In such a situation, the Hot Sync Manager performs a slow synchronization using the information stored from the last synchronization with this personal computer at step  530 . 
     If this is not the preferred the personal computer then the Hot Sync Manager proceeds to step  550  to determine if TCP/IP services are available on this personal computer. If TCP/IP services are not available then a synchronization across a network cannot be performed. Thus, the Hot Sync Manager proceeds to step  565  to determine if a local account for this portable exists. If an account exists, a slow synchronization is performed using the information stored from the last synchronization performed with this personal computer. If no local account exists then the user will be asked if a new account should be created. 
     However, if this is not the preferred personal computer and TCP/IP services are available, then the Hot Sync Manager will look across the network for the preferred personal computer at step  555 . If the preferred personal computer can be contacted across the network then the synchronization will be performed with the preferred personal computer across the network. In this situation the local Hot Sync Program  421  merely acts as a pass-through such that all synchronization information passes from the local Hot Sync Program  421  to the remote Hot Sync Program  461  on the preferred personal computer  460 . Thus, the remote Hot Sync Program  461  takes over the Synchronization process and performs a fast sync or slow sync as necessary. 
     Remote Synchronization 
     A person traveling with a portable personal computer system may want to synchronize with a desktop personal computer system while on the road. For example, a traveling executive may wish to receive calendar updates that have been placed into his personal computer by an administrative assistant. One architecture for remotely synchronizing with a desktop personal computer is illustrated in FIG.  6 A. 
     Referring to FIG. 6A, the portable computer  610  with its Hot Sync Program  615  is coupled to a modem  630 . The Hot Sync Program  615  is configured such that it can initialize the modem  630  and dial another computer system. 
     Also illustrated in FIG. 6A is a personal computer system  660  with a Hot Sync Manager Program  661  and a Hot Sync database  663 . To monitor for remote synchronizations the Hot sync Manager can be instructed to listen to a serial line coupled to a modem  669 . If a ring signal is detected by the modem  669  the Hot Sync Manager  661  will answer the call and attempt to begin a synchronization with a remote portable computer system  610 . 
     To synchronize remotely, the Hot Sync Program  615  on the portable computer  610  configures the modem  630  and dials the modem  669  coupled to desired personal computer  660 . The modem  669  notices the ringing phone and informs the Hot Sync Manager  661  on the personal computer  660 . The Hot Sync Manager program  661  response by instructing the modem  669  to answer the call. Once the call has been answered, the Hot Sync Manager program  661  listens for a synchronization token. When the Hot Sync Program  615  in the portable computer system  610  notices the call has been answered by another modem, the Hot Sync Program  615  in the portable computer system  610  sends a synchronization request token to the computer that answered. The Hot Sync Manager  661  responds to the synchronization request token by requesting the identification information from the portable computer system  610 . The synchronization progresses as described in the previous sections. 
     Although the remote synchronization system illustrated in FIG. 6A is very useful, it suffers from a few drawbacks. The synchronization system illustrated in FIG. 6A requires a dedicated telephone line and a modem for the Hot Sync Manager  661  on the preferred personal computer  660 . Furthermore, the modem  669  is only used to listen for synchronization requests. Additionally, if the user with the portable computer  610  is far away from the personal computer system  660  then a long-distance toll call will be required to synchronize with the personal computer system  660 . Therefore an alternate system of remote synchronization is desirable. 
     FIG. 6B illustrates an alternate embodiment of the remote synchronization system. In the alternate embodiment of FIG. 6B, the Hot Sync Program  615  communicates through a TCP/IP stack  617  with a Serial Line Internet Protocol (SLIP) or Point-to-Point Protocol (PPP) client program  619  before communicating with modem  630 . Thus, by using the TCP/IP stack  617  and a SLIP or PPP client program  619 , the Hot Sync Program  615  in FIG. 6B attempts a remote synchronization by performing a net synchronization across a SLIP or PPP link. 
     To remotely perform a net synchronization, the Hot Sync Program  615  first establishes a SLIP or PPP link with a server that is coupled to the same network as the preferred personal computer. Thus, the SLIP/PPP software using the modem  630  to dial and connect to a modem  641  on a remote access server  640 . A SLIP/PPP server process  643  on the remote access server  640  will answer the call and establish a SLIP/PPP session. Once the SLIP/PPP session has been created the Hot Sync Program  615  can use the network address of the preferred personal computer to access the Hot Sync Manager Program on the preferred personal computer that is coupled to the TCP/IP Local Area Network  650 . The Hot Sync Manager in the preferred personal computer will be monitoring the TCP/IP packets for a synchronization request across the TCP/IP LAN. If the Hot Sync Manager  661  on the preferred personal computer gets such a synchronization request packet, then the Hot Sync Manager  661  begins a synchronization with the portable computer system. 
     The TCP/IP based remote synchronization system can be performed using the global Internet. FIG. 7 illustrates an example of a portable computer system  710  synchronizing with a preferred PC  760  across the global Internet  780 . Specifically the Hot Sync Program  715  in the global computer system establishes a PPP or SLIP connection with an Internet Service Provider (ISP)  740 . The SLIP/PPP session is established between the SLIP/PPP client on the portable computer system  710  and a SLIP/PPP server  743  at the ISP  740 . The SLIP/PPP server at the ISP  740  can communicate across the global Internet to any Internet addressable location. Thus, if the network address of the preferred personal computer  760  is accessible through the global internet  780  then the global computer system  710  can communicate with the preferred personal computer  716  to perform a remote synchronization. 
     Many businesses, however, install firewall servers or gateway servers  790  on their Local Area Network as illustrated in FIG.  7 . The firewall server acts as a protection mechanism to protect the internal Local Area Network  750  of a company from attacks by unscrupulous Internet users. One method of protecting the internal Local Area Network is to require any communication with the global Internet to pass through a proxy application. In FIG. 7, proxy applications  791 ,  792  and  793  are used to bridge various communication protocols. Each proxy application filters the packets associated with its respective protocol before allowing the packets to access the internal Local Area Network  750 . If such firewall system is installed at the corporation of a user who wishes to synchronize a portable computer, then a proxy application for the specific synchronization protocol may be required. 
     Although the present invention has been described in terms of specific exemplary embodiments, it will be appreciated that various modifications and alterations might be made by those skilled in the art without departing from the spirit and scope of the invention as set forth in the following claims.

Technology Category: y