CROSS REFERENCE TO RELATED APPLICATIONS 
   This application is the US National Stage of International Application No. PCT/DE03/02775, filed Aug. 20, 2003 and claims the benefit thereof. The International Application claims the benefits of German application No. 10241957.4 DE filed Sept. 10, 2002, both of the applications are incorporated by reference herein in their entirety. 
   FIELD OF INVENTION 
   The invention relates to a data communication system, a computer for use in a data communication system of said type, and a method for updating software stored on a computer of a data communication system according to the claims. 
   BACKGROUND OF INVENTION 
   The transmitting of data over the internet continues to increase in significance. The internet is a global data network or, expressed more precisely, comprises a plurality of different data networks interconnected my means of, for example, what are termed routers. 
   In each case one or more central computers, referred to in the relevant literature frequently as servers, communicate within the internet with clients located remotely from them, for example with a (stationary or portable) computer, a telephone, etc., and/or with further, central computers. Communication takes place using what are termed internet protocols, in particular the TCP/IP Protocol (Transmission Control Protocol/Internet Protocol). Software (what is termed a socket or TCP/IP stack) able to understand and evaluate the TCP/IP Protocol is loaded for this purpose on, for example, the respective client. 
   An increasing number of private data networks, which is to say data networks that can only be used by specific, authorized persons, are based on the technology and concept of the internet. Data networks of said type are referred to in the relevant literature as intranets. Within an intranet, in a manner analogous to the internet a relevant central computer, for example, communicates using internet protocols, in particular the TCP/IP Protocol, with clients located remotely from it, for example (stationary or portable) computers, telephones, etc. (and/or with further, central computers). For transmission, the relevant intranet data is divided in each case into individual packets then sent in an asynchronous manner. 
   Intranets are generally connected to the telephone network via the relevant, central computer, so are able to communicate with a further computer over the telephone network. 
   Data communication over the telephone network can take place on the basis of, for example, POTS (Plain Old Telephone Service) data transmission protocols or ISDN (Integrated Services Digital Network) data transmission protocols; alternatively on the basis of xDSL (x Digital Subscriber Line) data transmission protocols, for example by means of ADSL (ADSL=Asynchronous Digital Subscriber Line) data transmission. A plurality of frequency bands are employed in the case of data communication according to an xDSL protocol which are above the frequency bands used for POTS data transmission or, as the case may be, ISDN data transmission. 
   If the software loaded on a central intranet computer is to be updated, a further computer that initiates software updating can establish a POTS connection or an ISDN connection to the central intranet computer over the telephone network then transmit the software files required for updating to said central intranet computer. 
   The central intranet computer, and hence also the intranet clients connected thereto, for example the above-cited computers, telephones, etc. (and/or the further central computers connected to the central intranet computer) can additionally also be connected to the internet. The relevant central intranet computer can herein, for example, be continually connected to the internet (which is to say always on line). Central intranet computers of said type or, as the case may be, the intranet clients connected thereto have as a rule permanent IP (Internet Protocol) addresses consisting of a multi-digit number. Via the relevant address, other computers connected to the internet can establish a connection to the central intranet computer or, as the case may be, to the intranet clients connected thereto. 
   Other central intranet computers are not continually connected to the internet (which is to say are not always on line). Said computers or, as the case may be, the intranet clients connected thereto will be able to receive a temporary IP address assigned by the respective central (or any other) computer if they establish a connection to the internet (using, for example, a POTS, ISDN, or xDSL data transmission protocol) with, for instance, a corresponding central computer of an internet provider having been intermediately connected. Unlike in conventional telephone networks, there is thus in this case no fixed assignment between the respective device (here: the relevant central computer or, as the case may be, intranet client) and the call identification (here: an IP address consisting of a multi-digit number). 
   SUMMARY OF INVENTION 
   The object of the invention is to provide a novel data communication system, a novel computer, and a novel method for updating software stored on a computer of a data communication system. 
   The invention achieves this and further objects by means of the subjects of independent claims. 
   Advantageous developments of the invention are indicated in the dependent claims. 
   According to a basic concept underlying the invention, a data communication system having a plurality of computers and one administrative computer is provided wherein, prior to the updating of software stored on one of the computers or, as the case may be, on a storage device assigned thereto, data indicating which transmission medium is to be used for exchanging data used for updating or, as the case may be, for controlling the updating process is exchanged between the respective computer and the administrative computer. 
   Which transmission medium is to be used for exchanging data used for updating or, as the case may be, for controlling the updating process is particularly advantageously ascertained by the respective computer or, as the case may be, by special software-updating control software stored on the respective computer or, as the case may be, on the storage device assigned thereto. 
   The data used for updating or, as the case may be, for controlling the updating process can thereby be transmitted, adaptively, in each case over the (momentarily) optimal transmission medium using in particular the specific communication path over which the maximum data rate is (momentarily) achievable. 


   
     BRIEF DESCRIPTION OF THE DRAWING 
     The invention is explained in more detail below with the aid of an exemplary embodiment and the attached drawing. 
       FIG. 1 : is a schematic of a data communication system according to an exemplary embodiment of the invention. 
   


   DETAILED DESCRIPTION OF INVENTION 
   In the data communication system  1  shown in  FIG. 1  a plurality of clients  2   a ,   2   b ,  2   c ,  3   a ,  3   b  (a plurality of telephones  3   a ,  3   b  and a plurality of computers  2   a ,  2   b ,  2   c  in the present exemplary embodiment) are connected to a first intranet data network A. 
   The first intranet data network A has a telecommunication system or, as the case may be, a central computer  5  functioning as a telecommunication system, which computer functions for the clients  2   a ,  2   b ,  2   c ,  3   a ,  3   b  as a communication-control device, in particular as a telephone switching system, for connecting the first intranet data network A (or, as the case may be, the clients  2   a ,  2   b ,  2   c ,  3   a ,  3   b  connected thereto) to a telephone network (for example to the public telephone network). 
   Communication-control software is for this purpose loaded in a manner known per se on a storage device  8  of the central computer  5 . 
   The central computer  5  or, as the case may be, the clients  2   a ,  2   b ,  2   c ,  3   a ,  3   b  are connected to the first intranet data network A my means of lines  6   a ,  6   b ,  6   c ,  7   a ,  7   b ,  9  connected to a corresponding bus system. 
   The clients  2   a ,  2   b ,  2   c ,  3   a ,  3   b  and the central computer  5  communicate using internet protocols, for example the Transmission Control Protocol (TCP) or, as the case may be, the Internet Protocol (IP). Software (what is termed a stack) able to understand and evaluate the relevant internet protocol is for this purpose loaded on the respective client  2   a ,  2   b ,  2   c ,  3   a ,  3   b  or, as the case may be, on the central computer  5 . 
   To transmit data between the clients  2   a ,  2   b ,  2   c ,  3   a ,  3   b  and the central computer  5  over the first intranet data network A, the data is divided, as is customary in the case of internet protocols, into individual packets. 
   If one of the clients  2   a ,  2   b ,  2   c ,  3   a ,  3   b  communicates over the telephone network with an external device not connected directly to the first intranet data network A (with the telephone  10   a  device in the present exemplary embodiment), the data will be converted by the central computer  5  into corresponding POTS data or ISDN data and fed out to the telephone network over a line  11 . Vice versa, the POTS data or, as the case may be, ISDN data received over the telephone network by the telephone  10   a  will be forwarded in the above-cited manner by the central computer  5  to the respective client  2   a ,  2   b ,  2   c ,  3   a ,  3   b  over the first intranet data network A. 
   As is further shown in the FIGURE, the data communication system  1  has a plurality of further intranet data networks apart from the first intranet data network A. A second intranet data network B and a third intranet data network C are shown in the present exemplary embodiment. 
   The second intranet data network B has, analogously to the first intranet data network A, a plurality of clients  12   a ,  12   b ,  12   c ,  13   a ,  13   b , namely telephones  13   a ,  13   b  and computers  12   a ,  12   b ,  12   c  in the present exemplary embodiment. 
   As well as to a telephone network, the second intranet data network B can also be connected to the internet. Connection to the internet is effected over the telephone network and via a computer  15   b  of an internet service provider (ISP for short). 
   The second intranet data network B has a telecommunication system or, as the case may be, a central computer  15   a  functioning for the clients  12   a ,  12   b ,  12   c ,  13   a ,  13   b  as a communication-control device, in particular as a switching system for connecting the second intranet data network B (or, as the case may be, the clients  12   a ,  12   b ,  12   c ,  13   a ,  13   b  connected thereto) to the telephone network. The central computer  15   a  furthermore connects the second intranet data network B to the internet, with the telephone network being connected intermediately. The central computer  15   a  is not herein connected permanently to the internet, which is to say is not always on line. 
   Communication-control software is loaded in a manner known per se on a storage device  18  of the computer  15   a  to control communication between the clients  12   a ,  12   b ,  12   c ,  13   a ,  13   b  and the telephone network or, as the case may be (if required) with the internet. 
   The central computer  15   a  or, as the case may be, the clients  12   a ,  12   b ,  12   c ,  13   a ,  13   b  are connected to the second intranet data network B by means of lines  16   a ,  16   b ,  16   c ,  17   a ,  17   b ,  19   a  connected to a corresponding bus system. 
   The clients  12   a ,  12   b ,  12   c ,  13   a ,  13   b  and the central computer  15   a  communicate using internet protocols, for example the Transmission Control Protocol (TCP) or, as the case may be, the Internet Protocol (IP). Software (what is termed a stack) able to understand and evaluate the relevant internet protocol is for this purpose loaded on the respective client  12   a ,  12   b ,  12   c ,  13   a ,  13   b  or, as the case may be, on the central computer  15   a.    
   If one of the clients  12   a ,  12   b ,  12   c ,  13   a ,  13   b  communicates with an external device which is not connected directly to the second intranet data network B but is connected to the telephone network (with a telephone  10   b  device in the present exemplary embodiment), the data will be converted by the central computer  15   a  into corresponding POTS data or ISDN data and fed out to the telephone network over a line  19   b . Vice versa, the POTS data or, as the case may be, ISDN data received over the telephone network by the telephone  10   b  will be forwarded in the above-cited manner by the central computer  15   a  to the respective client  12   a ,  12   b ,  12   c ,  13   a ,  13   b  over the second intranet data network B. 
   If, by contrast, one of the clients  12   a ,  12   b ,  12   c ,  13   a ,  13   b  is to communicate with a device connected to the internet (with a computer  10   c  device in the present exemplary embodiment), a telephone connection (for example a POTS, ISDN, or xDSL connection, in particular an ADSL connection) will be set up by the central computer  15   a  to the ISP computer  15   b , which will then assign a temporary IP address to the central computer  15   a  or, as the case may be, the respective client  12   a ,  12   b ,  12   c ,  13   a ,  13   b . The ISP computer  15   b  will furthermore initiate the establishment of a corresponding internet connection so that data can be exchanged between the respective client  12   a ,  12   b ,  12   c ,  13   a ,  13   b  and the computer  10   c  over the internet and the telephone network, with the ISP computer  15   b  and the central intranet computer  15   a  having been intermediately connected. 
   The number of IP addresses to be administered by the ISP computer  15   b  is reduced through the use of temporary IP addresses instead of IP addresses permanently assigned to a specific central computer or, as the case may be, client. 
   As is further shown in the FIGURE, the third intranet data network C has, analogously to the first and second intranet data network A, B, a plurality of clients  22   a ,  23   a , namely a telephone  23   a  and a computer  22   a  in the present exemplary embodiment. 
   The third intranet data network C is connected to the telephone network and additionally to the internet. In contrast to the second intranet data network B, the third intranet data network C is connected directly and continually to the internet by means of a corresponding dedicated line  29   c.    
   The third intranet data network C has a telecommunication system or, as the case may be, a central computer  25  functioning as a telecommunication system, which computer functions for the clients  22   a ,  23   a  as a communication-control device, in particular as a switching system, for connecting the intranet data network (or, as the case may be, the clients  22   a ,  23   a  connected thereto) to the telephone network or the internet. The central computer  25  is permanently connected to the internet over the dedicated line  29   c  (which is to say is always on line). 
   Communication-control software is loaded in a manner known per se on a storage  28  of the computer  25 . 
   The central computer  25  or, as the case may be, the clients  22   a ,  23   a  are connected to the third intranet data network C by means of lines  26   a ,  27   a ,  29   a  connected to a corresponding bus system. 
   The clients  22   a ,  23   a  and the central computer  25  communicate using internet protocols, for example the Transmission Control Protocol (TCP) or, as the case may be, the Internet Protocol (IP). Software (what is termed a stack) able to understand and evaluate the relevant internet protocol is for this purpose loaded on the respective client  22   a ,  23   a  or, as the case may be, on the central computer  25 . 
   If one of the clients  22   a ,  23   a  communicates with an external device which is not connected directly to the intranet data network but is connected to the telephone network (with the telephone  10   a  device in the present exemplary embodiment), the data will be converted by the central computer  25  into corresponding POTS data or ISDN data and fed out to the telephone network over a line  29   b . Vice versa, the POTS data or, as the case may be, ISDN data received over the telephone network by the telephone  10   a  will be forwarded in the above-cited manner by the central computer  25  to the respective client  22   a ,  23   a  over the third intranet data network C. 
   The central intranet computer  25  or, as the case may be, the clients  22   a ,  23   a  connected thereto have a permanent IP address consisting of a multi-digit number so that, following establishment of the corresponding internet connection, data can be exchanged between a device connected to the internet (for example the computer  10   c ) and the central computer  25  or, as the case may be, between the device (for example the computer  10   c ) and the respective client  22   a ,  23   a , with, in that case, the computer  25  having been intermediately connected. 
   An administrative computer  31  (here: a PC, standing for Personal computer) and a server computer  4  (here: a TFTP, standing for Trivial File Transfer Protocol, server computer) is provided in the present exemplary embodiment for updating the communication-control software stored on the storage devices  8 ,  18 ,  28  of the central computers  5 ,  15   a ,  25  (or for updating any other software stored on the relevant storage devices  8 ,  18 ,  28 ). Any other server computer, for example an ordinary web server computer, in particular an HTTP server computer or, as the case may be, HTTPS server computer, can also be used instead of a TFTP server computer. 
   The server computer  4  and/or the administrative computer  31  can be located remotely from each other and/or remotely from some or all of the central computers  5 ,  15   a ,  25 . 
   Updating of the software on the central computers  5 ,  15   a ,  25 , in particular exchanging of the data required therefore, takes place in the data communication system  1  shown in an adaptive manner, in particular in a manner ensuring as fast as possible a data transmission rate. 
   As can be seen from the FIGURE and the description, all central computers  5 ,  15   a ,  25  are accessible over the telephone network, which is to say via a call identification permanently assigned to the respective computer  5 ,  15   a ,  25  (here: a telephone number). Only some of the central computers, namely the central computers  15   a  and  25 , are by contrast accessible over the internet. 
   Stored on a storage device  32  of the administrative computer  31  is a list of those central computers  5 ,  15   a ,  25  or, as the case may be, the call identifications assigned thereto, whose software can be updated in a process initiated from the administrative computer  31 . 
   In the present exemplary embodiment the administrative computer  31  is connected to the telephone network and (temporarily or in a stationary manner) to the internet via corresponding lines  33   a ,  33   b ,  33   c . 
   The respective central computer  5 ,  15   a ,  25  for which software updating is to be performed can be selected by means of appropriate selection entries made on the administrative computer  31  by a user P. A telephone connection, in particular a POTS or ISDN telephone connection, will then be set up to the selected central computer  5 ,  15   a ,  25  automatically initiated by the administrative computer  31 . This is done by dialing the telephone number, contained in the list, assigned to the respective computer  5 ,  15   a ,  25 . 
   Special, separate software-updating control software is stored on the corresponding storage devices  8 ,  18 ,  18  of the central computers  5 ,  15   a ,  25 . Said software-updating control software can alternatively also be integrated in, for example, other software components, for example the communication-control software, stored on the respective storage device  8 ,  18 ,  18 . 
   The software-updating control software will be launched once a telephone connection has been set up between the respective central computer  5 ,  15   a ,  25  and the administrative computer  31  (see step K or, as the case may be, arrow K). Said control software will then ascertain which communication paths are momentarily available to the respective central computer  5 ,  15   a ,  25 . The central computer can, for example (as is the case, for instance, with the central computer  5 ), be embodied or, as the case may be, set up solely for communicating over a corresponding telephone connection, routed in this case over the line  11 . The relevant central computer can alternatively (as is the case, for instance, with the central computer  25 ) be additionally connected to the internet, which is to say embodied or, as the case may be, set up in such a way as to be able to communicate permanently over a corresponding internet connection. 
   It is also possible for the relevant central computer to be embodied or, as the case may be, set up (as is the case, for instance, with the central computer  15   a ) for communicating over a corresponding telephone connection and additionally to be capable of being connected to the internet but momentarily not to be connected thereto (offline condition). The relevant central computer will then momentarily not be able to communicate over the internet. The software-updating control software can in this case initiate the immediate connection of the central computer  15   a  to the internet. 
   The relevant central computer can furthermore be embodied or, as the case may be, set up (as is the case, for instance, with the central computer  15   a ) for communicating over a corresponding telephone connection and be momentarily (but not continually) online, which is to say connected to the internet (or can be put into such a condition in the above-described manner initiated by the software-updating control software). The relevant central computer will then momentarily be able to communicate over a corresponding internet connection. 
   When the communication paths momentarily available to the respective central computer  5 ,  15   a ,  25  have been ascertained, then, if it has been ascertained that several communication paths are available, one of said ascertained communication paths will be selected by the software-updating control software, in particular the one over which momentarily the fastest data rate can be achieved. 
   The ascertained result is then, initiated by the software-updating control software, notified to the administrative computer  31  by means of corresponding data exchanged over the telephone connection existing between the respective central computer  5 ,  15   a ,  25  and the administrative computer  31 . This takes place in particular by means of data identifying the type of selected communication path (POTS telephone connection or, as the case may be, ISDN telephone connection/fixed IP connection/temporary IP connection) and/or by means of data identifying the call identification (telephone number/fixed IP address/temporary IP address) assigned to the selected communication path. 
   If the selected communication path does not correspond to the communication path used momentarily for communication between the respective central computer  5 ,  15   a ,  25  and the administrative computer  31  (which is to say to the above-cited telephone connection), then, initiated by the administrative computer  31  or, alternatively, by the respective central computer  5 ,  15   a ,  25 , a new connection will be set up between the administrative computer  31  and the respective central computer  25 . For example an internet connection will be set up (see step L or, as the case may be, arrow L) using the conveyed (fixed or temporary) IP address. 
   Further data relating to the control of the updating process of the (communication-control) software stored on the storage device  8 ,  18 ,  28  of the respective central computer  5 ,  15   a ,  25  is then exchanged between the respective central computer  5 ,  15   a ,  25  and the administrative computer  31  over the selected communication path, which is to say either over the new communication path or, if the original communication path corresponds to the selected communication path, over the communication path originally existing between the respective central computer  5 ,  15   a ,  25  and the administrative computer  31 . 
   Said (updating-process control) data can indicate:
         the precise time at which updating is to be performed, and/or   the (communication-control) software version momentarily stored on the respective storage device  8 ,  18 ,  28 , and/or   information on whether all the (communication-control) software or only individual components of the (communication-control) software is/are to be updated or, as the case may be, which components are to be updated, and/or   the communication path over which communication is to take place with the server computer  4  (this communication path can correspond, for example, to the selected communication path), and/or   depending on the respectively indicated communication path, the corresponding call identification of the server computer  4 , in particular its telephone number, IP address, or URL, and/or,   the path or, as the case may be, file name(s) under which the relevant files required for updating the (communication-control) software are stored on the server computer  4 .       

   A part of the (updating-process control) data, for example the data indicating which precise software components are to be updated, can be entered or, as the case may be, selected by the user P on the administrative computer  31 , in particular (when the data is transmitted over the internet) by means of appropriate entries made on a browser displayed thereon. 
   Other (updating-process control) data can be stored in advance on, for example, the storage device  32  of the administrative computer  31  or can be ascertained by means of corresponding control software stored on the storage device  32  of the administrative computer  31  (for example the corresponding call identification, in particular the telephone number or IP address or, as the case may be, URL of the server computer  4 ), and/or can be stored in advance on the respective storage device  8 ,  18 ,  28  of the corresponding central computer  5 ,  15   a ,  25  or ascertained by means of the corresponding control software stored on the respective storage device  8 ,  18 ,  28  of the corresponding central computer  5 ,  15   a ,  25  (for example the data identifying the communication path to be used for communicating with the server computer  4 ). 
   A connection is thereupon set up through a process initiated by the respective central computer  5 ,  15   a ,  25 , in particular by the software-updating control software, over the selected communication path between the respective central computer  5 ,  15   a ,  25  and the server computer  4 . This takes place, for example, proceeding from the central computer  15   a  or  25  using the IP address or, as the case may be, URL (see step N or, as the case may be, arrow N) conveyed by the administrative computer  31  or proceeding from the central computer  5  using the telephone number (see step M or, as the case may be, arrow M) conveyed by the administrative computer  31 . 
   Further (updating-process control) data is exchanged between the respective central computer  5 ,  15   a ,  25  and the server computer  4  when the corresponding connection has been set up. Said further (updating-process control) data can indicate, for example, the path or, as the case may be, file name(s) of the file or, as the case may be, files requiring to be transmitted to the respective central computer  5 ,  15   a ,  25  for updating the (communication-control) software, and/or the precise time at which the corresponding files are to be conveyed. 
   The corresponding file(s) stored, for example, on a storage device  34  of the server computer  4  is/are then transmitted to the respective central computer  5 ,  15   a ,  25  over the corresponding connection. The (communication-control) software is then updated there in a manner known per se under the control of the software-updating control software and using the file(s) conveyed by the server computer  4 . 
   Data identifying the status of updating (for instance data indicating whether updating could or could not be performed successfully) is thereupon conveyed, for example initiated by the software-updating control software, over the connection existing between the respective central computer  5 ,  15   a ,  25  and the administrative computer  31  (or, alternatively, over a connection then newly set up) from the respective central computer  5 ,  15   a ,  25  to the administrative computer  31 . This takes place using an administrative-computer-updating status-conveying destination address which, as part of the (updating-process control) data, has been conveyed in advance to the respective central computer  5 ,  15   a ,  25  by the administrative computer  31 . 
   One or more of the intranet data networks A, B, C can, in an alternative exemplary embodiment, be connected to further intranet data networks over corresponding lines and corresponding, further central computers (here, for example, the intranet data network A over lines  9   a ,  9   b  and further central computers  5   a ,  5   b ), which is to say can be combined therewith into an aggregate network. 
   Stored on corresponding storage devices  8   a ,  8   b  of the further central computers  5   a ,  5   b  is communication-control software corresponding to the communication-control software stored on the storage device  8  of the central computer  5  or, as the case may be, being identical thereto. 
   The respective central computer (in this case the central computer  5 ) or, as the case may be, the software-updating control software stored on its storage device  8 , can then, with the aid of corresponding data exchanged with the further central computers  5   a ,  5   b  over the lines  9   a  or, as the case may be,  9   b , cause the communication-control software stored on the storage devices  8   a ,  8   b  of the further central computers  5   a ,  5   b  to be updated accordingly, as, previously, the communication-control software stored on the storage device  8  of the central computer  5 . This is done by means of forwarding by the central computer  5  of the corresponding file(s) required for updating and stored on the storage device  34  of the server computer  4  to the further central computers  5   a ,  5   b , where, using the file(s) conveyed by the central computer  5 , the communication-control software stored on the corresponding storage device  8   a ,  8   b  is updated in a manner known per se.
The invention relates to a method for updating software that is stored in a computer of a data communication system, a computer to be used in a data communication system, and a data communication system comprising several computers and an administrative computer. Data indicating which transmission medium should be used for exchanging data that is used for updating or controlling the updating process is exchanged between one of the said computers and the administrative computer before software that is stored in said computer or in a storage device assigned thereto is updated.