Abstract:
To construct directories automatically in a group of terminals of a local area network, a given terminal that has just been connected broadcasts a message containing its name and address. Another terminal of the group decodes the broadcast message, extracts the name and address of the given terminal from the broadcast message in order to insert them in a directory, and transmits its name and its address in a response message containing the address of the given terminal. The given terminal decodes the response message, extracts the name and the address of the other terminal from the response message, and inserts them in a directory.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    The present invention relates generally to digital terminals, in particular telephone terminals, interconnected via a local area network LAN. The invention relates more particularly to the automatic construction of directories of called parties in the terminals when a new terminal is connected to the network or when one of the terminals changes its address.  
           [0003]    2. Description of the Prior Art  
           [0004]    In a local area network supporting the Transport Control Protocol/Internet Protocol TCP/IP at the level of the network and transport layers, i.e. in intranet networks, each terminal is associated with an IP address including, for example, a series of four bytes, for example 143.14.18.178, and where appropriate a network name which is not very evocative of the terminal, for example PC63B912. As terminal users are not accustomed to using designations of this kind, which are the preserve of data processing specialists, it has proved necessary to construct a directory manually in each terminal to contain the usual names of the other terminals of the network so that they can be addressed easily, such usual names being printer X, station Y, fax  3 , etc, for example. Thus in each terminal a translator function associated with its directory maps the usual name of each terminal that can be called to the IP address or the network name of the terminal.  
           [0005]    As is well known in the art, when a given terminal is to be added to a local area network, it is necessary not only to write all the other terminals of the network into the directory of the given terminal, which is fastidious in itself, but also to update the directories of all the terminals of the network to include the given terminal, which is also fastidious. If the network contains several dozen or hundred terminals, loading the addresses and names into the terminals when a given terminal is installed represents several hours of work.  
         OBJECT OF THE INVENTION  
         [0006]    The main object of this invention aims to remedy the drawbacks referred to above by automatically constructing the directory of the new terminal connected to a network and automatically updating the directories of the other terminals of the network, which has the advantage of avoiding the need to use the services of a data processing specialist to list a new terminal in a local area network.  
         SUMMARY OF THE INVENTION  
         [0007]    Accordingly, a method of constructing directories in terminals connected by a local area network, the method includes the following steps:  
           [0008]    broadcasting a message from a given terminal in the network, the broadcast message containing at least a name and an address of the given terminal,  
           [0009]    in at least one other terminal, decoding the broadcast message, extracting from it the name and the address of the given terminal, inserting the extracted name and address in mapping relationship into a directory of the other terminal, and transmitting a response message containing the address of the given terminal as a receiver address and at least the name and the address of the other terminal extracted from the broadcast message, and  
           [0010]    decoding the response message in the given terminal, extracting the name and the address of the other terminal from it, and inserting the extracted name and address in mapping relationship into a directory of the given terminal.  
           [0011]    When the network comprises plural types of terminals, for example fax and computers, the given terminal and plural other terminals in the network define a group of terminals associated with an identifier. The broadcast message includes then preferably said identifier so that only said plural other terminals decode the broadcast message to extract from it the name and the address of the given terminal.  
           [0012]    The broadcast message and the response message can each include a directory construction function field.  
           [0013]    The address contained in the broadcast message or the response message can include a sender terminal address conforming to the internet protocol and/or an electronic mail address of the sender terminal.  
           [0014]    The broadcasting step follows on automatically from the given terminal being connected to the network which can be preceded by a first installation of the given terminal in the network or by disconnecting (powering down) the given terminal. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0015]    Other features and advantages of the present invention will become more clearly apparent after reading the following description of preferred embodiments of the invention, which description is given with reference to the corresponding accompanying drawings, in which:  
         [0016]    [0016]FIG. 1 is a block diagram of a local area network including a few terminals;  
         [0017]    [0017]FIG. 2 shows the structure of a level identification packet at the IP protocol according to the invention; and  
         [0018]    [0018]FIG. 3 is an algorithm of the steps of a method of constructing directories in the terminals of the FIG. 1 local area network. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0019]    This example refers to a CSMA/CD (Carrier Sense Multiple Access/Collision Detect) local area network whose topology is based on a bus BU. In FIG. 1, the network comprises N terminals T 1  to T N  connected to the bus BU. In this kind of network a terminal can send a frame if it does not detect any frame on the bus BU. The preferred embodiment referred to hereinafter relates to an Ethernet network in which the frames encapsulate IP packets conforming to the TCP/IP protocols. FIG. 1 does not show other machines that may be connected to the bus BU, for example a gateway between the local area network and the public switched telephone network constituting a PABX type private data processing platform.  
         [0020]    [0020]FIG. 2 shows the general structure of an IP packet with a standard header EN and a data field CD. The header includes the address of the sender of the packet if the packet is broadcast or that address and a receiver address and at least the address of the source port and the address of the destination port in relation with the directory application in a terminal at the TCP transport layer level.  
         [0021]    According to the invention, the data field CD includes an identification field IF, a function field FN and parameter fields PA. The identification field IF contains several characters that identify a group of terminals; for example, the group of terminals T 1 , T 2  and T n , with 1≦n≦N, referred to hereinafter, selected from the set of all the terminals T 1  to T N  Of the network, contains the same “fax” identifier so that the data field CD of a packet containing an identifier of that kind is processed only by the terminals T 1 , T 2  and T n . The function field FN containing a few bits indicates a function to be implemented in the terminal receiving the IP packet, for example a directory update function.  
         [0022]    Each parameter field PA is made up of three sub-fields TY, LG and DO. The fields TY and LG respectively specify the data type and the length of the data contained in the sub-field DO. For example, three parameter fields PA 1 , PA 2  and PA 3  are included in the data field CD of the IP packet. The parameter in the field PA 1  relates to the IP address of the terminal sending the IP packet, for example “124.1.2.3.”, contained in the sub-field DO 1 , having a length of ten characters, as indicated in the sub-field LG 1 , and corresponding to the type TY 1 =1. The parameter in the field PA 2  relates to the electronic mail (e-mail) address of the sending terminal contained in the sub-field DO 2 , for example “Toto.Sagem.com”, having a length of fourteen characters, as indicated in the sub-field LG 2 , and corresponding to the type TY 2 =2. The parameter in the field FA 3  relates to the network name, or preferably the usual name, of the sending terminal contained in the sub-field DO 3 , for example “Fax Toto”, having a length of sixteen characters, as indicated in the sub-field LG 3 , and corresponding to a third type indicated in the sub-field TY 3 =3.  
         [0023]    As explained hereinafter, this kind of a packet IP n  is broadcast by the terminal T n  in particular when it is installed in the network and the packets IP 1  and IP 2  of this kind are respectively transmitted in response from the terminals T 1  and T 2  to the terminal T n . The packet IP n  is a broadcast packet which is addressed only to the other terminals T 1 , T 2  of the same group, which are characterized by an identifier IF common to the terminals T 1 , T 2  and T n , while the packets IP 1  and IP 2  are intended only for the terminal T n  and consequently contain its address as the receiver address.  
         [0024]    The construction of directories in the terminals T 1 , T 2  and T n  shown in FIG. 3 is triggered by one of two events signaled in steps E 1  and E 2 .  
         [0025]    In step E 1 , the terminal T n  is inserted into the network by installing it and then connecting it to the bus BU. The content of the fields IF, FN and PA 1  to PA 3  relating to the terminal T n , as the sender terminal, can be determined at least in part by the terminal manufacturer and/or at least in part by the terminal user.  
         [0026]    For step E 2 , it is assumed that one of the parameters PA 1  to PA 3  relating to the terminal T n  already installed has been modified at the time of a connection to the network. For example, the network includes a server containing the DHCP (Dynamic Host Configuration Protocol) for dynamically attributing IP addresses to the terminals T 1  to T N  Of the network, or more generally for dynamically allocating at least one of the parameters PA 1  to PA 3  relating to the terminal T n  when the latter is connected to the network for the first time, as in step E 1 , or more generally when it is connected to the network each time it is powered up. The server therefore configures the terminal T n  automatically in step E 2  by dynamically allocating it an IP address.  
         [0027]    After step E 1  or E 2 , the method of constructing directories includes the successive main steps E 3  to E 11 , of which steps E 3  and E 8  to E 11  are executed in the calling terminal Tn and steps E 4  to E 7  and E 11  are executed in each of the called terminals T 1  and T 2 .  
         [0028]    After step E 1  or E 2 , following connection of the terminal T n  to the network bus BU, the terminal T n  broadcasts on the bus BU the packet IP n  containing in particular parameters PA 1 , PA 2  and PA 3  which are specific to the step E 3 . In particular, the packet IP n  contains the identifier IF common to all the terminals T 1 , T 2  and T n  Of the “fax” group in the network.  
         [0029]    All the terminals in the network reject the packet IP n  except for the terminals T 1  and T 2 , which recognize the identifier IF specific to their group. Each terminal T 1  T 2  then executes steps E 4  to E 7 .  
         [0030]    In step E 4  the packet IP n  is decoded in the receiver of the terminal T 1 , T 2 , which recognizes the group identifier IF. At the level of the application service designated by the destination port in the field FN of the packet IP n  and relating to updating of directories, in step E 5  the terminal T 1 , T 2  extracts the parameter fields PA 1  to PA 3  from the packet IP n . The directory in the terminals T 1 , T 2  is then updated (step E 6 ), in particular by entering as a new usual name the name of the terminal T n  contained in the sub-field DO 3  extracted from the packet IP n  and the parameters in the other sub-fields DO 1  and DO 2  extracted from the packet IP n  enabling the terminal T n  to be called from the terminal T 1 , T 2 . If, in harmony with step E 2 , terminal T n  is already listed in the directory in the terminal T 1 , T 2 , the parameter(s) contained in the data field of the packet IP n  respectively replace the parameter(s) already stored in the directory of the terminal T 1 , T 2 .  
         [0031]    After this updating of the directory, the terminal T 1 , T 2  transmit a packet IP 1 , IP 2  conventionally containing their address as the sender address, the address of the terminal T n  as the receiver address, by means of the address IP contained in the sub-field DO 1  of the packet IP n  that has just been received, and parameters PA 1  to PA 3  enabling the terminal T n  subsequently to call the terminals T 1 , T 2  (step E 7 ).  
         [0032]    The terminal T n  executes steps E 8 , E 9  and E 10 , which are respectively analogous to steps E 4 , E 5  and E 6 , in response to each packet IP 1 , IP 2 . Because this packet contains the address of the terminal T n  , the packet IP 1 , IP 2  is recognized only by the terminal T n  and the directory updating application service is activated after the group identifier detected in the field IF and the corresponding function detected in the field FN of the packet IP 1 , IP 2 , respectively (step E 8 ). The parameters PA 1 , PA 2 , and PA 3  are extracted from the packet IP 1 , IP 2  thereby constructing the directory in the terminal T n  , by mapping the name of the terminal T 1 , T 2  in the sub-field DO 3  of the packet IP 1 , IP 2  to the address IP and the electronic mail address contained in the sub-fields DO 1  and DO 2  of the packet IP 1 , IP 2  (step E 10 ). The directory in the terminal T n  is therefore constructed automatically in response to all of the packets IP 1 , IP 2  from the terminals T 1 , T 2  in the group to which the terminal T n  belongs.  
         [0033]    After step E 7  in each called terminal T 1 , T 2 , or after step E 10  in the initially calling terminal T n  , the method of constructing directories is iterated (step E 11 ) if any of the terminals of the group in question, which has now become the terminal T n , is disconnected from the network, i.e. is stopped, and then restarted (step E 2 ).  
         [0034]    Accordingly, a user taking place in front of the terminal T n  can send a message, for example a fax message, directly to one of the terminals T 1 , T 2  of the group using the local directory in the terminal T n  that has just been constructed automatically, without any intervention on this directory by the user. Similarly, after the terminal T n  is installed or has been connected, a user taking place in front of the terminal T 1 , T 2  can transmit a message, for example a fax message, directly to the terminal T n  using the local directory included in the terminal T 1 , T 2  that has just been updated automatically, without any intervention on this directory.  
         [0035]    The invention is not limited to an Ethernet local area network (LAN) as described above, and can be applied to any form of local area network, regardless of its size, and therefore to any local area network LAN that can be installed in a private home or in a company, or any metropolitan area network (MAN) installed in a building or in several buildings of a business, and can be applied to any local area network regardless of its architecture and its technology and therefore to any single-bus or double-bus, star-connected, cable, ring or optical fiber network, or wireless WLAN or high-performance radio LAN (HiperLAN).