Abstract:
The invention relates notably to a method for providing connectivity between hosts in a data communication network, at least one host, herein called semi-permanent user, being able to be connected to a Network Access Server over an access network.  
     According to the invention, the method comprising the steps of:  
     storing connection parameters of the semi-permanent user in a database accessible by the Network Access Server, said connection parameters identifying unambiguously said semi-permanent user in said access network;  
     scanning the occurrence of events directed to the semi-permanent user at an Event Management System when the semi-permanent user is not connected to the Network Access Server;  
     upon occurrence of one of these events, triggering the Network Access Server by the Event Management System to establish a connection to the semi-permanent user by using the connection parameters.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    The present invention relates to data communication networks and more particularly to communication with hosts connected to the core network over an access network.  
           [0002]    The framework of this invention concerns the way individuals and companies are given access to interconnected data communication networks. Interconnected data communication networks consist for example in the public Internet and in a plurality of virtual private networks (VPN) operated by third parties. These third party VPNs may be corporate intranets to which external access is severely controlled, for example, by firewalls. Access to such interconnected data communication networks is usually provided to individuals or small and medium enterprises by an access service provider owning a Network Access Server (NAS).  
           [0003]    [0003]FIG. 1 represents a network configuration for enabling individuals to access over an access network to interconnected data communication networks. End-users  111 ,  112  are connected over access networks  121  to Network Access Server  131 . Network Access Server  131  enables the access of end-users  111 ,  112  to the core network  14  and to the interconnected data communication networks  151 , . . . ,  152 . Some hosts  161 , . . . ,  162  belonging to the interconnected data communication networks  151 , . . . ,  152  are represented on the figure by way of example. These hosts may be server or users as end-users  111 ,  112 .  
           [0004]    Interconnected data communication network  151  may be associated to Network Access Server  131  and as a consequence play a privileged role for users  111 ,  112  in that Network Access Server  131  as well as data communication network  151  are owned by a single access service provider. Several value-added services, may be proposed by the access service provider to the end users, such are e-mail, web-browsing, web-page hosting and so on.  
           [0005]    Access network  121  may be usual telephone networks like PSTN (Public Switched Telephone Network) or ISDN (Integrated Services Digital Network). It may also be dedicated access networks as cable networks supporting ADSL (Asymmetric Digital Subscriber Line) as well as radio access networks like LMDS (Local Multipoint Distribution Services).  
           [0006]    If access networks  121  is usual telephone networks, Network Access Server  131  comprises analog modems to terminate PSTN analog connections. In case of an ISDN digital connection, the signal needs not to be demodulated. Network Access Server  131  also comprises a router function and a gateway to the core network  14 .  
           [0007]    The usual communication establishment protocol is described below. Host  111  establishes a connection to Network Access Server  131  over the access network  121 , Network Access Server  131  opens a session and assign an IP address to the user. Network Access Server  131  releases the session when user  111  closes the connection to Network Access Server  131 . As a consequence, when the connection to Network Access Server  131  is released, end-user  111  can no more be informed of events being destined to him. For example, end user  111  is no more alerted on incoming e-mails, or an attempt by another user to access a URL stored on the computer of end-user  111  will fail.  
           [0008]    An issue is that end-user  111  should keep connected to Network Access Server  131  to be alerted in real time of events destined to him. This proves to be expensive. Moreover, for analog users having usually only one telephone line available, the telephone line is busy during the connection to Network Access Server  131  and cannot be used for usual telephone calls for the duration of the connection.  
           [0009]    A solution to cope with this problem is available for ISDN users. In this feature called always-on-ISDN (AODI), the D-channel can be used to maintain a permanent contact between user  111  and Network Access Server  131  without busying the B-channels. The D channel is used as well for its usual signaling task as for the task of transferring user data. The D-channel can trigger the reservation of a B-channel when the amount of user data on the D-channel becomes to important. Usually an e-mail can be exclusively transported on the D-channel, if it does not contain a too large attachment.  
           [0010]    However, this solution is not adapted to all kinds of users connected to a Network Access Server for example to analog users or to ASDL users.  
           [0011]    The object of the present invention is to provide a method for enabling access from a data communication network to a host connectable to the data communication network over an access network but not always online.  
           [0012]    Another object of the invention is to provide a Network Access Server and an event management system to implement such a method.  
         SUMMARY OF THE INVENTION  
         [0013]    These objects, and others that appear below, are achieved by a method for providing connectivity between hosts in a data communication network, at least one of the hosts, herein called semi-permanent user, being able to be connected to a Network Access Server over an access network, the method comprising the steps of:  
           [0014]    storing connection parameters of the semi-permanent user in a database accessible by the Network Access Server, the connection parameters identifying unambiguously the semi-permanent user in the access network;  
           [0015]    scanning the occurrence of events directed to semi-permanent user at an Event Management System when semi-permanent user is not connected to Network Access Server;  
           [0016]    upon occurrence of one of the events, triggering Network Access Server by Event Management System to establish a connection to semipermanent user by using the connection parameters.  
           [0017]    These objects are further attained by a Network Access Server adapted for enabling hosts of an access network to access to a data communication network, the Network Access Server comprising a connection establishment module to be triggered by an Event Management System to initiate a connection establishment to a host of the access network, herein called semi-permanent user, by using connection parameters of said semi-permanent user stored in a database accessible by Network Access Server, the connection parameters identifying unambiguously semi-permanent user in the access network.  
           [0018]    These objects are also attained by an Event Management System to be associated to an Network Access Server, comprising:  
           [0019]    means for accessing to a database storing connection parameters of hosts of an access network, said connection parameters identifying unambiguously semi-permanent user in the access network;  
           [0020]    an event detection module for detecting the occurrence of events destined to a host of the access network registered in the database, herein called semi-permanent user;  
           [0021]    a trigger module for triggering Network Access Server and indicating said connection parameters of semi-permanent user.  
           [0022]    The method according to the present invention enables a Network Access Server to establish automatically a session toward an end-user when an event concerning this end user has been detected at the Network Access Server. This requires that the Network Access Server knows connection parameters unambiguously identifying the end-user.  
           [0023]    An advantage of this method is that it can be implemented independently of the type of access network supporting the connection of the end-user to the Network Access Server. It does not require a modification of the physical connection and can be completely implemented in a software form.  
           [0024]    Another advantage of the method according to the present invention is that the access network operator can avoid long lasting but idle connections and hence optimize the use of network resources.  
           [0025]    This invention can be used for enabling the access to a content located at the computer of the end-user and referenced as freely accessible in the network even if the computer is not permanently online.  
           [0026]    Further advantageous features of the invention are defined in the dependent claims.  
           [0027]    This invention is based on a priority application EP 00 44 011 7 which is hereby incorporated by reference. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0028]    Other characteristics and advantages of the invention will appear on reading the following description of a preferred implementation of the method given by way of non-limiting illustrations, and from the accompanying drawings, in which:  
         [0029]    [0029]FIG. 1 shows a network configuration for enabling individuals to access over an access network to interconnected data communication networks (prior art);  
         [0030]    [0030]FIG. 2 shows an embodiment of a network environment supporting a method according to the present invention;  
         [0031]    [0031]FIG. 3 shows messages exchanged between the different entities of the network environment shown on FIG. 2;  
         [0032]    [0032]FIG. 4 shows an embodiment of a Network Access Server according to the present invention;  
         [0033]    [0033]FIG. 5 shows an embodiment of a EMS according to the present invention. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0034]    [0034]FIG. 1 has already been described in relation with prior art.  
         [0035]    [0035]FIG. 2 shows an embodiment of a network environment supporting a method according to the present invention. The network environment comprises a first user  21 , a second user consisting in a web-server  22 , a data communication network  20 , Network Access Servers  201 ,  202 , an access network  203 , a domain name server  23  coupled with a database  24 , an event management system (EMS)  25  and an accounting system  26 .  
         [0036]    Calling user  21  is connected to data communication network  20  over Network Access Server  201 . However, this type of connection is not required by the present invention and could be any other type of connection, for example a leased line.  
         [0037]    Web server  22 , also called semi-permanent user, is able to be connected to data communication network  20  over access network  203  and Network Access Server  202 . Network Access Server  202  is located at the interface between access network  202  and data communication network  20 .  
         [0038]    For sake of simplicity calling user  21  and web server  22  are represented as belonging to the same data communication network  20 . However, it will be clear for those skilled in the art that this is not a requirement of the invention and that a network configuration comprising a plurality of interconnected data communication networks could also and even preferably be used in the framework of the present invention. In such a network configuration EMS  25 , accounting system  26  and semi-permanent user  22  would preferably be connected to the same data communication network.  
         [0039]    In this embodiment, semi-permanent user  22  is a web-server, hosting web pages addressed by means of URL (Universal Resource Locator). Web-server  22  is located in the so-called Customer Premises Domain that means that the contents of the web-server are physically stored at the user computer and not on a disk space at the access provider. Web server  22  is however not permanently connected to access network server  202  contrary to always-on scenario where a connection would be kept permanently alive between web server  22  and Network Access Server  202  by means of the D-channel in ISDN.  
         [0040]    It is the purpose of the present invention to guaranty connectivity between the web-server  22  and data communication network  20  on as-needed basis. Indeed, a connection between web server  22  and Network Access Server  202  will be established at the initiative of Network Access Server  202  only when a calling user  21  wants to access to the contents located at web server  22  and the attempt of calling user  21  is detected in Event Management System (EMS)  25 .  
         [0041]    This invention provides a solution to market segments which up to now had no adequate method for offering online services. An example for users of this service are doctors keeping medical records of patients stored on a server at his office and who give the patients the possibility to check their medical records. Since these checks would possibly be rare and have a short duration, a permanent connection between server  22  and Network Access Server  202  is not necessary and could perhaps be too much subject to hackers. Then, only when a patient willing to check his medical record is identified at EMS  25 , a connection between the server  22  and the access network  20  is established at the initiative of Network Access Server  202 .  
         [0042]    This special application is only given for sake of illustration. Any application requiring the establishment of a connection between a server located at in the Customer Premises Domain and a Network Access Server on an as-needed basis can be implemented by using the method according to the present invention.  
         [0043]    Other applications where semi-permanent user  22  is not a server but a usual computer may be envisaged. For example, home working could be simplified by the use of the method according to the present invention. Indeed, the user could be alerted that e-mails, incoming Voice over IP calls or instant messaging services have been identified at EMS  25  as destined to him when semi-permanent user  22  is not currently online. In this situation, semi-permanent user  22  would give the authorization to Network Access Server  202  to automatically establish a connection to him when special events predefined by semi-permanent user  22  himself are detected at EMS  25 , which per nature is permanently connected to the data communication network  20 .  
         [0044]    Web server  22  has to be registered at the Network Access Server  202  for benefiting from the service according to the present invention. This registration can be a permanent subscription or can be proposed automatically to the administrator of server  22  each time a previously established connection between web server  22  and Network Access Server  202  is released.  
         [0045]    Indeed, when web server  22  connects at his own initiative, he is automatically registered as being reachable at that place by the Network Access Server. Sufficient connections parameters are a telephone number in case of narrow band Network Access Server or a couple of VP/VC (Virtual Path/Virtual Channel) in case of broadband ATM (Asynchronous Transfer Mode) Network Access Server. When web server  22  closes the session, he indicates that he will remain reachable at this address for some time (e.g. for the rest of the day if he is working at home), and that he would like to be accessible for calling user selecting a URL located on web server  22 .  
         [0046]    For the purpose of registration, connection parameters of web server  22  must be stored in a database coupled to EMS  25 .  
         [0047]    An entry of this database contains mandatory parameters: the domain name or URL referencing the web pages located on server  22 , an identifier for identifying Network Access Server  202  which should be used for establishing the connection with web server  22 , and parameters necessary to establish this connection, e.g. telephone number of the telephone line through which the server is connected to the access network in case the access network is the PSTN or the ISDN or ATM VP/VC for connections via ATM/ADSL, etc . . . .  
         [0048]    These connection parameters are preferably stored when server  22  registers on Network Access Server  202 .  
         [0049]    Other optional parameters may be envisaged. Preferably, the type of events semi-permanent user  22  selects to trigger the automatic establishment of a connection at the initiative of Network Access Server  202  can also be stored in database. Examples for such events are, the reception of e-mails directed to semi-permanent user  22 , the reception of a Voice over IP call directed to semi-permanent user  22  at Network Access Server  202 , a connection attempt to an URL located on semi-permanent user  22 . More complex events can also be envisaged such as e-mail with a certain priority.  
         [0050]    The Network Access Server identifier is required as entry of the database when the database is shared among several Network Access Servers for example all belonging to the same access provider.  
         [0051]    Network Access Server  202  is extended with a new feature, such that it can take the initiative to startup a session to a server  22  located in the CPE domain, when this is requested by EMS  25 . This new features will be described in more details below.  
         [0052]    EMS  25  is a system that supervises the occurrence of events selected by the different semi-permanent users having subscribed to a service according to the present invention. A permanent software process is running to check if events are directed to one of the semi-permanent users registered in the database and if these events match the events mentioned by the corresponding semi-permanent user.  
         [0053]    Preferably, DNS  23  has additional intelligence to check if the domain name is associated with a semi-permanent user according to the present invention, and to indicate this to EMS  25 .  
         [0054]    [0054]FIG. 3 shows messages exchanged between the different entities of the network environment shown on FIG. 2.  
         [0055]    Steps  31  to  33  show the registration mechanism of semi permanent user at EMS  25 . At the occasion of a connection to Network Access Server  202  established at the initiative of semi-permanent user  22  (step  31 ), the latter connects to EMS  25  (step  32 ) where it lets store its connection parameters and the type of events he wants to have the method according to the invention applied to. Then semi-permanent user  22  release its connection to Network Access Server  202 .  
         [0056]    The followings steps show how the occurrence of an event destined to semi-permanent user  22  is treated.  
         [0057]    Step  34 : Calling user  21  connects to the access provider&#39;s network  20 . This connection mechanism is not part of the present invention. When the calling user  21  wants to connect to web server  22 , he enters a URL in his navigation programs. This URL contains the domain name associated to contents stored on web server  22 .  
         [0058]    This request is sent to the DNS server in the access provider&#39;s domain (2). A usual DNS server would return the IP address of the server. In the framework of the present invention, the server is not permanently connected to the network, the server may not have a permanent IP address registered in the domain name server.  
         [0059]    Step  35 : In this case, the DNS server  23  identifies this domain name as related to the new type of subscription, and forwards the request to the Event Management System  25 . EMS  25  controls the rest of the scenario.  
         [0060]    Step  36 : EMS  25  checks if the connection to web server  22  is already online. If not, it retrieves the necessary connectivity parameters from the database, and sends a message to Network Access Server  202  to establish the connection.  
         [0061]    Step  37 : Network Access Server  202  establishes on his own initiative the connection to web server  22 , including the allocation of an IP address to web server  22  (typically via PPP).  
         [0062]    Step  38 : Network Access Server  202  returns the allocated IP address to EMS  25  which forwards the IP address to DNS  23 . Finally, the DNS returns the IP address to calling user  21 .  
         [0063]    Step  39 : the connection between calling user  21  and web server  22  is established.  
         [0064]    In a preferred embodiment, calling user  21  is billed for this call to web server  22 . Calling user is connected to accounting system  26  and asked to enter authentication information. This authentication information could for instance be a calling card number and PIN code in case the accounting system is a calling card system. This authentication step can be advantageously performed between step  35  and step  36 . If this authentication step is successful, the method according to the present invention is resumed.  
         [0065]    Preferably, EMS  25  activates a “watchdog” in Network Access Server  201 , to monitor when calling user  21  disconnects from the web server  22 . EMS  25  keeps track of the different watchdogs associated with calling users who may simultaneously be connected to web server  22 .  
         [0066]    This watchdog in Network Access Server  201  is used to control the call termination as follows:  
         [0067]    If calling user  21  terminates his session, the watchdog sends a trigger to EMS  25 . EMS  25  stops the accounting for this particular session. Then, it checks if any other users still have a connection to web server  22  open. If not, EMS  25  triggers Network Access Server  202  to terminate the connection with web server  22 .  
         [0068]    Optionally, if calling user  21  remains connected to Network Access Server  201 , but starts browsing to a different URL, the watchdog system in Network Access Server  201  can send to the calling user  21  a notification to ask him if he wants to terminate the connection to web server  22 . If so, the watchdog will start the call termination process as before.  
         [0069]    If the user chooses to keep the session open, the watchdog may start alternative mechanisms to control session termination (e.g. regularly send a notification to calling user  21  that the session is still open; or download a Java applet to the user terminal through which the user can stop the session at all times, a.s.o . . . )  
         [0070]    If new calling users want to connect to web server  22  while the connection to Network Access Server  202  is already open, the scenario is similar as the one described above, except that the EMS  25  can immediately return the IP address of the server to the further calling users.  
         [0071]    [0071]FIG. 4 shows an implementation of a Network Access Server according to the present invention. The Network Access Server  40  comprises three interfaces : interface  401  to an Event Management System, interface  402  to a data communication network and interface  403  to an access network. Network Access Server  40  comprises an usual Network Access Server module  41  connected to interface  402  and  403  supporting the usual functionality of a Network Access Sever (for example the modems pool, the IP addresses allocation module) and a connection establishment module  42  connected to interface  401  and to usual Network Access Server module  41 .  
         [0072]    Connection establishment module  42  receives over interface  401  a connection establishment message from an Event management System when the latter has detected an event requiring a connection to be initiated at the initiative of the Network Access Server. The connection establishment message contains connection parameters of a semi permanent user so that the Network Access Server can uniquely identify the semi-permanent user. Furthermore the message can optionally contain an information concerning the type of event that have triggered this automatic connection establishment at the initiative of the Network Access Server.  
         [0073]    Upon reception of the connection establishment message, Connection establishment  42  triggers usual Network Access Server module  41  by sending him a message identical to the message usual Network Access Server module  41  would receive from a user requiring a connection to be established. As a consequence, connection establishment module  42  emulates a connection request issued by a calling user. This is possible since all semi-permanent user parameters are available at connection establishment module  42 . Then, usual Network Access Server module  41  performs the usual connection establishment steps comprising for example the allocation of an IP address to the semi-permanent user, and the reservation of a modem out of the modem pool if the semi-permanent user is an analog user.  
         [0074]    Upon successful establishment of the connection at the initiative of the Network Access Server, usual Network Access Server module  41  returns a message to connection establishment module  42  containing parameters associated to the currently established connection (e.g. IP address). Connection establishment module  42  returns this information to the Event Management Server. After the connection establishment, the session continues as if it were a normal session.  
         [0075]    Preferably, connection establishment module  42  takes also care that accounting will not be billed to the semi-permanent user, since the calling user will already be billed for the connection. For this purpose, the connection establishment message issued by the connection establishment module should contain a field indicating that the connection at the initiative of the Network access server should not be billed to semi-permanent user.  
         [0076]    The establishment procedure is preferably supported by the commonly used access protocol PPP (Point to Point Protocol). Other access protocols supporting unsolicited messages from the network side to the terminal side could be used.  
         [0077]    Protocol such as DHCP not supporting unsolicited messages can also be used under the condition that the access network operator installs a client side application on the semi-permanent user terminal dealing with unsolicited messages. This proprietary solution can be used to realize the session setup.  
         [0078]    [0078]FIG. 5 shows an implementation of an Event Management System according to the present invention. Event Management System  50  comprises a database  51 , an event detection module  52 , a trigger module  53 , an interface  501  to a data communication network, and an interface  502  to a Network Access Server.  
         [0079]    Event detection module  52  is connected to interface  501  and to triggering module  53 . Event detection module  52  preferably supports a permanent running software process that listens to specific events destined to semi-permanent users registered in database  51 . Alternatively, event detection module  52  could subscribe to external systems e.g. Mail system or DNS so that these external systems alert event detection module when a particular event occurs. This could be implied thanks to a communication protocol or an API between event detection module and external systems.  
         [0080]    When such an event is identified, triggering module  53  transmit over interface  502  to the Network Access Server a message containing the connection parameters of the concerned semi-permanent user.  
         [0081]    It is the task of the Network Access Server to take care of establishing the session (e.g. via PPP). Once the session is established, i.e. the user terminal has connectivity to the whole network, the EMS can send the correct notification to the user (e.g. indicating that there are  20  new emails in his mailbox).