System and method for session reestablishment between client terminal and server

0001The present invention relates to a system and a method for establishing a session between a client terminal and a server, and more particularly to a system and a method for reestablishing a session for a messenger service between a client terminal and a server.

0002During communication with a server, a client terminal may be abruptly disconnected due to a normal or an abnormal off, such as log-off or timeout. In such an event, it is necessary to reestablish a session between the client terminal and the server.

0003<figref idref="f0001">FIG. 1</figref> is a view illustrating the structure of a conventional system for communication between a client terminal and a server.

0004In <figref idref="f0001">FIG. 1</figref>, reference numeral 10 refers to client terminals. As shown in <figref idref="f0001">FIG. 1</figref>, a personal computer 100 connected to a server 110 through an Internet network 108, as well as a mobile phone 102 and a PDA (Personal Data Assistant) 104 connected to the server 110 through a wireless mobile communication network 106, can be client terminals. All other terminals capable of receiving a messenger service are also included within the scope of client terminals.

0005When any client terminal 10 sends a request for login, the server 110 determines whether the client terminal 10 is an effective user and, if it is an effective user, sends a reply with a new session ID to the client terminal 10. Subsequently, the client terminal 10 receives a friend list (or a contact list) and presence information about the listed friends (i.e., other users) from the server 110. The presence information includes the status (e.g., online or offline), addresses, and other contact data, such as telephone numbers, of the listed friends.

0006Messenger services offered to the users through client terminals vary according to the messenger service providers. Such services include a Yahoo messenger service.

0007The server 110 connected to the client terminals 10 through the Internet network, provides a messenger service upon a demand from the client terminal10. The server 110 has a user information database that includes a friend list of each client terminal user, online or offline status (of the listed friends) and, address and other contact data of each listed friend (e.g., a telephone number of each listed friend).

0008<figref idref="f0002">FIG. 2</figref> is a flow diagram showing a conventional process of session establishment between a client terminal and a server.

0009When a user inputs a demand for messenger service, the user's client terminal 10 sends a request for login to the server 110 at step 204. Upon receiving the login request, the server 110 checks whether the client terminal 10 is an effective user and sends a new session ID to the client terminal 10. The client terminal 10 and the server 110 perform a service negotiation and a capability negotiation to send or receive information necessary to log in, such as a service to be used and the capability of the client terminal 10 at step 205. The client terminal 10 then sends a request for presence information to the server 110 in step 206. Then the client terminal 10 receives a friend list and presence information of the listed friends (other users) from the server 110 in step 208. The presence information includes the online or offline status, addresses, and other contact data, such as telephone numbers, of the listed friends.

0010However, during the session establishment, unnecessary data may be transmitted, thereby increasing traffic and consequently, consuming time. Accordingly, there is a need for an improvement of the conventional session establishment system and method.

0011It is assumed that the communication between the server 110 and a user's client terminal 10 was terminated normally or abnormally at 3:00 p.m. and that the client terminal 10 tries to access the server 110 again at 4:00 p.m. Since one hour lapsed after termination of the previous access, the session information (including the type of service offered to the user, capability of the client terminal, presence information of other users in the friend list and exchanged messages) possessed by the client terminal 10 one hour earlier may have been changed. Therefore, the client terminal 10 checks all relevant data received from the server 110 to confirm whether the session information is still effective. Even unchanged data is checked at this time. In other words, if the session information stored in a session information database 112 at 3:00 p.m. has not been changed until 4:00 p.m., the client terminal 10 will request all session information again at 4:00 p.m. Also, the server 110 will send all the previous session information which was provided an hour earlier in response to the request of the client terminal 10. This procedure is inefficient in terms of data traffic and time.

0012Since the client terminal 10 does not store session information when terminating its access to the server 110, it has to receive all the data of the previous session information from the server 110 when reaccessing the server 110. Even if the session information available at the next access is identical to that used at the previous access or has few updated items, the client terminal 10 receives all relevant data from the server 110, which causes unnecessary data traffic and consumes time. <patcit id="pcit0001" dnum="EP1303102A"><text>EP-A-1 303 102</text></patcit> relates to a user-centric session management for client-server interaction using multiple applications and devices. The server in this context is a provisioning server that provides objects, i.e. content and applications, to requesting clients. Clients are arbitrary devices with network access and applications that enable them to interact with the provisioning server. The objects themselves can also be of any of various types such as ringtones, Java applications, media files or text messages. Each user has an unique user identification (UI), and each session has a unique session identifier (USI). The system includes a session manager that accesses a session state memory and a virtual device memory. The session state memory provides short term storage of records of all current client server sessions, including USI and associated Uls. The UI is used to reconnect to an ongoing session primarily when the user changes client devices, and thus, the USI is not readily available, or if the client device does not support the USI. A connect request results in either a new session object with a new USI that is stored in session state memory, or in a reconnect to an existing session object in the session state memory. Anytime an action leads to a change in client device state, that change is first reflected in the virtual device memory in the provisioning server. The state changes are initially stored as unsynchronized changes, waiting for downloads to be confirmed by the client. If there are unsynchronized changes in the virtual device memory for the UI of the user, the session manager determines whether the current client device that the user is using is capable of downloading the changes. If so, the session manager prompts the client device to complete the download of the unsynchronized changes, the session resumes. If not, synchronization is postponed until the user reconnects again with a client device capable of accepting the unsynchronized changes. <nplcit id="ncit0001" npl-type="b"><text>Parviainen, R., et al, "Mobile Instant Messaging", Telecommunications 2003, ICT 2003, 10th International Conference, Piscataway, NJ, USA, IEEE, February 23, 2003, pages 425 to 430</text></nplcit>, relates to mobile instant messaging. A mobile instant messaging system, MIM, designed for mobile environments is described. If a network connectivity is lost or the user switches connection method, the user is marked as being "offline", although there might be a high probability that the connectivity is regained shortly. In a wireless network, this will be problematic since short losses of connectivity might occur often when a user, for instance, is moved from one server to another or briefly looses coverage. Since current systems assume that the user's position is fixed to one PC, there is no location or position information. This is not the case for a mobile device, here a user's position dynamically changes and can provide important and variable information to other contacts. A user should be able to move from his home PC to a mobile unit such as a phone while on the road and finally to his work PC without having to remember to manually log out from each unit before switching to a new one the user status should not switch from "online" to "offline" and back again each time the user switched units or when the network connectivity is temporarily lost since the user will probably regain connectivity shortly. The contact list should be automatically synchronized among the clients. <nplcit id="ncit0002" npl-type="b"><text>Campbell, J., Rosenberg, R., et al "Instant message sessions in simple draft-ieft-simple message-sessions-00", IETF standard working draft, Internet Engineering Taskforce, IETF, CH, vol. Simple, May 22, 2003</text></nplcit>, relates to instant message sessions in SIMPLE draft-ietf-simple-message-sessions-OO. It is described to the use of MSRP (message session relay protocol) between endpoints or via one or two relays, where endpoints have advance knowledge of the relays. Further, it describes the use of MSRP over TCP. MSRP may be used over other congestion-controlled protocols such as SCTP. The simplest use case for MSRP is a session that goes directly between endpoints, with no intermediaries involved. Assuming A is an endpoint that wishes to establish a message session, and B is the endpoint invited by A. A invited B to participate in a message session by sending B a URL that represents the session. This URL is temporary and must not duplicate the URL used for any other active sessions. The state associated with the session will expire over time, based on an expiration time specified in a VISIT request. If the lifetime of the session is to exceed that expiration time, the visitor must update that expiration with the new VISIT request prior to expiration.

0013Accordingly, the present invention has been made to solve the above-mentioned problems occurring in the prior art.

0014It is the object of the present invention to provide a system and a method for performing a session reestablishment which efficiently uses time and controls traffic flow by enabling a server to send only updated data in session information which had been provided during previous access when a client terminal reaccesses the server.

0015This object is solved by the subject matter of the independent claims.

0016Preferred embodiments are defined in the dependent claims.

0017In order to accomplish the above object of the present invention, there is provided a session reestablishment system including a client terminal capable of accessing a communication network, a session information database, and a server for providing a messenger service to the client terminal, wherein said client terminal sends a synckey exchanged and stored during previous access to the server when sending a request for session reestablishment (reaccess) to the server after lapse of a predetermined time period from termination of the previous access due to log-off or timeout; and wherein said server searches the session information database to detect last session information corresponding to the client terminal based on the synckey, compares the last session information with current session information to detect any updated data, and sends only the updated data to the client terminal.

0018In accordance with another aspect of the present invention, there is provided a method for session reestablishment in a system including a client terminal and a server for providing a messenger service to the client terminal, said method including: a client terminal sending a request for session reestablishment (reaccess) including a synckey to a server in order to receive a messenger service; the server's receiving the request for session reestablishment and comparing last session information stored right before termination of the previous access with current session information to detect any updated data; the server's sending the detected updated data to the client terminal; and the client terminal's receiving the updated data and updating the session information (or corresponding data in the session information) stored right before termination of the previous access.

0019The above object and other aspects, features and advantages of the present invention will be more apparent from the following detailed description taken in conjunction with the accompanying drawings, in which: <ul id="ul0001" list-style="none" compact="compact"><li><figref idref="f0001">FIG. 1</figref> is a view showing the structure of a conventional system for communication between a client terminal and a server;</li><li><figref idref="f0002">FIG. 2</figref> is a flow diagram showing a conventional process of session reestablishment between a client terminal and a server;</li><li><figref idref="f0003">FIG. 3</figref> is a view showing the structure of a system for communication between a client terminal and a server according to the present invention;</li><li><figref idref="f0004">FIG. 4</figref> is a flow diagram showing a process of session reestablishment between a client terminal and a server according to the present invention;</li><li><figref idref="f0005">FIG. 5</figref> is a flow chart illustrating operations performed by a client terminal for the session reestablishment according to the present invention; and</li><li><figref idref="f0006">FIG. 6</figref> is a flow chart illustrating operations performed by a server for the session reestablishment according to the present invention.</li></ul>

0020Hereinafter, a preferred embodiment of the present invention will be described with reference to the accompanying drawings. In the drawings, the same element, although depicted in different drawings, will be designated by the same reference numeral or character. Although certain features (such as various data forming presence information) are specifically defined in the following description of the present invention, it will be obvious to those skilled in the art that such definitions of elements are merely to improve understanding of the present invention and that the present invention can be carried out without such specific features. In addition, in the following description of the present invention, a detailed description of known functions and configurations incorporated herein will be omitted when it may make the subject matter of the present invention unclear.

0021According to the present invention, a client terminal requests a session reestablishment using the same synckey as used during previous access to a server.

0022<figref idref="f0003">FIG. 3</figref> shows the structure of a system for communication between a client terminal and a server according to the present invention.

0023As compared with the conventional system in <figref idref="f0001">FIG. 1</figref>, the system illustrated in <figref idref="f0003">FIG. 3</figref> further includes a user information database 115 for storing each user's previous session information. The previous session information refers to all previous information relating to a session, such as service types offered upon negotiation and agreement between the server and each client terminal, capability of the client terminal, presence attribute values, and instant messages. Presence attributes indicate the address, status, telephone number, etc. of each user (for example, <i>Gil-Dong Hong</i> in the friend list). The presence attribute values are detailed information (for example, address of <i>110-2, Myeongryun-dong 4-ga, Jongro-gu, Seoul, online</i> status and telephone number of <i>760-4930</i>). However, for explanatory convenience, the presence attributes and the presence attribute values are commonly termed "presence information" herein.

0024<figref idref="f0004">FIG. 4</figref> is a flow diagram showing a process of session reestablishment between a client terminal and a server according to the present invention.

0025It is assumed that the client terminal 10 has accessed the server 110 to share session information, including a user's friend list and data (e.g., presence information) on the status of the listed friends, and has then terminated the access.

0026During access to the server 110, the client terminal 10 and the server 110 exchange and share a session ID and a client ID. When the access is terminated, both the client terminal 10 and the server 110 store an ID for the last successful transaction (i.e., a transaction ID). The last successful transaction means a transaction conducted right before normal termination by logout or connection termination or before abnormal termination due to a connection failure. The session information includes service types used, capability of the client terminal, presence information of the users in the friend list, and exchanged messages.

0027When the access to the server 110 is terminated, the client terminal 10 stores the latest session information used in the last successful communication with the server 110. Also, the client terminal 10 stores a synckey relating to the session information. The synckey includes a session ID of the previous connection (session) between the client terminal 10 and the server 110, a client ID of the client terminal 10 that stores the friend list and the status of each friend, and a transaction ID of the communication between the client terminal 10 and the server 110. The session ID is provided from the server 110 to the client terminal 10. The client ID is provided from the client terminal 10. The transaction ID is provided by both the client terminal 10 and the server 110. The synckey including the three IDs has already been exchanged in the previous access and is known to the server and the client terminal.

0028Referring to <figref idref="f0004">FIG. 4</figref>, when a certain predetermined time has elapsed after the termination of a previous access to the server 110, the client terminal 10 may send a request for session reestablishment (reaccess) to the server 110 using the synckey including the old session ID, in step 300. In other words, the request for session reestablishment includes the synckey.

0029Upon receiving the request, the server 110 identifies the client terminal 10 and detects the synckey included in the request. Also, the server 110 confirms whether the same synckey is present in the user information database 115 that stores the user's previous session information in step 310. If the same synckey is detected, the server 10 will compare the last session state and the current session state to detect any updated data of session information in step 314. The updated data are, for example, messages newly received or a changed status of the friend list during disconnection.

0030The server 110 sends a reply for session establishment, including the session ID that was sent to the client terminal 10 at step 300, to the client terminal 10 in step 316. Then, the server 110 sends the updated data to the client terminal 10 in step 317. Moreover, steps 316 and 317 can be performed sequentially or concurrently. Based on the updated data, the client terminal 10 updates the previously stored session information. The above example illustrates a process of session reestablishment when there is updated data. If there is no updated data, the server 110 will only send a reply with the old session ID as included in the synckey to the client terminal 10 at step 316.

0031The synckey included in the request received from a client terminal 10 is compared with the synckey stored in the user information database. If the same synckey (as received from the client terminal 10) is not detected, the server 110 will send a reply for session establishment, including a new session ID, to the client terminal 10 in step 312. This reply, as a session reestablishment failure message, is identical to the reply sent when session reestablishment is successful, with a difference being that it includes a new session ID and data.

0032<figref idref="f0005">FIG 5</figref> is a flow chart showing operations performed by a client terminal for the session reestablishment according to the present invention.

0033The client terminal 10 is in a standby mode at step 400. The client terminal then proceeds to step 402 where it checks whether the user has inputted a demand for access to the server 110 to receive a messenger service. If there is no input, the client terminal 10 returns to a standby mode in step 400.

0034If a demand for access is inputted, the client terminal 10 proceeds to step 403 where it determines whether there is a stored synckey. If no synckey is detected, the client terminal 10 sends a request for general access to the server 110 in step 422. In other words, if the client terminal 10 does not store any previous (old) session information, it will send a request for login without including a synckey. After a service/client capability negotiation at step 423, the client terminal 10 sends a request for presence information to the server 110 at step 424. The client terminal 10 then receives current values from the server 110 to complete login. Step 403 and subsequent steps 422 to 424 are generally known in the art. An additional step of receiving user information or requesting a contact list can be performed between steps 423 and 424 and is known in the art, and therefore will not be shown or further explained herein. The contact list refers to a list of the user's contact groups, such as friends, family and colleagues. In the preferred embodiment of the present invention, a friend list is as an example of a contact list.

0035Steps 410 and 423 are performed when the server 110 sends a new session ID to the client terminal 10. The client terminal 10 compares the new session ID with the old (existing) session ID at steps 410. If the new session ID is not identical to the old one, the client terminal will proceed with step 423.

0036If a stored synckey is detected at step 403, the client terminal 10 will proceed with step 404 to send a request for session reestablishment (reaccess), including the detected synckey (including the old session ID), to the server 110. The presence of a stored synckey means that a session was previously established between the client terminal and the server.

0037At step 406, the client terminal 10 checks whether a reply to the request for reaccess is received from the server 110. If a reply is received, the client terminal 10 will proceed with step 408 to detect a synckey, preferably a session ID included in the synckey, from the reply. At step 410, the client terminal 10 determines whether the received session ID is identical to the (old) session ID which was sent to the server 110 at step 404. If the session IDs are identical to each other, the client terminal 10 will check whether any updated data is received from the server 110 at step 418. If updated data is received, the client terminal 10 will proceed with step 420 to update the session information based on the updated data.

0038<figref idref="f0006">FIG. 6</figref> is a flow chart showing operations performed by the server for the session reestablishment according to the present invention.

0039The server 110 in the standby mode at step 500 proceeds to step 502 where it checks whether a request for login has been received from the client terminal 10. If the request for login is received, the server 110 will proceed to step 504 where it determines whether or not there is a stored synckey. If a stored synckey is detected, the server 110 proceeds to step 514 where it determines whether the stored synckey is identical to the synckey that was received from the client terminal 10 (which includes the old session ID). The received synckey was included in the login request sent by the client terminal 10 at step 404 in <figref idref="f0004">FIG. 4</figref>. The presence of a stored synckey means that a session was previously established between the client terminal 10 and the server 110.

0040If no synckey is detected at step 504 or if no synckey is determined to be identical to the received synckey at step 514, the server 110 proceeds to step 522 where it sends a new session ID to the client terminal 10. If an identical synckey is detected, the server 110 will send the session ID included in the received synckey to the client terminal 10 in response to the login request and will proceed with step 516. At step 516, the server 110 searches for the last session information from the user database 115 that stores previous session information of each session information user. The server 110 compares the last session information with the current session information to detect any updated data. At step 518, the server 110 sends a reply including the old session ID (the client terminal 10 receives the reply at step 406 in the process shown in <figref idref="f0005">FIG. 5</figref>). The server 110 then sends the updated data to the client terminal 10 in step 520.

0041As explained above, when the client terminal 10 requests a session reestablishment, the server 110 sends only data updated during disconnection (after termination of previous access) to the client terminal 10, without sending unchanged data. Thus, an efficient session reestablishment in terms of traffic and time is achieved.

0042Although preferred embodiments of the present invention have been described for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible without departing from the scope of the invention as disclosed in the accompanying claims.