Abstract:
A switching system performs internally a terminal process for an AO/DI traffic directly without using a packet handler and includes a subscriber switching subsystem to thereby communicate with Internet through a router within the subscriber switching subsystem. Therefore, the switching system simplifies an ISDN call process procedure for the AO/DI service and prevents a switching resource within the switching system from being inefficiently managed to thereby provide much more subscribers with the AO/DI service.

Description:
FIELD OF THE INVENTION  
         [0001]    The present invention relates to a switching system; and, more particularly, to a switching system for providing an always on/dynamic ISDN (AO/DI) service through a subscriber switching subsystem without using a RAS (Remote Access Server) to thereby minimize a usage of a switching resource and simplify an ISDN call process procedure within the ISDN switching system.  
         BACKGROUND OF THE INVENTION  
         [0002]    In general, as a bi-directional communications service that uses an idle ISDN (Integrated Services Digital Network) D-channel which is not used by a subscriber of an ISDN BRI (Basic Rate Interface), AO/DI (Always On/Dynamic ISDN) service provides a various services such as E-mail (Electric mail), a news, a credit card inquiry and a various Internet services by maintaining an “always on” connection between a subscriber&#39;s terminal and a contents server via the contents server and a packet handler of a switching system.  
           [0003]    A conventional system has the contents server as a RAS (Remote Access Server) in an outside of the switching system and provides the AO/DI service by performing communications through an ISDN PRI (Primary Rate Interface) between the contents server and the switching system.  
           [0004]    Referring to FIG. 1, there is provided a block diagram of a conventional system providing the AO/DI service. An AO packet data path is set up as follows: at the instant AO/DI terminal  101  is turned on, a D-channel packet call set-up is automatically requested from the AO/DI terminal  101  to an ISDN switching system  110 . The ISDN switching system  110  performs a D-channel packet process over a subscriber switching circuit  111 , a time switch  112  and a D-channel packet handler  113 , and a B-channel packet process over a space switch  114 , a B-channel packet handler  115 , a time switch  116 , PRI  117  and an AO/DI server  120  to thereby set up an AO packet data path between the AO/DI terminal  101  and the AO/DI server  120  and transmit the packet data while maintaining “always on” state until a power of the AO/DI terminal  101  is turned off. Consequently, the subscriber receives various services of a slow speed data under 9.6 Kbps transmitted through the AO packet data path.  
           [0005]    But, if the subscriber requests a mass file transmission of more than 9.6 Kbps through an access to the Internet, the AO/DI terminal  101  requests for a usage of the ISDN B-channel from the ISDN switching system  110  and the ISDN switching system  110  sets up a switching path for an ISDN B-channel call process over the subscriber switching circuit  111 , the time switch  112  and the PRI  117 , and a DI packet data path by doing a PRI switching process between the PRI  117  and the AO/DI server  120 , i.e., the contents server of an RAS structure to thereby transmit the rest of the packet data which cannot be transmitted through the AO packet data path.  
           [0006]    As mentioned above, in case that the AO/DI terminal  101  requests the data transmission only through the AO packet data path, the ISDN switching system  110  provides the services over a X.25 packet handler to thereby transmit the packet data between the AO/DI terminal  101  and the AO/DI server  120 , and in case that the AO/DI terminal  101  requests the B-channel setup for a mass data transmission, the ISDN switching system  110  provides the B-channel path between the AO/DI terminal  101  and the AO/DI server  120  over a switching path regardless of the packet handler.  
           [0007]    However, when the AO/DI service is provided from the ISDN switching system  110 , in order to increase the capacity of the AO/DI service subscriber, the physical transmission line should be extended and the occupation rate of a switching resource will also increase, thereby increasing the chance that the switching resource will be managed inefficiently.  
         SUMMARY OF THE INVENTION  
         [0008]    It is, therefore, an object of the present invention to provide an always on/dynamic ISDN (AO/DI) service through a subscriber switching subsystem without using a RAS (Remote Access Server) to thereby minimize the use of a switching resource and simplify an ISDN call process procedure within the ISDN switching system.  
           [0009]    In accordance with the present invention, there is provided a switching system for providing an AO/DI service to at least one subscriber terminal, wherein the switching system includes a subscriber switching subsystem, which includes:  
           [0010]    a subscriber switching circuit for performing a layer  2  protocol process for providing the AO/DI service to the subscriber terminal; a device controller for reading a packet data stored in the subscriber switching circuit and adding a corresponding subscriber information to the packet data to transmit the packet data in case an AO path set-up is requested from the subscriber terminal, but also for transmitting the original packet data without adding the corresponding subscriber information in case the packet data provided is to be transmitted through a DI path established for the subscriber terminal; a server for requesting the AO path set-up for the subscriber terminal and the DI path set-up for the subscriber terminal in case the amount of data transmitted from Internet exceeds a predetermined threshold, and performing terminal processes of a layer  3  protocol and PPP for the packet data transmitted through the AO path and the DI path; a message switch module having an n×n switching structure for transmitting the packet data provided from the device controller to a corresponding server or the packet data provided from the server to a corresponding device controller through a self-routing by using the subscriber information included in the packet data; a high process for setting the DI path for a channel corresponding to an additional bandwidth when the packet data transmitted from the subscriber switching circuit or the server includes a request for setting up the DI path; and a router for transceiving the packet data between the server and the Internet by using an IP address included in the packet data. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0011]    The above and other objects and features of the present invention will become apparent from the following description of preferred embodiments given in conjunction with the accompanying drawings, in which:  
         [0012]    [0012]FIG. 1 shows a block diagram of a conventional system providing the AO/DI service; and  
         [0013]    [0013]FIG. 2 presents a block diagram of a system providing the AO/DI service by using an ISDN switching system in accordance with the present invention. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0014]    Referring to FIG. 2, there is provided a block diagram of a system providing the AO/DI service by using an ISDN switching system in accordance with the present invention. The system comprises an AO/DI terminal  201 , an ISDN switching system  210  and Internet  220 , wherein the ISDN switching system  210  includes a subscriber switching subsystem  211  that is improved in accordance with the present invention.  
         [0015]    The subscriber switching subsystem  211  includes a subscriber switching block  212  for performing a switching process between the AO/DI terminal  201  and the ISDN switching system  210  by processing a layer two protocol for data transceiving with the AO/DI terminal  201 , an MSM (Message Switch Module)  215  connected to the subscriber switching block  212  through a U_link, an AO/DI server  216  connected to the MSM  215  through the U_link, a high process  217  for the AO/DI server  216  and the subscriber switching block  212 , and a router  218  connecting the AO/DI server  216  to the Internet  220  in order to communicate in an environment such as a LAN (Local Area Network). The U_link has a structure synchronized with a clock signal of 8 MHz for transmitting data.  
         [0016]    In the system, when a power of the arbitrary AO/DI terminal  201  is supplied, the corresponding AO/DI terminal  201  requests for the D-channel packet call automatically.  
         [0017]    A subscriber switching circuit  213  within the subscriber switching block  212  processes the layer two protocol for the packet data transmitted through the D-channel from the AO/DI terminal  201  and then stores the processed packet data in a common memory (not shown) equipped within the subscriber switching circuit  213 . A device controller  214  reads the packet data stored in the common memory and then adds subscriber information on the corresponding packet data to a header region. The added subscriber information is information such as an SAI (Service Access Identifier), a TEI (Terminal End Identifier), a subscriber line number and etc. The packet data is transmitted to the MSM  215  through the U_link.  
         [0018]    The MSM  215 , which performs a self-routing on a byte basis for a transmitted message and has an n×n switching structure, transmits a message transmitted from the device controller  214  to the corresponding AO/DI server  216  and operates to transmit a message transmitted from the AO/DI server  216  to the corresponding subscriber switching block  212  by using the subscriber information in the header region of the message. Herein, the MSM  215  transmits the packet message transmitted from the subscriber switching block  212  to the AO/DI server  216  by multiplexing the packet message and transmits the packet message transmitted from the AO/DI server  216  to the subscriber switching block  212  by demultiplexing the packet message. The subscriber switching block  212  and the AO/DI server  216  included in the switching subsystem  211  play essential roles in the processes, respectively.  
         [0019]    The AO/DI server  216  analyzes the header information of the packet data received from the MSM  215  and provides an intrinsic call number. A method providing the intrinsic call number can be implemented in correlation with the total number of the subscribers provided with the AO/DI service by providing a number obtained by adding 1 to the number of the currently maintained D-channels. Herein, the provided call number is maintained when the call is released from the corresponding subscriber and the call release occurs until the AO/DI terminal is turned off.  
         [0020]    Next, the AO/DI server  216  performs a protocol terminal process for a layer  3 , analyzes a call request packet and then requests the high process  217  for a confirmation whether the corresponding subscriber is a legitimate subscriber for receiving the service. As a result of the confirmation request, if the subscriber is confirmed as a legitimate subscriber for receiving the service, the AO/DI server  216  transmits a setup completion packet of a call connection to the AO/DI terminal  201 . The setup completion packet is transmitted to the AO/DI terminal  201  through a path connecting the MSM  215  with the device controller  214  and the common memory (not shown) in the subscriber switching circuit  213  within the corresponding subscriber switching block  212 . Accordingly, the transmission path for a basic data is set up between the AO/DI terminal  201  and the AO/DI server  216 .  
         [0021]    By using the data transmission path, the AO/DI terminal  201  and the AO/DI server  216  perform a PPP (Point-to-Point Protocol) link setting, user authentication and IP (Internet Protocol) layer setting, connect each layer to perform a mutual PPP terminal process and assign an IP address to thereby make the Internet communications possible. The IP address is a 32-bit address defined in the Internet protocol.  
         [0022]    Subsequently, the AO/DI server  216  maps the assigned IP address to the call number to store the assigned IP address. That is to transmit the message between the router  218  and the MSM  215  through the corresponding path. And, the AO/DI server  216  transmits the PPP terminal processed packet data including the IP address to the router  218 .  
         [0023]    For the ISDN switching system  210  to provide the corresponding AO/DI terminal  201  with a corresponding service from the Internet  220  connected to the LAN environment, the router  218  performs a routing by using the IP address included in the received packet data to transmit the packet data to the Internet  220  and a routing by using the IP address included in a data transmitted from the Internet  220  to transmit the data to the corresponding AO/DI server  216 .  
         [0024]    As mentioned above, in a data transmission through the AO transmission path, in case the AO/DI terminal  201  or the AO/DI server  216  requests for a transmission of data whose amount exceeds a predetermined threshold, i.e., over 9.6 Kbps, an ISDN B-channel is added through the general ISDN call set-up procedure.  
         [0025]    Namely, if the AO/DI terminal  201  transmits the data whose amount secedes the predetermined threshold, the AO/DI terminal  201  requests for the ISDN call set-up to the ISDN switching system  210  through the D-channel. Herein, the call set-up request signal including information on the number of B-channels additionally needed is transmitted to the subscriber switching circuit  213  and the subscriber switching circuit  213  reports the call set-up request signal to the high process  217 . When the analysis of the call setup request signal indicates a request for an additional bandwidth assignment, the high process  217  allows the subscriber switching circuit  213  to assign number of B-channels corresponding to the requested bandwidth to the DI path of the corresponding AO/DI terminal  201 .  
         [0026]    Therefore, the subscriber switching circuit  213  treats the data transmitted from the AO/DI terminal  201  through the B-channels allowed by the high process  217  as the data for communicating with the Internet  220  and transmits the data to the device controller  214 . Then, the device controller  214  does not add the subscriber information to the data provided through the DI path and transmits the original data to the MSM  215 . The remaining transmission process of the data is identical to that of the data through the AO path.  
         [0027]    Meanwhile, in case of transmitting data the amount of which exceeds the predetermined threshold, the AO/DI server  216  requests for an additional bandwidth to the high process  217  and if a usage of a corresponding DI path is permitted by the high process  217 , the AO/DI server  216  transmits the remaining data which are not transmitted through the D-channel to the MSM  215  through the B-channel. The data transmitted to the MSM  215  is transmitted in a same way as the data transmitted to the AO/DI terminal  201  through the AO path.  
         [0028]    While the invention has been shown and described with respect to the preferred embodiments, it will be understood by those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the invention as defined in the following claims.