Abstract:
A communication system for allocating a PVC to a user terminal connected through an ATM network interface to an ATM network includes: a PVC control server connected through an ATM interface to the ATM network; a switching system disposed in the ATM network for connecting the user terminal to the PVC control server through an SVC according to a virtual path identifier (VPI) and virtual channel identifier (VCI) generated by the user terminal; and an operator controlled workstation connected to the switching system for checking the state of the switching system, and for generating a signal in accordance with the acceptance or rejection of the user terminal&#39;s demand on the PVC. The latter signal is provided to the PVC control server upon receiving PVC demand data from the user terminal through the PVC control server, the acceptance or rejection signal being transferred through the SVC to the user terminal.

Description:
CLAIM OF PRIORITY 
     This application makes reference to, incorporates the same herein, and claims all benefits accruing under 35 U.S.C. §119 from an application for METHOD FOR CONSTRUCTING AND CONTROLLING A PRIVATE LINE BY MEANS OF A SWITCHED VIRTUAL CIRCUIT IN AN ATM NETWORK earlier filed in the Korean Industrial Property Office on the 8 th  of Apr. 1998 and there duly assigned Ser. No. 12401/1998. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a technique for constructing and managing a private communication line for a user terminal using a switched virtual circuit in an asynchronous transfer mode (ATM) network. 
     2. Description of the Related Art 
     Generally an ATM network includes a permanent virtual circuit (PVC) for allocating a fixed channel to a user terminal, and a switched virtual circuit (SVC) connected to the user terminal on the basis of a connection demand, the two circuits being complementarily used. In this case, the user terminal usually uses the SVC to transmit and receive data, and therefore, in order to obtain a private service line, the user must request setting of it by the operator of a telephone exchange office or network control center by calling through a public switched telephone network (PSTN). Then, the operator operates the work station controlling the ATM network connected to the user terminal to check whether its link bandwidth may be allocated to the user terminal. If there remains a portion of the link bandwidth to allow for the user&#39;s demand, he sets the PVC by operating the workstation. Thereafter, he notifies the user of the setting by telephone, so that the user may use the PVC. Thus, in order to receive the PVC of the ATM network, the user must call up the operator of the ATM network system through the PSTN. This also requires the operator to control private line services according to the user&#39;s demand, degrading the efficiency of controlling the PVC. 
     The following patents disclose features in common with the present invention but do not teach or suggest the specifically recited technique for constructing and controlling a private line using a switched virtual circuit in an ATM network: U.S. Pat. No. 5,848,068 to Daniel et al, entitled ATM COMMUNICATION SYSTEM INTERCONNECT/TERMINATION UNIT, U.S. Pat. No. 5,854,789 to Lesch et al., entitled ATM COMMUNICATION SYSTEM WITH A MODULAR STRUCTURE AND COMMUNICATION MODULES, U.S. Pat. No. 5,680,396 to Moritomo et al., entitled COMMUNICATION METHOD, TRANSMISSION APPARATUS, RECEPTION APPARATUS, AND TRANSMISSION LINE BANDWIDTH CONTROL APPARATUS FOR PVC CONNECTION TYPE SWITCHED NETWORK, U.S. Pat. No. 5,886,982 to Kozaki et al., entitled ATM SWITCHING SYSTEM AND CELL CONTROL METHOD, U.S. Pat. No. 5,530,698 to Kozaki et al., entitled ATM SWITCHING SYSTEM AND CELL CONTROL METHOD, U.S. Pat. No. 5,631,903 to Dianda et al., entitled TELECOMMUNICATIONS SIGNALING ARRANGEMENTS FOR TERMINALS WITHOUT SIGNALING CAPABILITY, U.S. Pat. No. 5,200,952 TO Bernstein et al., entitled ADAPTIVE VCP CONTROL IN INTEGRATED SERVICES NETWORKS, U.S. Pat. No. 5,539,884 to Robrock II, entitled INTELLIGENT BROAD BAND COMMUNICATION SYSTEM AND METHOD EMPLOYING FAST-PACKET SWITCHES, U.S. Pat. No. 5,048,087 to Trbovich et al., entitled KEY MANAGEMENT FOR ENCRYPTED PACKET BASED NETWORKS, U.S. Pat. No. 5,023,780 to Brearley, entitled METHOD OF OPERATING A PACKET SWITCHING NETWORK, U.S. Pat. No. 5,014,262 to Harshavardhana, entitled APPARATUS AND METHOD FOR DETECTING AND ELIMINATING CALL LOOPING IN A NODE-BY NODE ROUTING NETWORK, U.S. Pat. No. 4,965,804 to Trbovich et al., entitled KEY MANAGEMENT FOR ENCRYPTED PACKET BASED NETWORKS, and U.S. Pat. No. 5,781,529 to Liang et al., entitled SYSTEMS AND METHODS FOR ROUTING ATM SWITCHED VIRTUAL CIRCUIT CALLS. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to provide a method of obtaining private line service only through an ATM network without using a PSTN. 
     It is another object of the present invention to provide a communication system comprising a PVC control server for automatically controlling the PVC in an ATM network. 
     According to an aspect of the present invention, a communication system for allocating a PVC to a user terminal connected through an ATM network interface to an ATM network comprises: a PVC control server connected through an ATM interface to the ATM network; a switching system disposed in the ATM network for connecting the user terminal to the PVC control server through an SVC according to a virtual path identifier (VPI) and virtual channel identifier (VCI) generated by the user terminal; and an operator controlled workstation connected to the switching system for checking the state of the switching system and for generating a signal representing the acceptance or rejection of the user terminal&#39;s demand on the PVC to the PVC control server upon receiving PVC demand data from the user terminal through the PVC control server, the acceptance or rejection signal being transferred through the SVC to the user terminal. 
     According to another aspect of the present invention, a method of allocating the PVC to the user terminal in a communication system as described above comprises the steps of: demanding a connection to the ATM network by the user terminal generating a predetermined VPI and VCI through a signal channel; connecting the user terminal to the PVC control server in response to the VPI and VCI; sending a connection signal and initial data from the PVC control server to the user terminal; displaying the initial data on the user terminal; sending the PVC demand data to the PVC control server; transferring the PVC demand data to the operator controlled workstation for checking the switching system and for generating the acceptance or rejection signal transferred to the user terminal; and shifting the connection of the user terminal to the PVC upon receiving the acceptance signal. 
     The present invention will now be described more specifically with reference to the drawings attached only by of example. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     A more complete appreciation of the invention, and many of the attendant advantages thereof, will be readily apparent as the same becomes better understood by reference to the following detailed description when considered in conjunction with the accompanying drawings in which like reference symbols indicate the same or similar components, wherein: 
     FIG. 1 is a schematic diagram illustrating the construction of an ATM network to perform on-line control of a PVC according to the present invention; 
     FIG. 2 is a block diagram illustrating the structure of the functional data entry of a user terminal and a PVC control server; and 
     FIG. 3 is a flowchart illustrating the steps for obtaining the PVC by means of an SVC according to an embodiment of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring to FIG. 1, a user terminal  101  is connected through an ATM interface line  11   a  to an ATM network  100 , which is provided with a plurality of switching systems  20 ,  30 ,. . . transmitting ATM cell data, and in turn connected to a PVC control server  102  via line  11   b.    
     The PVC control server  102  may be installed in a telephone exchange office or network control center. Of course, the telephone exchange office may serve as the network control center. When the PVC control server  102  is installed in the telephone exchange office, it is connected to an operator controlled workstation  103  to control the switching systems. In this case, the operator controlled workstation  103  is connected through Ethernet line  10   a  to the ATM switching system  20 . In addition, the PVC control server  102  is connected through a data line  12  to the operator controlled workstation  103 . In the present case, the PVC control server  102  installed in the telephone exchange office is not connected to the network control computer  105 , telecommunication management network (TMN)  50  and switching system control computer  104 . Conversely, if the PVC control server  102  is installed in the network control center, it is not connected to the operator controlled workstation  103 . On the other hand, if the PVC control server  102  is installed in the telephone exchange office additionally serving as the network control center, the connection is established as shown in FIG.  1 . 
     Describing the operation of the PVC control server  102  installed in the telephone exchange office not serving as the network control center, the operator controlled work station  103  receives the state information concerning the channel allocation of the switching system  20 . The user terminal  101  sends a call signal to the ATM network  100  to connect through the ATM line  11   b  to the PVC control server  102 . Thereafter, the user terminal  101  transmits the VPI and VCI through the signal line  11   a  to connect to the PVC control server  102 . The values of the VPI and VCI, for example, are set to VPI=0 and VCI=5. Receiving these values VPI=0 and VCI=5, the switching system of the ATM network  100  connects the user terminal  101  to the PVC control server  102 . Then, such connection is the SVC. Of course, the value of the VPI and VCI may be changed as desired. Through this SVC, the user terminal  101  asks the PVC control server  102  for connection to the PVC. To this end, the user terminal generates data representing the transmission speed and service time to use the PVC. This data, which is hereinafter referred to as ‘PVC demand data’, is transferred to the PVC control server  102 , which in turn transfers the PVC demand data to the operator controlled workstation  103 . Then, the workstation  103  checks the state of the switching system  20  to determine whether to accept or reject the PVC demand data, transferring a signal representing the acceptance or rejection of the PVC demand data to the PVC control server  102 , which in turn sends the acceptance or rejection signal through the ATM network  100  to the user terminal. 
     On the other hand, describing the operation of the PVC control server  102  installed in the network control center without the operator controlled workstation  103 , the PVC control server  102  sends the PVC demand data through a data line  13  to a network management workstation or network management computer (NMC)  105 , which is connected through TMN  50  to a workstation  104  to control the ATM switching system  30 . The workstation  104  and switching system  30  are connected by means of Ethernet line  10   b . The switching system control workstation  104  checks the switching system  30  to determine whether to accept or reject the PVC demand data, as the operator controlled workstation, and then transfers the acceptance or rejection signal through TMN  50  to the workstation  105 , which in turn transfers the acceptance or rejection signal to the PVC control server  102 . The remaining steps are the same as in the previous case where the PVC control server  102  is installed in the telephone exchange office. 
     Referring to FIG. 2, the user terminal  101  and PVC control server  102  consist of  4 -layer hierarchy. The hierarchical structure of the user terminal  101  consists of PVC client layer  201 , third layer  202 , second layer  203  and  204 , and ATM layer  205 . The third layer  202  and second layer  203  and  204  constitute the signaling stack. Since the PVC demand data is transmitted through the signal channel, the second layer consists of the signal ATM adaptation layer (SAAL)  203  and ATM adaptation layer  5  (AAL 5 )  204 . Likewise, the hierarchical structure of the PVC control server  102  consists of PVC server layer  211 , third layer  212 , second layer  213  and  214 , and ATM layer  215 . The second layer consists of SAAL  213  and AAL 5   214 . The third layer  212  and second layer  213  and  214  constitute the signaling stack. 
     Describing the procedure of obtaining the PVC by means of the PVC control server  102  connected to the operator controlled workstation  103  in the telephone exchange office, in connection with FIG. 3, the user terminal  101  loads the program to connect to the ATM network in step  300 , and proceeds to step  302  to check whether there is a key input to demand a connect to the ATM network  100 . If a signal demanding the connection is detected in step  302 , the user terminal  101  goes to step  304 ; otherwise, it goes to step  316 . In step  304 , the user terminal  101  generates a connection signal through the signaling stack consisting of the third layer  202 , SAAL  203  and AAL 5   204 , and transfers it through the ATM layer  205  to the ATM network  100 . The connection signal is the signal demanding a connection with the PVC. In this case, the signaling stack  202 ,  203 , and  204  generates the values VPI=0 and VCI=5 which are transmitted through the ATM layer  205 . Then, the switching system of the ATM network  100  transfers the signal identified as VPI=0 and VCI=5 to the PVC control server  102 . 
     When the PVC control server  102  is on standby in step  330 , it receives the connection signal, and it proceeds to step  332  to generate a connection answering signal notifying of establishment of the connection. Then, in step  334 , the PVC control server  102  transmits the initial data through the ATM interface fines  11   b  and  11   a  to the user terminal  101 . Receiving the initial data in step  306 , the user terminal  101  displays the received data on the monitor of the operator controlled workstation  103 . Then, in step  308 , the user terminal  101  receives the PVC demand data inputted by the user, and transmits it through the ATM network  100  to the PVC control server  102  in response to the key input demanding its transmission. The PVC demand data represents the bandwidth and service time to use the PVC. After receiving the PVC demand data in step  336 , the PVC server  102  proceeds to step  338  to transfer the PVC demand data to the operator controlled workstation  103 . 
     When the workstation  103 , on standby in step  360 , receives the PVC demand data in step  362 , it proceeds to step  364  to check the state of the switching system  20  to determine whether there is an available bandwidth. Then, in step  366 , the operator controlled workstation  103  generates a signal representing the acceptance or rejection of the PVC demand data and provides that signal to the PVC control server  102 . Receiving the signal representing the acceptance or rejection in step  340 , the PVC control server  102  transmits it through the ATM network  100  to the user terminal  101 . The acceptance or rejection signal generated in the PVC server layer  211  as shown in FIG. 2 is converted by the signaling stack consisting of the third layer  212 , SAAL  213  and AAL 5  into signaling data transmitted through the ATM layer  215  to the user terminal  101 . 
     Receiving and displaying the acceptance or rejection signal in step  310 , the user terminal  101  proceeds to step  312  to determine whether the PVC demand data is accepted or not. In this case, the acceptance or rejection signal is received through the ATM layer  205 , and is processed through the signaling stack to the PVC client  201 . Detecting the acceptance of the PVC demand data in step  312 , the user terminal  101  proceeds to step  318  to complete a connection with the PVC provided by the ATM network  100 . On the contrary, in determining the rejection of the PVC demand data instep  312 , the user terminal  101  proceeds to step  314  to determine whether there is a demand to change the PVC demand data. Detecting the demand to change the PVC demand, the process returns to step  308 ; otherwise, the process is terminated. Until now, although described in connection with the PVC control server  102  installed in the telephone exchange office, the procedure may also be applied to the PVC control server  102  installed in the network control center. 
     As described above, the PVC control server makes the user terminal directly demand a connection with the PVC through the SVC, so that the user need not call up the operator of the exchange office through the PSTN. While the present invention has been described with specific embodiments accompanied by the attached drawings, it will be appreciated by those skilled in the art that various changes and modifications may be made thereto without departing from the gist of the present invention.