A METHOD OF CONTROLLING CONNECTIONS IN A TELECOMMUNICATION SYSTEM

Abstract: User terminals (14-15) are connected to a telecommunication system. The telecommunication system comprises a control system (3) for the control, such as set-up, release and modification, of connections between the user terminals. A large portion of functions are common for control of dynamical as well as semi-permanent connections. Control of a connection can be initiated from any of the user terminals to which the connection relates, or from other user terminals. Control data for the connections can be stored in different types of storage resources in the control system, said different types of storage resources (20, 21, 24) having different degrees of reliability.

Description: A method of controlling connections in a telecommunication system TECHNICAL FIELD OF THE INVENTION The present invention relates to a method of controlling connections in a telecommunication system to which user terminals are connected. The telecommunication system comprises a control system for connection control, such as set up, release and modification of connections between user terminals. The control system comprises control resources as well as storage resources. The storage resources store control data related to said connections. In particular the invention relates to a method of the indicated kind in a system that handles dynamic connections as well as semi-permanent connections. PRIOR ART U.S. Patent Serial No. 5 107 489 discloses a switch with an associated protocol for set up of dynamical connections by using frames. Each frame comprises an identifier identifying the source and the destination of the frame as well as link control information for maintenance, establishment and release of a connection between source and destination. U.S Patent Serial No. 5 115 425 discloses a distributed switch system comprising switch modules in a network. A call is handled in one of two modes. In a first mode unoccupied or free connec¬ tions through the switch are selected quite regardless of if they are already established or not. In a second mode connections which are already established are selected. U.S. Patent Serial No. 5 051 982 discloses a method and a system for fast set-up of circuit switched virtual connections in a digital circuit switched switch that integrates speech and data by using a common switch, a common control system and a common distribution system. Non-used bandwidth can be retrieved and dynamical connections can be so re-arranged that bandwidth utilization is optimized, thus providing for a maximum data speed at any time. U.S. Patent Serial No. 4 821 256 relates to a method or monitor¬ ing information transmission in semi-permanent established 4-wire connections in digital time multiplex switches. Monitoring takes place by comparing bit streams and parity tests. U.S. Patent Serial No. 5 046 183 relates to an arrangement so designed that when there is a call that should be debited the receiver or a third party, or when there is a personal call, an operator needs to be involved only after the call has been set up; the type of the call being displayed to the operator so as to assist the operator. DE 38 18 087 relates to a telephone conference system comprising a permanent memory storing data relating to a number of partici¬ pants which are to join a telephone conference. From one conference participant telephone conference connections can be set up to other conference participants. RELATED ART A telecommunication system of the kind referred to above provides telecommunication services for which different types of connec¬ tions between the user terminals can be controlled, such as for example be set up, be released and be modified. For a first connection type said control is initiated from a user's terminal, for example a telephone or a computer. A user can initiate said control without involving an operator. The number of connections of this first type usually varies strongly over the time as does the respective durations of the connec¬ tions; said durations often being short, for example some minutes or hours. Accordingly, connections of this type are very flexible. Such connections will in the following therefore be referred to as dynamical connections. An advantage of a dynamic connection is the swiftness by which it can be controlled and the simple way in which the control takes place. For a second connection type said control is initiated by an operator of an operation and support terminal in an operation and support system. Connections of the second type usually are of a long duration, for example in the order of months. Compared with dynamical connections they are more static by nature. In the following, connections of the second type will be referred to as semi-permanent connections. An advantage of a semi-permanent connection is that it is less sensitive to disturbances, such as for example a non-desired release of the connection, than is a dynamic connection. This ability of not disturbing a connection is referred to as robustness. The robustness of semi-permanent connections is better than that of dynamical connections and is provided by storing control data related to semi-permanent connections more reliably than control data related to dynamical connections. Said more reliable storage of control data is in the following referred to as persistent storage. To control dynamical connections a first set of functions is used in the telecommunication system. To store semi-permanent connections a second set of functions is used. A majority of the functions of said second set are resident in a separate operation support system and are thus to a great extent separated from said first set of functions. By using functions from said first set of functions, the control of dynamical connections can be initiated from a user's terminal, for example a telephone or a computer. Functions from said second set of functions are used to control connections of high robustness and said control is initiated from said operation support system. A problem associated with the control of semi¬ permanent connections from within an operation support system is that it takes a long time for a user until a robust connection is set up. This is so because the user must first inform the operator of the telecommunication system and then the operator must set up the connection. This is a process that takes a long time, perhaps several days. The telecommunication system comprises several switching nodes interconnected in a network. The robustness of a dynamic connection that passes through several such switching nodes is low. In accordance with prior art technique the robustness of dynamical connections is increased for example by using more reliable hardware such as processors and switches which entails additional costs. The additional costs present a problem. Dynamical connections make use of control resources such as processing capacity of a processor included in the control system, and volatile data storage resources such as RAM memories. The amount of control resources and data storage resources as used is proportional to the number of dynamical connections that have been set up. The supply of resources is scarce and will limit the number of dynamical connections that can be set up. This presents a problem. DESCRIPTION OF THE INVENTION The object of the present invention is to reduce the above mentioned problems relating to the telecommunication system. User terminals are connectable to the telecommunication system. The telecommunication system comprises a control system for control, such as set up, release and modification, of connections between said user terminals. The control system comprises control resources as well as storage resources. The storage resources store control data related to connections in the telecommunica¬ tion system. In particular, one object of the present invention is to combine the advantages of dynamical connections with the advantages of semi-permanent connections in a simple manner such that: (a) control of semi-permanent connections can be initiated from a user terminal, (b) the robustness of dynamical connections is possible to select such that it will be equal to that of semi-permanent connections, i.e. it is possible to modify robustness, (c) the capacity of a control system is increased, given a shortage of resources, such as processing capacity; or in other words given a predefined capacity the need of resources can be reduced. The above objects are achieved by the features indicated in the appending claims. The invention will provide a connection, irrespective of its type, with several of the good properties which in accordance with previously known technique are inherent either in dynamical connections or in semi-permanent connections. The control of a robust connection is initiated from a user's terminal, without the traditional operation support system. Thus a user himself or an operator initiates this control. There is no longer any need for a specific operation support terminal or for an operation support system for handling semi-permanent connections. Semi-permanent connections are controlled in generally the same manner as dynamical connections. In contrast to dynamical connections control data related to the semi-permanent connection will, however, be persistently stored so as to provide semi¬ permanent connections with a robustness that is higher than that of dynamical connections. Functions for control of dynamical connections are to a great extent re-used for the control of semi-permanent connections. The robustness of a connection can be changed. A modification of the robustness of a connection is initiated either directly at a user's terminal or is initiated from within the control system in response to a user's behavior. In the latter case the control system stores connection related control data in the different storage media so as to attain a predetermined robustness mean value. A sufficiently good robustness will thereby be attained without making unnecessary use of scarce resources, thus making it possible to cut costs or to increase the capacity of the control system. In US 5.051.982 there is no disclosure of connections having different robustness. Connection control data are stored in one type of storage resource only, namely in a RAM. BRIEF DESCRIPTION OF THE DRAWINGS The invention will be described in detail with reference to the accompanying drawings wherein, Figure 1 schematically illustrates a telecommunication system in which the invention is used, Figure 2 schematically illustrates a telecommunication system and an operation support system connected thereto, said telecom¬ munication system comprising several nodes, Figure 3 schematically illustrates a control system, comprising control functions and storage resources of the telecommunication system shown in Figure 1 or 2, Figure 4 schematically illustrates a method in accordance with the invention, said method being used in the control system shown in Figure 3, Figure 5 illustrates an inventive method for setting up a semi¬ permanent connection from a user's terminal, Figure 6 illustrates an inventive method for changing the robustness of a connections, said method being initiated by a user, Figure 7 illustrates an inventive method for changing the robustness of a connection after a predetermined time, Figure 8 illustrates an inventive method for changing the robustness of a connection under conditions of shortage of resources, and Figure 9 illustrates a simplified flow diagram for handling of a connection. DETAILED DESCRIPTION OF EMBODIMENTS One embodiment of the invention as used in the control system of a telecommunication system 1 is schematically illustrated in Figure 1. The telecommunication system 1 comprises a switch 2, for example a digital circuit connected time switch, and a control system 3. User terminals, such as telephones 4, 5 or computers 6, and external lines 7, such as for example trunks, are connected to the telecommunication system 1. The telecommunication system in which the invention is used may, in a manner known per se, comprise a network having several interconnected nodes 8 as shown in Figure 2. In Figure 2 there is also shown an operation support system 9. Connections between user terminals 4, 5 are controlled, for example set up, released or modified, by the control system which operates on switch 2 in Figure 1 or on the switches 2 in Figure 2. In Figure 3 the control system is shown in detail. The control system comprises control functions 10.1-10.6 and storage resources. The storage resources comprise primary memories of a first type 11 and of a second type 12 as well as a secondary memory 13. The control functions may directly or indirectly seize the different storage resources. In accordance with the invention the major part of the control functions of the control system for connection control is directly or indirectly common to control of all types of connections. The connection types concerned comprise dynamic connections as well as semi-permanent connections. A telephone 14 and a computer 15 represent the different types of connections; the telephone representing a dynamic connection and the computer a semi-permanent connection. The arrows shown in Figure 3 symbolize interworking between user terminals 14, 15, control functions 10.1-10.6 and storage resources 11-13. For example the two user terminals interwork directly with control functions 10.2, 10.3 which they have in common as well as indirectly with several other control functions 10.4-10.6 and storage resources 11-13. Control, such as set up, release and modification, of connections of the semi-permanent type is initiated by a user which invokes the common control functions. To this end the common control functions must allow for storage of connection related control data in storage resources that provide the connections with their appropriate properties. This will be discussed below. The primary memory 11 of the first type has a relatively low degree of reliability while the primary memory 12 of the second type has a higher degree of reliability because it has, in a manner known per se, a hardware support for write protection. The secondary memory 13, which is a disc memory, has the highest degree of reliability. Connections of the semi-permanent type shall usually have a high degree of robustness. Accordingly control data associated with such connections are stored in a primary memory of the second type and/or in the secondary memory thus providing the connec- tions with their appropriate properties. The primary memory of the second type and the secondary memory are available to the function 10.6 only in consequence of the above mentioned hardware support. Since said memories are available from the function 10.6 only, the reliability of these storage resources is increased. This constitutes one of several possible ways, known per se, which contribute to storage resources having high reliability. For reasons of simplicity the invention will in the following be described in a system having two types of data storage resources only. Said types are referred to as volatile and persistent respectively. To a person skilled in the art it is apparent that more than two types of data storage resources are possible, each type providing a respective degree of reliability. The control system also comprises control resources which can be seized by the control functions. Control resources comprise processing capacity of a processor, not shown. When connection related control data for a connection has been persistently stored, control resources will be released. The released control resources are now free and can be used by another connection. Also volatile data storage resources will be released when control resources are released and such free storage resources can be used for another connection. In accordance with an important feature of the present invention control data relating to connections of all types can be moved between the volatile and persistent data storage resources. Accordingly, control data can be moved from the volatile to the persistent data storage resources, and from the persistent to the volatile data storage resources. It is therefore possible to adapt the properties of a connection to meet desired require¬ ments, and the utilization of the resources of the control system is optimized, given said properties. Optimum utilization implies that only such resources are seized which are necessary for achieving sufficiently good properties. If control data are not stored in the persistent memory then, in the described embodiment, the volatile data storage resources will limit the number of simultaneous connections that can be handled by the telecommunication system. Further, the control resources will limit the extent to which control data can be moved between volatile data storage resources and persistent data storage resources. Movement of control data will namely require processing capacity. Accordingly, control data relating to highly flexible connections should therefore not be stored without restrictions in the persistent memory since, if done, this results in frequent and extensive movements of control data between the volatile data storage resources and the persistent data storage resources. With reference to Figures 4 and 5 a first method in accordance with the invention will be described. The main features of the method are the following: A connection is initiated from a user's terminal, control data for the connection are stored in a persistent memory, thereby providing the connection with a high degree of robustness. A user terminal 4 initiates the set up of a connection to a user terminal 5. The connection shall have the same robustness as is characteristic for a traditional semi-permanent connection. When the request for connection set up is made dynamical processes 16, 17 are created. Each process represents a respective control function. In the processes connection related control data are manipulated by procedures 18, 19 which are implemented in program logic. Connection related control data belonging to the respec¬ tive processes are stored in a respective volatile memory 20 and 21. The processes are responsible for the set up of the connec¬ tion, box 22 in Figure 4, in a manner known per se. Following this connection related control data is copied, box 23, from the volatile memories 20, 21 to the persistent memory 24. Next volatile data storage resources are released, box 25, when the dynamical processes 16, 17 cease. A second method will now be described with reference to Figure 6. This method will have the following main features: A connection is set up between two user terminals to begin with and after a period of time the robustness of the connection is modified on the initiative of any one of the user terminals. A connection having a robustness that is lower than the highest robustness is set up from a user's terminal, box 26. Thereafter a modification of the properties of the connection is requested from any one of the user terminals 4, 5. In particular it is requested that the robustness of the connection be increased. Next there is a state of waiting for an order to be issued from any one of the user terminals, box 27. The connection related control data is copied from volatile memories to persistent memories, box 28. Thereafter the dynamical processes cease and control resources as well as volatile storage resources are released, box 29. A third method will be described next in connection with Figure 7. A robustness requirement sometimes means that a statistical mean value of disturbance probability relating to several connections may not be larger than a predetermined value. An inventive method to fulfil the above requirement is, during certain phases of the control of a connection, such as during the set-up phase, to store connection related control data for the connection in a volatile memory and to, during other phase, such as during data phase, store the connection related control data in a persistent memory. After a certain time, for example after 15 min. in data phase, said time being so calculated that a sufficiently high robustness has been attained, the connection related control data are stored in a persistent memory. When storing the data in the persistent memory it is probable that the connection is of a relatively static nature, and thus no extensive processing capacity is seized. Said time is calculated in advance, for example during system configuration, or is calculated during operation. The method has the following main characteristic features: Set-up of a connection, box 30, wait for the calculated time, box 31, store of connection related data in a persistent memory, box 33 and, as a consequence, release resources, box 32. A fourth method will be described next in connection with Figure 8. When the amount of resources as occupied by connections exceeds a predetermined limit, then a function in the control system selects those connections the control data of which are to be stored in another type of storage resource. When the storage of the connection related control data has been completed control resources as well as storage resources are released in a manner described above. Said function selects the connections according to different criteria, among these the duration of a connection and the type of connection. If a connection has lasted for more than for example 10 minutes there is a high probability that the connection will last for still a good time and therefore its connection related control data are stored in another type of storage resources so as to release resources which can be used for set-up of additional connections. In this case connections are selected based upon a user's behavior. This fourth method has the following characteristic features: A number of connections are set-up, box 34, when resources shortage begins, box 35, control data relating to selected connections are stored in another type of storage resource, box 36, thus making the released resources available, box 37. In order to maintain a stipulated minimum robustness for dynamical connections that pass through several switching nodes control data relating to said connections are stored persistent¬ ly. In Figure 9 a simplified block diagram for handling of a connection in accordance with invention is shown. The control system receives signals from the user terminals. A signal "off hook" indicates that a user terminal initiates set-up of a connection. Another signal, "type of connection", tells the control system if the connection shall be a semi-permanent or a dynamic connection. Still another signal "on hook" indicates that the connection shall be released. Functions which are previously known per se and which measures the amount of resources available in the control system will : release processor capacity in a processor, release data storage resources, perform time measurements, count the number of nodes through which a connection passes, store connection related control data persistently and will move connection related control data from persistent storage to volatile storage. These functions will therefore not be described in detail. The flow diagram will be described next. The control signal waits for the signal "off hook" at selection box 38. If the amount of available resources is high, selection box 39, if the connection is a dynamic connection, selection box 40, and if the connection passes through just one node, selection box 41, then the control data associated with the connection is stored in volatile memories, box 42. On the other hand if the amount of available resources is low, alternative, "low" at selection box 39, if the connection is a semi-permanent connec- tion, selection box 40, or if the connection passes though several nodes, selection box 41, then the control data associated with the connection is stored persistently thus releasing processing capacity for the processor, i.e. thus releasing control resources as well as volatile memories, box 43. If a dynamic connection lasts for a certain predetermined time, selection box 44, for example 10 minutes, then the control data associated with the connection are stored persistently and processing capacity in the processor as well as volatile memories will be released, box 43. If the signal "on hook" is detected, selection box 45, then processing capacity as well as volatile memories will be released, box 50, and the control system will then wait for the signal "off hook", box 38. Following the storage of persistent data, box 43, the control system waits for a signal "on hook", box 46. If the amount of resources is low, alternative "low" at selection box 47, then, after reception the signal "on hook", selection box 46, resources belonging to other connections will be released, box 48. Control data relating to said connections will now be stored persistently and said connections will be selected based upon how long they have lasted. Resources which are released at box 48 will be sized and the control data is stored in volatile memory resources, box 49. At box 50 resources are released and the "on hook" signal, is awaited, selection box 38. It is obvious to the man skilled in the art that the telecommuni¬ cation system in which the invention is applied, in manner known per se may comprise a control system which physically is distributed over several nodes (distributed control system) for example over the nodes shown in Figure 2.

Claims: CLAIMS 1. A method of controlling connections in a telecommunica¬ tion system (1) to which user terminals (4-6, 14-15) are connected, said telecommunication system (1) comprising a control system (3) for control, such as set-up, release and modification, of said connections between said user terminals (4-6, 14-15) , said control system comprising control resources as well as storage resources (11-13, 20, 21, 24) , the latter storing control data associated with said connections, characterized in that control functions for control of dynamical connections, among said control functions functions for set-up, release and modification of connections, are used for control of semi¬ permanent connections, and that the control of the semi-permanent connections is initiated from the user terminals (4-6, 14, 15) in cooperation with said control functions. 2. A method in accordance with claim 1, characterized in that control of the connections is initiated from the same user terminals as those to which the controlled connections refer. 3. A method in accordance with claim 1, characterized in that control of said connections is initiated from other user terminals than those to which the controlled connections refer. 4. A method in accordance with claim 1, 2 or 3 characterized in that control data relating to said connections are stored in different types of storage resources (20, 21 and 24 respectively) of the control system, said different types mutually having different degrees of reliability. 5. A method in accordance with claim 4, characterized in that the robustness of a connection is changed by moving control data relating to said connection between said different types of storage resources, said storage resources having mutually different reliabilities so as to provide different degrees of robustness . 6. A method in accordance with claim 5, characterized in that the robustness of a connection initially is selected low and, after a certain time is increased by first storing the control data of the connection in a storage resource (11, 20, 21) of the type that has low reliability, and thereafter moving said control data to a storage resource (12, 13, 24) of a type having a higher reliability. 7. A method in accordance with claim 6, characterized in that one type of a storage resource (11) comprises a RAM-memory, another type of storage resource comprises a RAM-memory (12) provided with hardware support for write protection, and a third type of storage resource comprises a disc memory (13). 8. A method in accordance with any of claims 4-7, character¬ ized in that resources of the control system are released when connection related control data are stored persistently. 9. Method in accordance with claim 8, characterized in that resources are released when predetermined conditions are fulfilled. 10. Method in accordance with claim 9, characterized in that one of said conditions is high control system load. 11. Method in accordance with claim 9 or 10, characterized in that at least one of said conditions is associated with user behavior. 12. Method in accordance with any of claims 9, 10 or 11, characterized in that at least one of said conditions is associated with the service used in a connection that has sized a resource. 13. A method of increasing the robustness of a dynamic connection in a telecommunication system provided with a control system that comprises program controlled functions for control, such as set-up, release and modification, of the connection, characterized in that the robustness of the connection initially is selected low, that after a certain time the robustness is increased by first storing control data relating to the connec- tion in a storage resource (11, 20, 21) of a type that has low reliability and thereafter moving said control data to a storage resource (12, 13, 24) of the type that has a higher reliability. 14. A method in accordance with claim 13, characterized in that a storage resource (11) of one type comprises RAM-memory means, that a storage resource of another type comprises RAM- memory means (12) provided with hardware support for write protection, and that a third type of storage resource comprises disc memory means (13) . 15. A method in accordance with claim 13 or 14, characterized in that the robustness of the dynamical connection is selected by storing control data relating to the connection in a storage resource of a type that provides the desired robustness. 16. A method in accordance with claim 15, characterized in that the robustness of a connection is changed by moving the control data of the connection between said different types of storage resources (20, 21 and 24 respectively) . 17. A method for increasing resources of a control system that is included in a telecommunication system, said control system comprising program controlled functions for control, such as set-up, release and modification, of connections between user terminals, characterized in that connection data related to selected connections initially are stored in a storage resource (11, 20, 21) of a type that has low reliability, and thereafter are moved to a storage resource (12, 13, 24) of a type that has a higher reliability, thus releasing resources in the control system. 18. A method in accordance with claim 17, characterized in that said connections are selected in accordance with predeter- mined conditions. 19. A method in accordance with claim 18, characterized in that said connections include high control system load. 20. A method in accordance with claim 19, characterized in that at least one of said conditions is associated with a user's behavior. 21. A method in accordance with any of claims 17-20, characterized in that at least one of said conditions is associated with the service used in a connection that has sized a resource. 22. A device for controlling connections in a telecommunica¬ tion system that comprises user terminals, a control system having functions for controlling connections between user terminals as well as functions for storing of control data, and storage resources comprising at least a volatile memory and at least a persistent memory, characterized by a mechanism which is sensitive to instructions generated at user terminals or at a terminal of an operator of the telecommunication system so as to move control data relating to a predefined connection from the volatile memory to the persistent memory.

Inventors: ANDERSSON STAFFAN, BOGREN ERIK LENNART, LINDBERG TORGNY ANDERS, NOVAK LARS, ANDERSSON, STAFFAN, BOGREN, ERIK, LENNART, LINDBERG, TORGNY, ANDERS, NOVAK, LARS
Applicants: ANDERSSON STAFFAN, BOGREN ERIK LENNART, ERICSSON TELEFON AB L M, LINDBERG TORGNY ANDERS, NOVAK LARS, ANDERSSON, STAFFAN, BOGREN, ERIK, LENNART, LINDBERG, TORGNY, ANDERS, NOVAK, LARS, TELEFONAKTIEBOLAGET LM ERICSSON (PUBL)
Application year: 1996
Main classification: H04Q11
IPC codes: H04Q3