DISTRIBUTED CONNECTION CONTROL IN TELECOMMUNICATION NETWORKS

Abstract: The invention relates to a method for handling connection in a telecommunication system comprising digital, computer controlled telephone exchanges and subscribers connected thereto, wherein the connection handling is distributed out in the network. Physical connections between subscribers are handled under control of abstract connection models, wherein in an object oriented system a number of different, mutually independent user processes are provided in such a manner that one or more of said processes under control of one or more processors control that or those connections which are necessary to achieve e.g. reservation of a connection path, connection set up, through-connection and release of a complete connection, and re-direction of connections. The invention solves the problem to coordinate a number of processes by means of a set of functional objects which allow each user to control and change a connection without coordination with other users. The method is called connection model and supports the setting up of connections in a communication network. The connection models comprise port objects representing connection end ports and connection objects representing abstract connections between end ports. When objects and models have been linked togheter in a chain, the connection can be physically set up via a connection set up function.

Description: Title: DISTRIBUTED CONNECTION CONTROL IN TELECOMMUNICATION NETWORKS TECHNICAL FIELD The invention relates to handling of connections in a tele¬ communication system comprising digital, computer controlled telephone exchanges and subscribers connected thereto, where¬ in the control of the handling of connections between sub- scribers in the network is distributed out in the network. BACKGROUND OF THE INVENTION In such a distributed telecommunication system it is possible that a plurality of more or less independent processes are involved in a connection. The processes can be controlled by one or more processors. Should each of these processes wish to control the connection or those connections which are ne¬ cessary in order to establish a call, some kind of coordina- tion between the processes has to take place. A number of solutions to that problem are previously known. a) An application-specific communication between processes is specified. This necessitates a dialogue between the processes to be established. By means of this dialogue, information about the requested connection is transferred and the state of the connection has to be hand shaken between the different processes. b) A process is defined as master. Only the master process can fully control the connection; the other processes can merely provide the master process with data, c) It is also possible to utilize a process for each switch in the network through which the connection is to be set up. EP 0 454 332 A2 presents a method for call handling in a te¬ lecommunication network comprising a matrix of physical net¬ work nodes, where the setting up of connections through the nodes takes place with support of an abstract model. BRIEF DESCRIPTION OF THE INVENTION The problems with the known methods are a) The solution with an application specific communication requires that all processes understand the specific communication in order to be able to execute the hand¬ shaking procedure. This solution requires a relatively comprehensive reconstruction for every new application. b) In the solution with a master process, said process constitutes the only controlling process. The other processes have very limited possibilities to control or change the setting up of connections. c) With one process per switch, the application (the user) has to have knowledge about the topology of the network. If a connection is set up through only one switch, only one user process can be utilized. The above European patent application solves the problem by establishing a physical connection with support of an ab¬ stract model but the system does not give any support for any coordination between a plurality of independent user proces¬ ses in a distributed system. The telecommunication network according to the invention sol¬ ves the problem mainly in that in an object oriented system, a plurality of different, mutually independent processes are arranged in such a manner that one or more of said processes under control of one or more processors are adapted to con¬ trol the handling of that or those connections which are ne¬ cessary to achieve e.g. reservation of a connetion path, con¬ nection set up, through-connection and release of a complete connection between subscribers or nodes in the network, and redirection of connections, wherein abstract connection paths are adapted to be set up by means of connection models in which different types of objects, e.g. connection objects, port objects and end port objects, are linked together, said linking being carried out by means of association or preliminary association, wherein upon association of connec¬ tion models, references in the form of signals exit from a port in a first connection model to a port in a second con¬ nection model, and that upon internal association within a connection model, references are supplied between adjacent connection objects and port objects, and that upon a set-up abstract connection between two end ports and between those associated connection objects, port objects and connection models, a physical connection is adapted to be set up by ex- changing references between abstract and physical access points, and that upon preliminary association, it is possible to associate a further access point from the same end port above a connection set up by normal association. The present invention relates to a system having an object oriented program structure implying that every logic compo¬ nent is implemented as a software object. The invention solves the problem to coordinate a plurality of processes by means of a general set of functional objects, which allows each user (process) to control and change a con¬ nection without coordinating this with other users. The method is called connection model. A connection model accor¬ ding to the invention supports the setting up of connections between network access points in a communication network. The model describes the interface between the users and the phy¬ sical network. A connection model comprises a set of connec¬ tion and port objects in the same user process, related to each other by association or preliminary association. The connection model allows each user (process) to have its own picture of the connection, i.e. its own connection model. The connection model enables the user to establish connec¬ tions alone or together with other users and to manipulate already established connections without any coordination with other users. The services that are offered to each user are: • Set up and release of connections. • Change of connection state, i.e. reservation and through- connection, respectively, of connections. • Connection supervision. • The possibility to logically define two connections to the same access point. • Redirection of a physical access point in an already estab¬ lished connection to a new access point by assigning an end object to this new access point (address) . The advantages of the method according to the invention is that it is possible to let a plurality of processes control a connection without any coordination procedure and without any knowledge about the topology of the network, e.g. through how many switches a connection is set up. The inventive idea is applicable in all types of communication systems having dis¬ tributed control. BRIEF DESCRIPTION OF THE DRAWING The method according to the invention will be described more in detail below by means of an embodiment with reference to the appended drawing on which Fig. 1 is a sketch which illustrates the linkage between a number of connection models and the physical network, Fig. 2 illustrates the association between two connection models and the internal association between ports and connections in each connection model, Fig. 3a is a sketch which illustrates the preliminary asso¬ ciation function in general, Fig. 3b illustrates the physical through-connection in a connection model and Fig. 4 illustrates in the form of a block diagram how traf¬ fic controlling functions in two processes together order a connection through the internal network by means of the connection model according to the inven¬ tion. PREFERRED EMBODIMENT To facilitate the understanding of the description of the invention, certain expressions that are used, are explained below. Process = A series of events that execute in an isolated environment with separate program and data memo¬ ry. Object = In an object oriented software system an object is the abstract transcription of a physically or logically definiable unit. Connection model = A comprehensive method for abstract hand¬ ling of connections; there can be several models for one connection. Connection = Abstract connection in a connection model. Port = Access point that can be called in a connection mo- del. The ports represent access points towards the physical network, in this case the switching network. The connection model is made up of objects of two classes, namely ports and connections. The port objects represent con- nection end points (access points) while the connection objects represent abstract connection between end points. To create a physical connection through the network, as appa¬ rent from Fig. 1, the users 1-3 according to the example have to link their models together in a chain. The association (connection) between the models is created by an exchange of references (signals) between the user processes and further association of these references to the port objects. A physi¬ cal connection is created in the network when all models are linked together and two access points are associated to the respective end of the chain. The expressions association, object etc. refer to the fact that it, in this object orien¬ ted system, is a matter of, in the first hand, creating abst- ract connections which can not be set up physically until an abstract set-up between models and end points is ready. What the invention comprises is essentially the interface between the service controlling functions and the physical network. By association is meant linkage both of different models and of the objects within a model which is illustrated in Fig. 2. The connection models are linked together by associating ports in different models to each other. The models are con¬ structed by associating connections to ports or other connec- tions. It is not necessary for the user to create the models or the objects in the models in any particular order. By preliminary association is meant that a port can be asso¬ ciated to a further connection object above the object the port normally is associated to as illustrated in Fig. 3a. A chain of connection models which comprises a preliminary as¬ sociation, can not physically be connected through as indica¬ ted in Fig. 3b where a normal association brings about a through-connection of a connection but where a preliminary association merely brings about a reservation of a connec¬ tion. By influencing the port object it is possible for the user to change a normal association into a preliminary asso¬ ciation and at the same time change a preliminary association into a normal association. Preliminary association can be used to implement such functions as "call waiting" or "acce¬ lerating a call upon a busy condition". As mentioned, preli¬ minary association is used merely for reservation of connec¬ tions but never for through-connection. An embodiment of the invention will be described in accordan¬ ce with the below example which with support of Fig. 4 and an arrow diagram illustrates the implementation of the connec¬ tion model function. • Said computer system is of a real-time system type having a support for executing software in parallel/"se iparallel" in so called processes. • There is support to set up dialogues and to communicate between the processes. • In the example chosen the function supports two service controlling functions ("applications") OC and TC, respec- tively, which are executed in two separate processes, one for originating call service for a subscriber A and one for terminating calls for a subscriber B. • These two processes communicate with each other by a so called service dialogue to transfer service information, i.e. information about how the connection is to behave. In this example this dialogue is called TSD (Teleservice Dia¬ logue) but other types of protocols which fulfil the par¬ ticular requirements of the application may also be used. The information that has to be transferred on this service dialogue between the processes in order to set up connec¬ tions, are those references that are needed to establish a connection model dialogue CNMD, The references/signals mentioned earlier are such parameters which e.g. contain such information which points out unique port objects and which are necessary to carry out certain procedures e.g. association between two connection models in adjacent processes. When CNMD has been established, address information and desired condition of the connection (reserved or through- connected) will be transferred onto CNMD without the service controlling functions being effected or involved. The connection model requires that there is a connection set up function CSF which upon request can interconnect two points in the internal switching network. The interface towards this connection set up function is independent of what this network looks like and how many switches there are in same. • As apparent from Fig. 4, the connection set up function has two dialogues, namely a dialogue CSFOD on the originating side where the connection is requested, and a dialogue CSFTD on the terminating side where the result is commu¬ nicated. For details about how these dialogues are used, reference is made to the appended arrow diagram. • The connection set up function CSF does not have to be executed in only one process but can be divided onto several processes with internal protocols therebetween if the network through which the connection is to be set up, is physically distributed. However, it is essen¬ tial that the structure with the two dialogues CSFOD and CSFTD is maintained. • In accordance with the example, two processes are to set up a common connection. The two service controlling func¬ tions using the connection model are called OC (Origina¬ ting Call) and TC (Terminating Call) . • The connection model objects are denoted with an O and a T, respectively, at the end in order to show in which process they are. • The communication between the service controlling functions and the connection model objects is carried out by so cal- led method calls with direct answers. Moreover, notifica¬ tions or "events" will be communicated to the user by the model e.g. when the through-connection is ready. • The arrow diagram illustrates set up, through-connection in two steps, and release. Above the example according to Fig. 4 which illustrates the simplest case, the model contains support for redirecting an already established connection, a possibility to prepare two connections to the same access point and then choose between those, and finally handling of connection-related data (accu¬ mulated delay, echo cancellation information etc) . As apparent from Fig. 4, two processes OC and TC, respective¬ ly, are to set up a common connection. The physical connec¬ tion which is to be set up is a connection between two sub¬ scribers A and B. A connection model according to the inven¬ tion comprises a set of connection objects ConnO, ConnT and port objects PortO, PortT, EndPortO and EndPortT related to each other by association or preliminary association. An ab¬ stract connection is a set of connection objects and port objects associated to each other to form a chain. The chain is terminated by a port object in each end. These two ends represent contact possibilities to physical access points. The subsequent arrow diagram which comprises 11 pages illu¬ strates an example on the implementation of the method accor¬ ding to the invention which means that the signal exchange is illustrated for bringing about set up, through-connection and release of a connection. The arrows and the levels in the arrow diagram point out in which order and in which direction the signalling takes place to bring about the desired actua¬ tion of the different objects. To get a good understanding of the processes, the description of the events is written into a table alongside the direct course of events which is indi¬ cated by arrows. All originating functions are marked with an O and all terminating functions are marked with a T. SET-UP, THROUGH-CONNECTION AND RELEASE DESCRIPTION INTERWORK OC ConnO CSF ConnT TC EndPoreo ι Porto PortT EndPortT Starting conditions: OC and TC exist and are communicating with each other.Each has seized one access point. OC creates its connection objects: EndPortO is created with a create TP agent as input data. The TP agent contains the address to an access point. Connection objects are create created with connection dat (band width, type of connec¬ tion) as input data and in¬ formation about routing di¬ rection upon setting up of create the connection. PortO is created. The connection objects with¬ in the originating proces_s are associated together: associa Associate ConnO with PortO. associate Associate ConnO with associate DESCRIPTION INTERWORK OC ConnO CSF ConnT TC EndPortO PortO i PortT ι EndPortT To obtain a connection it is necessary that the con¬ getPort nection models are associated: OC requests a communicqation port identity from PortO; sendPortld this port identity is sent over to TC (via TSD). associate associat* The port identity is sent to associate PortT with getPortld PortO. 'i sendPor .id OC requests a communication port identity from PortT; this port identity is sent over to OC (via TSD). associa The port identity is sent to PortO to associate PortO associate with PortT. CNMD is now established between PortO and PortT. Information about the res¬ TPagentlψfo pective access point is sent >| TPagentIn to between the connection models TPagentln DESCRIPTION INTERWORK OC ConnO CSF ConnT TC EndPortO PortO PortT i EndPortT releaselnfo releaslAfo The association between ConnO and EndPortO is removeAisociatiφn removed. removeAέsociatiφn The association between ConnO and PortO is removed. removeA socia iφn removeAisociatioA The association from PortO to PortT is removed. removeAssociatiφn removeAs ociation The association between ConnT and EndPortT is removeAssφciation removed. removeAssφciation The association between ConnT and PortT is removed. removeAssφciation removeAssφciation The association from PortT to PortO is removed. removeAssφciation

Claims: CLAIMS 1. Telecommunication network comprising digital computer con- trolled telephone exchanges and subscribers connected there¬ to, wherein the control of the handling of connections bet¬ ween subscribers in the network is distributed out in the network, characterized in that in an object oriented system, a plurality of different, mutually independent processes are arranged in such a manner that one or more of said processes under control of one or more processors are adapted to con¬ trol the handling of that or those connections which are ne¬ cessary to achieve e.g. reservation of a connetion path, con¬ nection set up, through connection and release of a complete connection between subscribers or nodes in the network, and redirection of connections, wherein abstract connection paths are adapted to be set up by means of connection models in which different types of objects, e.g. connection objects, port objects and end port objects, are linked together, said linking being carried out by means of association or prelimi¬ nary association, wherein upon association of connection mo¬ dels, references in the form of signals exit from a port in a first connection model to a port in a second connection mo¬ del, and that upon internal association within a connection model, references are supplied between adjacent connection objects and port objects, and that upon a set-up abstract connection between two end ports and between those associated connection objects, port objects and connection models, a physical connection is adapted to be set up by exchanging references between abstract and physical access points, and that upon preliminary association, it is possible to associa¬ te a further access point from the same end port above a con¬ nection set up by normal association. 2. Telecommunication network according to claim 1, characte¬ rized in that each user (process) can control and change a connection without any coordination with other users (proces¬ ses) and without any knowledge of the topology of the network . 3. Telecommunication network according to claim 2, characte¬ rized in that more than one connection model can be included in a connection path. 4. Telecommunication network according to claim 1, characte¬ rized in that said ports and connection objects are made up of callable objects in a connection model. 5. Telecommunication network according to claim 1, characte¬ rized in that said objects are made up of abstract counter¬ parts to physically definable conceptions. 6. Telecommunication network according to claim 1, characte¬ rized in that a physical connection can not be established until an abstract connection is set-up in full in a chain. 7. Telecommunication network according to claim 1, characte- rized in that said processes are user related. 8. Telecommunication network according to claim 1, characte¬ rized in that said redirection of connections imply associa¬ ting a new access point to an end object.

Inventors: OLA DAGBERG LARS JOHN, TOMAS AURELL KARL STURE, OLA, DAGBERG, LARS, JOHN, TOMAS, AURELL, KARL, STURE
Applicants: ERICSSON TELEFON AB L M, TELEFONAKTIEBOLAGET L M ERICSSON
Application year: 1995
Main classification: H04Q3
IPC codes: G06F9, H04M3, H04Q3