Method of integrating a packet network in a communications system

The invention relates to a method and an arrangement for Integration of a packet-oriented network in a communication system.

Modern communication systems are by coalescence characterized by information and communication infrastructures. Here, communication systems are known which a voice and / or video communication over packet-oriented Networks support. Such a process is in the art mostly with the overall concept of 'Voice over IP 'or abbreviation' VoIP 'designated by the abbreviation' IP ' for 'Internet Protocol', a commonly used protocol is to exchange data over packet-oriented networks. For VoIP communications are the protocols H.323 or SIP (Session Initiation Protocol) widely.

SIP is a signaling protocol for Internet telephony as well as other services such as conference interactions, event notification, Messaging etc. This protocol was developed by the working group MMUSIC (Multiparty Multimedia Session Control) working group IETF (Internet Engineering Task Force). The H.323 standard is a international ITU-T (International Telecommunication Union - Telecommunications Standardization Sector) for voice, data and video communication over packet-switched Networks.

Besides an infrastructure for exchanging packet-oriented data is a telephony infrastructure with dedicated Leads to communication terminals to be widespread. For economic and safety Reasons therefore in many communication systems do not fully permanent change to a pure packet-oriented architecture provided. Instead, existing communication systems with a telephony infrastructure of dedicated base Lines to devices for connecting communication terminals based on a packet-oriented network extended. Such communication systems are therefore often called 'convergent' communication systems, which refers to a combination of the two infrastructures becomes.

A control of the communications terminals is effected in communication systems with a telephony infrastructure based of dedicated lines by a central communication device.

The central communication device provides performance available and performs switching between communication system-internal or -external communications terminals by.

In architecture purely packet-oriented VoIP communication systems is a central switching and control however, no provision of communication partners, instead which is carried out the placement and performance feature control in pure VoIP communication systems locally in the Communication terminals or in distributed master computer.

To complete integration of VoIP-based communication terminals is in a converged communications system therefore a mere bilateral conversion of packet-oriented and continuous-time payload - ie voice or Video data - not enough. A convergent communication system also requires a conversion of signaling information between the two infrastructures. Signaling information contains data for connection control, Signaling etc.

In 'classic' - ie central, for example, according to the principle of a Time multiplex between communication terminals with dedicated Lines promoting - communication equipment Communication device is for example the signaling protocol 'DSS1' known. The DSS1 protocol ( 'Digital Subscriber System No. 1') is an ITU-T 1411 ( 'International Telecommunication Union') based European ISDN protocol ( 'Integrated Services Digital Network') for the signaling channel of the European Euro-ISDN.

In modern communication systems, contain signaling information Moreover, enhanced features supporting Data, for example to display a name and other information a calling or called subscriber to a Communication terminal.

With a use of - the skilled person as a 'gateway' known - expansion modules for 'classic' communications equipment to connect VoIP communication terminals is currently not the whole feature spectrum both on the wireline as well as to the VoIP communication terminals available.

The object of the invention to provide means, in their application integration of a packet-oriented network in a communication system with a central communication device is provided, wherein both the central communication device assigned as the packet-oriented network Communication terminals have an identical feature configuration should have.

An object is achieved with regard to their method aspect by a method comprising the features of claim 1 and with respect to their device aspect an arrangement having the features of claim 20th

According to the invention is to integrate a packet-oriented Network to a through a central communication device controlled communication system, a gateway and a Kommunikationsleitrechner used. is done by the Gateway a reciprocal implementation of signaling and Payload of the central communication device in decentralized Signaling and Nutzdatendiensten exchanged Data. This decentralized signaling and Nutzdatendiensten come in via the distributed packet-oriented network Kommunikationsleitrechnern for execution. In a with an application interface of the central communication device connected host computer, communication data This application interface in the Kommunikationsleitrechner processable state information implemented.

is an essential advantage of the method according to the invention to see that from the reciprocal reaction Communication data of the application interface and the packet-oriented Network transmitted status information for all communication terminals in the communication system a is uniform feature design available.

In this way, for example, a notification of having the packet-oriented network-connected VoIP communication terminal (Voice over Internet Protocol) at the central Communication device as practicable, under exclusive Use a Gateway can not be realized. The gateway can function show only a reciprocal Implementation of packet-oriented signaling and evaluable user data in the central communication device carry signaling and user data, the exchanged with the central communication device not signaling data for the control and signaling all functions and features offered sufficient.

Vorteilig is further that the realization of the invention Solution an interface for exchange of communication data is used with a computer system, which in the form of an application interface in many central Communication devices is realized. A structural is reshaping the central communication device thus the realization of the inventive method is not necessary.

Advantageous further developments of the invention are in the dependent claims indicated.

Advantageously, is for data in packet-oriented Network between decentralized signaling and Nutzdatendiensten be replaced, the widespread SIP (Session Initiation Protocol). to Definition of the structure and layout of exchanged data is for example in accordance with the SIP protocol, the electronic Form published document Handley, M. et al .: 'SIP: Session Initiation Protocol ', Network Working Group (ed.), Request for Comments: 2543, March 1999 to be used.

Advantageously, is to communicate with the application interface the widespread standard CSTA (Computer Supported Telephony Applications) used. CSTA is a standard of ECMA (European Computer Manufacturers Association) for computer-aided telecommunications applications for linking computer systems and telephony devices. This coupling is in professional circles with 'computer Telephony Integration, CTI abbreviation refers. The standard CSTA defines the structure and nature of the messages for the various service features fixed. It concerns with CSTA that is to say no interface specified, but rather a guide to standardized implementation of a CTI functionality. As examples of the standards-compliant Implementation are the programming interfaces TSAPI and TAPI mentioned, which build on the CSTA definitions.

To define the structure and layout of exchanged Communication data in accordance with the standards CSTA are eg following published in electronic form documents - Publisher respectively the 'ECMA Technical Committee' - be applied:<ul><li>ECMA-179, June 1992 'Services for Computer Supported Telecommunications Applications (CSTA) Phase I ';</li><li>ECMA-180, June 1992, 'Protocol for Computer Supported Telecommunications Applications (CSTA) Phase I '</li></ul>

These documents relate to a designated 'Phase 1' Publication status, which possibly also other documents according to the publication stalls available at the filing date 'Phase 2' and 'Phase 3' are applicable.

An exemplary embodiment with further advantages and embodiments of the invention with reference to the drawing explained in more detail.

They show:<dl tsize="20"><dt>Fig. 1:</dt><dd>a structural diagram for the schematic representation of a Communication system;</dd><dt>Fig. 2:</dt><dd>a structural diagram for the schematic representation of a Exchange of control messages in a communication system for the transmission of voice data;</dd><dt>Fig. 3:</dt><dd>a chronological flowchart for schematic Representation of an exchange of control messages for Realization of an evaluation of call data of a participant;</dd><dt>FIG. 4A to FIG. 4C:</dt><dd> a chronological flowchart with a schematic Representation of a control message exchange for realizing a call signaling throughout Communication system;</dd><dt>Fig. 5:</dt><dd>a chronological flowchart with a schematic Representation of a control message exchange to implement a communication system-wide Availability information of a subscriber;</dd><dt>Fig. 6:</dt><dd>a chronological flowchart with a schematic Representation of a control message exchange to implement a communication system-wide Availability information of a subscriber in a row a failure of a communication terminal; and</dd><dt>Fig. 7:</dt><dd>a chronological flowchart with a schematic Representation of a synchronization of control data.</dd></dl>

In Fig. 1, a communication system is shown CSY. The Communication system CSY is a central communication device PBX controlled. This central communication device PBX is in alternative embodiments as an Enriched in the usual way - not shown - Communication device composite realized. In the aforementioned embodiment controls each central communication device PBX in communication device composite a subsystem CSY of the communication device composite managed - not shown - overall communication system.

The central communication device PBX is as according to a timeslot-oriented switching method - in the Experts often as 'Time Division Multiplex', TDM - configured. Control via signaling data and an exchange of user data - for example, voice and / or Video data - from the central communication device PBX connected communication terminals, here the first communication terminal KE1 is done, for example, using the ISDN protocol ( 'Integrated Services Digital Network').

The central communication device PBX has a EXT interface for expansion modules, via the signaling and payload with these expansion modules be replaced. done with an ISDN protocol the exchange of useful information in a conventional manner over a so-called B channel, while the exchange of signaling information takes place via a separate D-channel.

The central communication device PBX has further an application interface APIF by which a Communication of the central communication device PBX with running computer system - on a - not shown Telephony functions supporting applications occurs. An example of such - not shown - Applications are so-called business applications ( 'Business Applications') which often to integrate telephony functions in a multiple agent of a so-called 'call center' used distributed customer request processing system will. The business application exchanges this with the central communication device PBX call control and Monitoring information from, which is usually in the art as' Call-Control 'or' Monitoring' information be referred

About a packet-oriented network LAN are several communication terminals - In the drawing is an example only a second communication terminal KE 2 shown - on Based on a packet-oriented communication - even VoIP (Voice over Internet Protocol) - interconnected.

As signaling protocol is the embodiment of the 'Session Initiation Protocol', just use SIP. It deals This is a modular protocol that a Call signaling, localization and registration of Communication terminals supported. The invention A process is moreover independent of the choice of a particular Communication or signaling protocol and Therefore as well as a signaling protocol in accordance with the ITU-T standard H.323 can be used.

The second communication terminal KE 2 exchanges packet-oriented Data with a corresponding communication partner or performing with control functions Kommunikationsleitrechnern PRSRV, APSRV, Server RGSRV from.

A location of a subscriber is a Lokalisierungsleitrechner PRSRV controlled. The Lokalisierungsleitrechner is in the art also with 'Presence and Availability Server 'designated. The Location Server PRSRV done a management of available participants, and which subscriber when and how can be reached. These Administration takes place in the form of a notification to applications, the other SIP-F unktionalitäten support.

Derlei applications are, for example, on a Applikationsleitrechner APSRV or 'Application Server' for execution brought. The supported Applikationsleitrechner APSRV Moreover, video and audio conferencing, and controls or registered - in cooperation with the Lokalisierungsleitrechner PRSRV - the availability of a participant. The Applikationsleitrechner APSRV cooperates for this purpose occasionally with so-called 'Basic clients', ie the employer available computer systems - in other - not shown are.

The Registration Server RGSRV - often perceived as' Registration and Proxy Server designated '- controls a registration a SIP subscriber and causes optionally a route guidance of a call to durchzustellenden the registered subscriber for the communication terminal KE2.

To support operational and administrative mediation and feature functions and to support of maintenance functions is the VoIP communication system LAN associated with a database DB which in the art often as OAM database (Operation, Administration and Maintenance) is referred to.

The packet-oriented network LAN comprises a so - hereinafter VoIP communication system LAN-called - communication subsystem, in which a switching and feature control decentralized, i.e. distributed in VoIP communications terminals as the second communication terminal KE2 and with decentralized Kommunikationsleitrechnern PRSRV, APSRV, Server RGSRV done. This VoIP communication system LAN is inventive with the central Communication device PBX connected.

The connection of the VoIP communication system LAN via one at the application interface APIF of the central Communication device PBX connected host computer SIPSRV and an interface to the EXT central Communication device PBX connected Gateway GW. The master computer SIPSRV and the gateway GW are the VoIP communication system LAN about - not shown - Network interfaces connected.

In the following, with further reference to the functional units of FIG. 1, an exchange of control data in the communication system CSY explained in more detail.

Fig. 2 shows a subset of already from Fig. 1 the known Components of the communication system CSY. With reference to FIG. 2 an exchange of control data is shown in the following.

There is first a process for registering a subscriber represented in the VoIP communication system LAN. On User Answers on the central of the communication device PBX managed first communication terminal KE1 by entering a personal identification number, PIN on.

A registration of the subscriber in the VoIP communication system LAN serves, for example, incoming to the subscriber Calls to a VoIP communication terminal such as the to ignore or send second communication terminal.

For purposes of this registry, an evaluation of Communication data of the application interface APIF and generation of a force in the VoIP communication system LAN Registration message. According to the configuration of the in VoIP communication system LAN configured signaling protocol SIP corresponds to this registration message a for registration purposes Enriched SIP message. at the generation of the registration message by the Application interface APIF communicating host SIPSRV done an implementation of the PIN functionality to the Registration message. The recipient of this registration message in the VoIP communication system LAN is for example the Registration Server RGSRV.

The application interface APIF example for bidirectional exchange of communication data in accordance with the protocol CSTA (Computer Supported Telephony Applications) provided. The inventive process is moreover on - the embodiment not shown - alternative Communication protocols for exchanging communication tion data of the central communication device PBX with a - not shown - computer system applicable.

A registration of the subscriber to the central communication device PBX by entering an assigned PIN on the first communication terminal KE 1. The communications terminal KE1 this subscriber is then through the assigned to the central communication device PBX. The assignment the identified by their PIN participant for the first Communication terminal KE 1 is the application interface APIF with a CSTA event message EVT 1 to the master computer SIPSRV reported. This CSTA event message EVT 1 is referred to in the art also with 'Mobile User Activate', wherein the attribute 'mobile' expresses that the subscriber at one in the communication system CSY can log largely arbitrary communication terminal.

The of the event message EVT to the host computer SIPSRV transmitted data include for example the PIN for identification the subscriber and an identification of the associated with the subscriber first communication terminal KE1. The identification of the first communication terminal KE1 for example, by specifying the (PABX) Call this communication terminal KE 1, which in professional circles is often also referred to as 'extension'.

The host now has the task, from the PIN and the extension - In Figure 2 abbreviated with 'Ext.'. called - a Registration message REG to register a SIP participant - 'SIP User' - to produce. For this purpose, the master computer SIPSRV a database query to the database DB QUE triggered. The Database contains a data file to associate a SIP participant the PIN of the subscriber. The result of this query QUE is transmitted to the host computer SIPSRV. For example is in this way a PIN of content '45898' allocated to a text listing of the contents 'Christian', which characterizes the SIP subscribers. In addition, he follows for a mobile subscriber a write access to a Database the database DB, through which the currently logged Extension of the subscriber in the form of the extension number - Extension - the communication entry KE1 in a Database the database DB is entered.

With the help of the SIP participants characterizing text entry - 'Christian' - is from the master computer SIPSRV a registration message REG generated and to the Registration Server RGSRV sent. The registration message REG contains a piece of information, for example, the text content 'Register: christian@sip.com' and 'Contact: 45898@sip.com '.

With the help of a further information field in the database entries the database DB is a call forwarding or call forwarding adjustable by the VoIP communication system LAN. Such an information field includes, for example, the identification number of the communication terminal, are to be diverted to the incoming calls.

Such call transfer or diversion is in the form one offered by central communication devices PBX Feature known and is at one with this connected communication device KE 1 by entering a Control command causes. The advantage of a Forward set up or diversion via the VoIP communication system LAN, lies in the fact that the associated packet-oriented Network LAN access from widely taut information networks such as the so-called - not shown - Enables Internet. A network access provided is a participant from almost every point of possible by means of a so-called SIP clients - for example, a portable computer unit - a diversion of his communication terminal KE1 to another forwarding destination, for example, the second communication terminal KE 2 to cause. The forwarding destination can also use an the central Communication device PBX assigned - not shown - His communication terminal.

The following shows how the further processing an incoming call to a central both to the communication device PBX and in the VoIP communication system, especially in the Registration Server RGSRV, registered Participants carried out.

At the Lokalisierungsleitrechner PRSRV meet a call signaling CLL in the form of a SIP message. This call signaling either from the VoIP communication system LAN or was in the form of a CSTA message via the application interface APIF of the central communication device PBX based. In the first case, the origin of the incoming call a - not shown - communication terminal within the VoIP communication system LAN, in second case, a - not shown - the central communication device associated communication terminal.

The Lokalisierungsleitrechner PRSRV determines to which communication terminal the incoming call can be put through should. The Lokalisierungsleitrechner PRSRV used for this purpose from the database DB on the Registration Server RGSRV to relating information. Depending on a specific reference to the Information specific configuration of the subscriber then one from Lokalisierungsleitrechner PRSRV or more Invitation message INV1, INV2 produced and shipped. A first invitation message INV 1 is a Rufdurchstellung determined on the first communication terminal KE 1, according to a second invitation message INV 2 for the second communication terminal KE 2. The last-mentioned second Invitation message INV2 is sent directly to the second communication terminal KE2 through.

The second invitation message INV 2 contains a piece of information For example, the text content 'Invite: christi an@sip.com ', according to the' address' of the participant in VoIP communication system LAN.

The first invitation message INV 1 contains an information part For example, the text content 'Invite: 45898@sip.com ', according to the identification number of the Participant in the central communication device PBX. This first invitation message INV 1 is via the gateway in adapted to the central communication device PBX Signaling message SETP implemented. Such signaling message SETP corresponds for example to the DSS1 protocol and contains a piece of information, for example, a so-called setup command.

In the following, a method will be explained, with its implementation another common feature configuration in the VoIP communication system LAN as well as in that of the central communication device PBX managed - in the Drawing only by the first communication terminal KE1 represented - communication network is made possible.

Many central communication devices support called her Outbox function. In a 'letter box' are Callback requests and messages from callers stored. At the Communication terminal KE 1 is a callback request or Presence of a message to the associated subscriber, eg signaled by a visual indication.

To achieve this feature in the entire communication system CSY is as in the previous versions a first subscriber in Registrierungsleitrechner Server RGSRV the VoIP communication system LAN registered. the first party is the first communication terminal KE 1 assigned. Now Enables a second user, the mailbox feature for the first participant, for example by the Feature 'Please call' is activated, the first communication terminal KE 1 signaling an a 'Message waiting', in the art with 'Message Waiting Indication 'or MWI abbreviation referred.

For the transmission of this MWI is in the master computer a SIPSRV implemented routine, which one at discrete time intervals Interrogation of MWI states via the application interface APIF performing on the central communication device. Such query is in the art as 'polling' designated. Such polling operation is performed repeatedly by a CSTA request message 'getMessageWaitingIndicator' calling routine in the master computer SIPSRV eg in a time interval of one minute. The arguments of the CSTA request message are a communication terminal KE1 characteristic identification. The CSTA Answer message contains a Boolean parameter of a indicates message waiting or not. If a waiting Message before, it is in an information field of the response message sent to the host computer SIPSRV that this revalues ​​in a SIP message to the first and for the Participants in the VoIP communication system LAN registered communication terminal KE2 passes.

The advantage of this method is that the first Users now also receives messages if he does not at his first communication terminal KE 1 is. The second for him registered communication terminal KE 2 is, for example as mobile communication unit KE2, for example in the form of a PDA ( 'Personal digital assistant') configured.

In the following Figures 3 to 7 are each a chronological Flow diagram for the schematic representation of a control message exchange between system units of the communication system CSY shown. Between the system units exchanged control messages, usually in the form of request messages ( 'Request') or confirmation messages ( 'Confirm') are in dependence of certain out convicted or be executed actions or events have occurred triggered in the system units.

Fig. 3 shows a chronological flowchart with a schematic Representing an exchange of control messages between system units of the communication system CSY.

Time lines 1,2,3,4 and 5 are the in this order first communication terminal KE 1, the central communication device PBX, the application interface APIF, the assigned host SIPSRV and the database DB. The Time lines 1,2,3,4 and 5 run from top to bottom, so that later times lie further down than earlier points in time.

With the below on the basis of control messages exchanged The method shown is a logging Connection or call data for the communication system achieved CSY registered participants. Such logging is usually carried out in - not shown - Control units of the central communication device PBX for their assigned communication terminals KE1, but are not in computer units such as the Applikationsleitrechner APSRV available in the VoIP communication system LAN or evaluated. The following procedure is a transmission of connection or call data in the designed as a packet-oriented network VoIP communication system LAN achieved with usual technical by Ability to access the packet-oriented network LAN under Inclusion globally networked networks is achieved. done The storage of connection or call data eg with records of the form Participant, call type, Start time of the call, call duration, Associated participants'. Depending on the data protection regulations, a Record shall be reduced by a few pieces of information. The Records after a successful - explained below - Transmission of the central communication input direction PBX to the master computer SIPSRV in the database DB stored.

At the time t0 for answer on his first Communication terminal to KE1. A registration that has is in the form of an event message 110 from communication terminal reported KE 1 to the central communication device PBX, which normally referred to as a 'SETUP' message 110 becomes.

At time t1, received the central communication device PBX an event message 112 to the communications terminal KE1 which signaling an incoming transmitted and times usual reputation as 'ALERTING' message referred 112th

At time t2, received the central communication device PBX an event message 114 to the first communication terminal KE1 which a call has been setup reports to the communication terminal KE 1 and customary in the art also is referred to as 'CONNECT' message 114th

About the application interface APIF this is done Establishing a connection from the central communication device PBX along with other parameters - such as the subscriber number the calling subscriber, the connection type, etc. - connected in the form of a CSTA event message 116 also to the Host SIPSRV reported. This at the time t3 sent event message 116 is conventional in the art as 'CSTA_ESTABLISHED_EVENT' designated. The master computer SIPSRV stores the additionally sent call data and tracked in a furnished for this connection process the state of this connection.

At time t4, the first communication terminal received an event message 118 to the central communication device PBX which announces a call has been degradation and normally referred to as a 'DISCONNECT' message 118 becomes.

About the application interface APIF this is done Disconnection from the central communication device PBX along with other parameters in the form of a CSTA event message 120 also connected to the host computer SIPSRV reported. This time t5 sent event message 120 is conventional in the art as 'CSTA_CONNECTION_CLEARED_EVENT' designated. The master computer SIPSRV stores the additionally sent call data and followed in a furnished for this connection Process the state of this connection.

The master computer SIPSRV stores the addition mitgesandten Call data and ends the setup for that connection Process of generation of a call record, which at the time t6 in an information field a write access request is sent 122 to the database DB becomes.

4A, 4B, 4C again show a chronological flowchart with a schematic representation of an exchange control messages between system units of the communication system CSY. This exchange of control messages is a transfer of at the central communication device incoming connection requests to the VoIP communication system LAN. The associated method is based on the control messages exchanged explained.

Time lines 1,2,3,4 and 6 are the in this order first communication terminal KE 1, the central communication device PBX, the application interface APIF, the Host SIPSRV and the Lokalisierungsleitrechner PRSRV assigned. In Fig. 4C is another, the gateway GW associated Beam 6 and a time the second communication terminal KE2 associated timeline 8 shown.

With the method described below is met, that an incoming call on which the central communication device PBX associated communication terminal KE 1 also to the VoIP communication system LAN to another, registered for the subscriber communication terminal KE 2 being passed over. In the reverse - not shown here - Direction, ie, a reconciliation from the VoIP communication system LAN associated communication terminal KE2 to the first communication terminal KE 1 is that reconciliation controlled by the gateway GW.

At the time t0 for answer on his first Communication terminal to KE1. A registration that has is in the form of an event message 210 from communication terminal reported KE 1 to the central communication device PBX, which normally referred to as a 'SETUP' message 210 becomes.

At time t1, received the central communication device PBX an event message 212 to the communications terminal KE1 which signaling an incoming transmitted and times usual reputation as 'ALERTING' message referred 212th

About the application interface APIF the call signaling from the central communication device PBX in connected form of a CSTA event message 214 also to the Host SIPSRV reported. This sent at the time t3 Event message 116 is conventional in the art as 'CSTA_DELIVERED_EVENT' designated.

At time t3, the master computer SIPSRV received an invitation message 216 to the Lokalisierungsleitrechner PRSRV, which is also referred to as' INVITE' message. The Lokalisierungsleitrechner PRSRV determined in a database - For example, in an internal data not shown Bank or in the central database DB - from the Information invitation message 216 contained on the Participants, whether this account in the VoIP communication system LAN and whether this there associated with a communication terminal is. The Lokalisierungsleitrechner PRSRV sends an allocation of communication terminals a - not illustrated - invitation message to each of these communication terminals. One of the participants in the VoIP communication system LAN associated communication terminals is For example, the second communication terminal KE 2.

The other method is divided into two cases. In the first Case - see Figure 4B -.. By the participant the conversation the first communication terminal KE 1 contrary, in the second Case - see Figure 4C -.. Takes the participants on the call second communication terminal KE2 contrary.

Fig. 4B is a continuation of the chronological flowchart exchanged control messages with an answer the subscriber in which the central communication device PBX assigned first communication terminal KE 1.

At the time t4 transmitted the central communication device PBX an event message 218 to the first communication terminal KE1 which a call has been setup reports to the communication terminal KE 1 and customary in the art also is referred to as 'CONNECT' message 218th

About the application interface APIF this is done Establishing a connection from the central communication device PBX in the form of a CSTA event message 220 also to the connected Host SIPSRV reported. This at the time t5 sent event message 220 is conventional in the art also referred to as 'CSTA_ESTABLISHED_EVENT'.

The task of the host computer SIPSRV now is that Call signaling in the VoIP communication system LAN the participants registered communication terminals KE2 to end.

At time t6, the control computer transmits this SIPSRV a termination message 222 to the Lokalisierungsleitrechner PRSRV, which is also referred to as a 'Cancel message. The Lokalisierungsleitrechner PRSRV determined in a database from information contained in the abort message 222 information about the participants who call signaling in which associated with the subscriber in the VoIP communication system LAN Communication terminals KE2 is quit. The Lokalisierungsleitrechner PRSRV sends to this investigation a - Not shown - abort message to each of these communication terminals KE2.

Fig. 4C shows a continuation of the chronological flowchart exchanged control messages with an answer the subscriber in the VoIP communication system LAN associated second communication terminal KE 2.

After receipt of the communication link at second communication terminal transmits the second communication terminal KE2 time t4 an event message 224 to the Kommunikationsleitrechner SIPSRV which this a call has been building reports and expert also common is referred to as 'CONNECT' message 224th

In the following, first, a first communication link between the host and the second communication terminal SIPSRV built up. The master computer SIPSRV building addition a second communication connection to the the assigned subscriber to the central communication device PBX the first communication terminal KE 1 on while the first communication link is maintained. In the course of a so-called 'multi-step transfers' are the two communication links then connected, so that the subscriber Finally, on the second communication terminal KE 2 to the ers th communication terminal KE1 accept incoming call can.

For purposes of an illustrative representation of a transfer of Communication link is shown in FIG. 4C, the first communication terminal a KE1 assigned timeline 1 introduced.

In view of the above it should be noted that an exchange of not having control, signaling or user data the actual communication terminal KE 1 is done, but manage rather a communication terminal KE1 Instance in the central communication device PBX. The representation of two time lines 1,2 for the instance of first communication terminal KE 1 in the central communication device PBX and for the central communication device PBX itself has the purpose of distinction. A structure of the communication connection takes place with the Instance of the first communication terminal KE 1 while central communication device PBX itself for control is the communication link responsible.

The host sends via the application interface APIF time t5 a CSTA request message 226 to the central communication device PBX, a redirection the communication link requests. This request message 226 is conventional in the art as 'CSTA_DEFLECT_CALL_REQUEST' designated. A presentation related Crossing of the request message 226 with the Timeline 7 of the gateway GW is not to be seen in the way that the request message 226, the gateway GW realiter happens.

The exchanges instance of the first communication device KE1 with the master computer SIPSRV then useful, signaling or control messages from which the structure of the communication link concern and which of the skilled worker the DSS1 Specifications 'Supplementary Services' or the 'SIP Recommendations' for a transfer of communication links are common. The structure of the communication link is in the drawing with a shaded block shown. For the data exchange it is the gateway GW used.

After the first communication connection between the instance the first communication device and the host computer KE1 constructed SIPSRV confirmed at time t6 the two partners of the communication link to each other the successful development by a - in the drawing shown as a zweipfeilige connection - confirmation message pair 228th

The aforementioned second - in the drawing with a hatched block shown - communication link between the second communication terminal KE 2 and the instance the first communication terminal is carried out according to the Replacing the confirmation message pair 228 set, said second communication link in analogue Manner with a - in the drawing as a zweipfeilige Compound represented - confirmation message pair 230 is confirmed. The redirection to the second communication terminal KE2 is done with it.

In Fig. 5 is a chronological flowchart with a schematic Representation of an exchange of control messages for Implementation of a communication system-wide availability information a participant shown.

The background of the method described below is, that assigned to the central communication device PBX Terminal KE1 registered participants, which at This communication terminal KE 1 active on a call, registered as 'not available' in the VoIP communication system LAN shall be. This condition is caused by a non-availability of information - 'Busy information' or 'Off Hook Condition '- of the central communication device reported PBX to the VoIP communication system LAN to a calling party from the VoIP communication system LAN via to inform the unavailability of the called subscriber.

One questioned before establishing a connection unavailability information further causes the line is busy the first communication terminal KE 1 communication link between the calling subscriber in the VoIP communication system LAN via the gateway GW and the central communication device PBX to the first communication terminal KE 1 is constructed. This measure therefore results in a advantageous savings in network bandwidth.

The process is in turn based exchanged control messages described. Time lines 1,2,3,4 and 8 are in this Ranked the first communication terminal KE 1, the central communication device PBX, the application interface APIF, the host computer and the SIPSRV Registrierungsleitrechner assigned Server RGSRV. Time lines 1,2,3,4 and 8 extend from top to bottom, so that later Instants lie further down than earlier points in time.

The first participant raises his first communication terminal KE1 the handset or occupied on a software application KE1 an assigned line resource. At the time t0 is this event from the first communication terminal KE 1 the central communication device PBX in the form of an event message 310 received.

The event of lifting by the subscriber will continue at the time t1 from the central communication device PBX via the application interface APIF to the host computer SIPSRV reported in the form of an event message 312th These CSTA event message 312 is conventional in the art as 'SERVICE_INIT_EVENT' designated.

The master computer SIPSRV receives the event message 312 and manipulates. At the time t2 sends the master computer a request message 314 to the Registration Server RGSRV - 'SIP Registrar' - the cancellation of a Communication terminal in data sets of the Registration Server RGSRV initiates. The request message 314 is normally referred to as' register-mode object 314 and has the Registration Server RGSRV by on the value zero (0) adjusted, so-called 'EXPIRE' argument a cancellation or deregistration of the first communication terminal KE 1 to.

The Registration Server RGSRV takes after receipt of Request message 314 towards a change in the Communication terminal KE1 before data sets reserved, now recorded as a consequence of this as 'not available' becomes.

After - in the drawing by a dotted line illustrated - the period during which the participants in the communication terminal KE1 an active communication link has, ended this connection as the laying on of the Listener.

At time t3, this event is from the first communication terminal KE 1 to the central communication device PBX transmitted in the form of an event message 316th

This event is time t4 of the central communication device PBX via the application interface APIF to the host computer SIPSRV in the form of an event message 318 reported. This CSTA event message 318 is normally referred to as 'CONNECT_CLEARED_EVENT'.

The master computer SIPSRV receives the event message 318 and manipulates. At the time t5 sends Leit computer SIPSRV a request message 320 to the Registration Server RGSRV that a cancellation of the communication terminal KE 1 in data sets Registrierungsleitrechner Server RGSRV initiates. The request message 320 is conventional in the art also referred to as' register-mode object 320 and has the Registration Server RGSRV by a value greater than zero (0) adjusted, so-called 'EXPIRE' argument an application or registration of the first communication terminal KE 1 to.

The Registration Server RGSRV takes after receipt of Request message 320 towards a change in the Communication terminal KE1 before data sets reserved, the consequence of this is now flagged as 'available'.

In Fig. 6 is a 5 to Fig largely analogous method to. a chronological flowchart with a schematic representation an exchange of control messages for implementation a communication system-wide availability information a participant shown. In contrast to procedures FIG. 5 is based unavailability or availability the participant in the process shown now is that the subscriber associated first communication terminal KE1 goes out of operation or put back into operation becomes. An out-of-state, for example by Pull the plug connection between the communication terminal KE 1 and a communication terminal KE1 with the connecting end central communication device PBX - Not shown - with cable junction box caused.

An inoperative walking the first communication terminal KE1 at time t0 with an event message 410 from the central communication device PBX via the application interface APIF to the host computer SIPSRV. This CSTA event message 410 is conventional in the art as 'OutOfService event' called.

The cancellation of the communication terminal KE 1 is analogous the reference to FIG. 5 illustrated embodiment, wherein the local control messages 314 and 320 in FIG. 6 Control messages 412 and 416 shown correspond.

A restart of the first communication terminal KE 1 at time t2 with an event message of 414 the central communication device PBX via the application interface APIF to the host computer SIPSRV. This CSTA event message 414 is conventional in the art as 'BackInService event' called.

In Fig. 7 is a chronological flowchart with a schematic Representation of an exchange of control messages for Implementation of a communication system-wide synchronization shown.

The synchronization mentioned has the following background: Joined a participant at his, the central communication device assigned to the first communication terminal KE1, he also provides - by means of the aforementioned Process takes place - registration in the VoIP communication system LAN to an associated there the second communication terminal KE2.

If booting the host computer SIPSRV but is not yet no function provided that a verification Registration - also called 'PIN code Activation' - all monitored Communication terminals in the VoIP communication system LAN makes. the subscriber logs into so while the Host due to maintenance or due to a Malfunction is out of service or not communicating in a State, enters an undefined State.

The below - turn based exchanged control messages - Described methods, the aforementioned Problem solved.

If booting the host computer SIPSRV inquiry is made a state image - in the art also 'Snapshot' called - Credential each the VoIP communication system LAN associated communication terminal via the application interface. This method Use a service for a dynamic state illustration - 'Snapshot Device Service' - in addition to the determination a credential for any other adjustments applicable to dynamic changes of state, for example, to determine call states, offered Features etc.

Similar to the embodiments made with reference to FIG. 4C is also in Fig observed. 7 that an exchange of control and signaling data not with the actual communication terminal KE1 done, but with a communication terminal KE1 managed instance in the central communication device PBX. The representation of two time lines for 1.2 the instance of the first communication terminal KE 1 in the central communication device PBX and the central Communication device PBX aims to exemplary Representation of an instance of a communication terminal which for each of the central communication device PBX managed communication terminal a - not shown - similarly configured instance exists.

At the time t0, the master computer sends SIPSRV via the application interface APIF to the entity of the communication terminal KE1 a request message 510, which includes a The beginning of a data acquisition service - 'Service Monitor' - instructs. This request message 510 is conventional in the art also designated 'startmonitor'.

At time t1, sends the instance of the communication terminal KE1 a positive confirmation message 512 to the host computer SIPSRV which a positive acknowledgment of the request message 510 reports. This confirmation message 512 is normally referred to with 'positive monitor response'.

At time t2, the host computer sends SIPSRV via the application interface APIF to the entity of the communication terminal KE1 a request message 514, which includes a Start a service for dynamic state imaging instructing. This request message 514 is conventional in the art also designated 'Snapshot Device Service'. In an information field the request message 514 are arguments to identify the service or the communication terminal KE1 and contain the type of data requested.

At time t1, sends the instance of the communication terminal KE 1 in response to the request message 514, a status message 516 to the host computer SIPSRV. In an information field the status message 516 are the previously requested contain data, for example, so information about requiring a PIN activation of the first communication terminal was KE1 performed. This status message 516 is normally referred to with 'snapshot device data'.

The master computer SIPSRV accepts the status message 516 and manipulates. At the time t4 sends the master computer a request message 518 to the Registration Server RGSRV - 'SIP Registrar' - the case of an existing PIN activation a notification of the first communication terminal KE 1 in data sets of the Registration Server RGSRV initiates. The request message 518 is conventional in the art also called 'register-mode message 518 and has the Lokalisierungsleitrechner PRSRV depending on the value of the contained 'EXPIRE' argument - see above -. Logout and login the first communication terminal KE1 to.