Abstract:
Clients in a data network can subscribe to CTI Services and in this regard must be reachable by the CSTA gateway (CCGW). If this is not the case, because for example an error occurs in the data network, then the transmission of unnecessary messages can be prevented or stopped. The clients can be connected via a server to the CCGW, where the server monitors the status of the clients and acknowledges the messages addressed to an unreachable client with error messages. The server is preferably an XMPP server and the clients are preferably XMPP clients. In order to permit transport of the CSTA messages via XMPP, info/query stanzas according to RFC 3920 can be used, since they have the advantage over message stanzas that they can be acknowledged by a remote station.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is the United States national phase of 35 USC §371 of PCT International Application No. PCT/EP2011/006531, filed on Dec. 22, 2011, and claiming priority to EP 11 007 818.5 filed on Sep. 26, 2011, and EP 10 016 049.8, filed on Dec. 23, 2010. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    Embodiments of the invention relate to methods for monitoring of a connection in an exchange system in a telecommunications network 
         [0004]    2. Background of the Related Art 
         [0005]    Data networks are primarily used for networking computers, for example, PCs with servers. Methods and arrangements in which applications installed on computers control and monitor communication systems and communication connections are generally known as CTI solutions (CTI=Computer Telephony Integration). Both communication system ports and connections between ports can be controlled and monitored in this manner. The respective connections are temporary communication channels between two or more participants of one or more communication systems. 
         [0006]    When a CTI solution is operating, data with control and status information is transmitted each time between a communication system and a CTI application (CTI application program). For this purpose, the communication systems provide special interfaces for exchanging data, the CTI interfaces. Likewise, the applications and/or PCs provide a corresponding CTI interface for this data exchange. For this, the CTI interfaces of the communication system and those of the application are connected with one another via a data line or a data network. The maximum number of CTI interfaces is limited on one communication system so often a telephony server is connected between the communication system and the applications. 
         [0007]    The publication WO 98/51092 AI “Computer Telephony Integration Gateway” shows a public communication network with several communication systems and a private communication network with several domains that each feature computers with applications for controlling and/or monitoring of the public communication network&#39;s resources. The arrangement shown features a “CTI gateway” as a conversion device, which changes the type of data sent for controlling and/or monitoring of resources from the public communication network to the private communication network, so that this data appears as the data from one single public communication network, and conversely changes the data that is sent by the private communication network with the applications to the public communication network, as though it had been sent from a private communication network with only one application. 
         [0008]    DE 000010159636 B4 describes a method for controlling and/or monitoring of resources and connections by means of exchanging data between communication systems and at least one application, wherein the data have identifiers that differentiate the resources and the connections and the identifiers of the resources are converted during the exchange in such a way that they present themselves as the identifier of one single communication system with subscriber connections for the one or every application, characterized in that each of the identifiers of the connection between resources of different communication systems comprises one local connection number (call ID) of the communication system participating in the connection and one global connection number (call ID) and in that the global connection number (call ID) is transmitted for the application through the conversion so that it is not distinguishable from a local connection number (call ID) by the application. 
       BRIEF SUMMARY OF THE INVENTION 
       [0009]    The invention concerns a method for automatic monitoring of a connection (CTI-L) in an exchange system (PBX) in a telecommunications network (TN) with a data network (DN) in which an exchange system (PBX) of the telecommunications network is connected with an IM server (XS) of the data network via a device (CCGW), which enables the IM server to provide the computer telephony integration services of the exchange system (PBX) to a communication participant on the data network. 
         [0010]    According to embodiments of the invention, a method is provided for automatic monitoring of a connection (CTI-L) in an exchange system (PBX) in a telecommunications network (TN) with a data network (DN) in which an exchange system (PBX) of the telecommunications network is connected with an IM server (XS) of the data network via a device (CCGW), which enables the IM server to provide the computer telephony integration services of the exchange system (PBX) to a communication participant on the data network. Computer telephony integration services and messages are transmitted by a request/response mechanism that provides an error message to the sender in the event of a failure. 
         [0011]    One preferred embodiment of the present invention, whose features can also be combined with features of other embodiments, provides a method for using IQ stanzas for the request/response mechanism. 
         [0012]    One preferred embodiment of the present invention, whose features can also be combined with features of other embodiments, provides a method for using “direct presence” messages for the request/response mechanism. 
         [0013]    One preferred embodiment of the present invention, whose features can also be combined with features of other embodiments, provides a method which enables the IM server to provide computer telephony integration services of the exchange system (PBX) to a communication participant on the data network, in which an IM client (XC) is allowed to subscribe to such computer telephony integration services of the exchange system (PBX). 
         [0014]    Another preferred embodiment of the present invention, whose features can also be combined with features of other embodiments, provides a method in which the device (CCGW) performs mapping between a CSTA-specific Invoke ID (CSTA-IID) on one side and a Jabber Identifier (JID) of the IM client and/or an XMPP session ID (XSID). 
         [0015]    Another preferred embodiment of the present invention, whose features can also be combined with features of other embodiments, provides a method in which the communication between the device (CCGW) and the IM server is configured as a server-server connection. 
         [0016]    Another preferred embodiment of the present invention, whose features can also be combined with features of other embodiments, provides a method in which the communication between the device (CCGW) and the IM server is executed via a server component according to XEP  0114  or another Jabber component protocol comparable to XEP  0114 . 
         [0017]    Another preferred embodiment of the present invention, whose features can also be combined with features of other embodiments, provides a method in which the so-called Invoke ID is used for assigning a request to an associated response. 
         [0018]    Another preferred embodiment of the present invention, whose features can also be combined with features of other embodiments, provides a method in which the Invoke ID used for assigning a request to an associated response is unique across all requests. 
         [0019]    Another preferred embodiment of the present invention, whose features can also be combined with features of other embodiments, provides a method in which the IQ stanzas are used for CSTA transport via XMPP, said IQ stanzas featuring a request/response mechanism that is comparable to that request/response mechanism used by CSTA. 
         [0020]    Another preferred embodiment of the present invention, whose features can also be combined with features of other embodiments, provides a method by which an IM client generates an XMPP session ID, which is different from other XMPP session IDs for the same IM client. 
         [0021]    Embodiments are described below in more detail based on preferred exemplary embodiments and with reference to the figures. 
     
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         [0022]      FIG. 1  schematically shows a first arrangement of system components for realization of an exemplary embodiment of one method according to the invention; 
           [0023]      FIG. 2  schematically shows a second arrangement of system components for realization of an exemplary embodiment of one method according to the invention; 
           [0024]      FIG. 3  schematically shows a flow diagram of a component of a sequence of one method according to the invention based on a preferred exemplary embodiment of the invention; 
           [0025]      FIG. 4  schematically shows a flow diagram of a component of a sequence of one method according to the invention based on a preferred exemplary embodiment of the invention; 
           [0026]      FIG. 5  schematically shows a flow diagram of a component of a sequence of one method according to the invention based on a preferred exemplary embodiment of the invention; 
           [0027]      FIG. 6  schematically shows a flow diagram of a component of a sequence of one method according to the invention based on a preferred exemplary embodiment of the invention; 
           [0028]      FIG. 7  schematically shows a flow diagram of a component of a sequence of one method according to the invention based on a preferred exemplary embodiment of the invention; 
           [0029]      FIG. 8  schematically shows a flow diagram of a component of a sequence of one method according to the invention based on a preferred exemplary embodiment of the invention; 
           [0030]      FIG. 9  schematically shows a flow diagram of a component of a sequence of one method according to the invention based on a preferred exemplary embodiment of the invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0031]      FIGS. 1 and 2  schematically show the embedding of the CCGW in the entire system.  FIG. 2  shows in particular an embedding of the CCGW in the entire system. 
         [0032]    As shown in  FIG. 1 , functions of a telecommunications network TN in a data network DN, consisting of telecommunications terminals T 1 , T 2 , T 3 , T 4  and an exchange system PBX and, if applicable, additional components are integrated by integrated by connecting an exchange system PBX of the telecommunications network to an IM server XS on the data network, where the clients C 1 , C 2 , C 3  and C 4  communicate via the IM server XS, via the device CCGW, which enables the IM server to provide computer telephony integration services of the exchange system PBX to a communication participant on the data network. 
         [0033]    On the one side, the connection to the feature processing FP is established via CSTA XML here by means of a so-called CSTA service provider (CSP). On the other side, the CSTA is transmitted via XMPP to the XMPP server XS. Using the CCGW, an XMPP client S 1 , S 2  can subscribe to CTI services. Communication between the CCGW and the XMPP server can be arranged as a server-server or server-client connection as well as via a server component according to XEP  0114  or another Jabber component protocol comparable to XEP  0114 . 
         [0034]    The IM server XS also creates a connection between clients S 1 , S 2  and the Internet IN in the example shown in  FIG. 2 . VI indicates a visualization of the communication on the terminal T 1 . 
         [0035]    The XMPP protocol can serve as a typical example of an instant messaging (IM) protocol. XMPP-based client/server architectures run asynchronous to the telephone in the prior art. Automatic monitoring of a CTI link within an XMPP environment is not provided according to the prior art. 
         [0036]    According to the exemplary embodiment of the invention considered, the XMPP client subscribes to CTI services via the XMPP server with an exchange system PBX. The exchange system “PBX” provides this function through a Call Control Gateway (CCGW). The CCGW provides a gateway from the PBX to the XMPP network and is the connection between the CTI of a PBX and the XMPP server. The CTI services themselves—depending on the embodiment of the invention, for example, CSTA events and CSTA requests—are exchanged then via the XMPP network as XMPP IQ messages (so-called IQ stanzas) preferably according to RFC 3920bis. 
         [0037]    The PBX and XMPP server (XS) are connected using a Call Control Gateway (CCGW). Through this call control gateway, an XMPP client can subscribe to and provide CTI services. This concerns the CSTA call control services and events described in ECMA-269 in one embodiment. 
         [0038]      FIG. 2  schematically shows the embedding of the CCGW in the entire system realized in the form of OpenScape Office MX and the associated affected components. On one side, the connection to feature processing is established via CSTA XML. On the other side, CSTA is transmitted via XMPP to the XMPP server (in the exemplary embodiment shown in  FIG. 2 : Openfire). Using the CCGW, an XMPP client S 1 , S 2  (Spark for example) can subscribe to CTI services. To enable the transport of XML-encoded CSTA via XMPP, IQ stanzas are expanded by a &lt;csta/&gt; tag. IQ stanzas are preferred for transporting CSTA, because they offer the advantage over message stanzas that they are acknowledged by the other side. 
         [0039]    Communication between the CCGW and the XMPP server can be realized in different ways depending on the embodiment of the invention:
   a) via an XMPP server-server connection, i.e. the CCGW acts as an autonomous XMPP server.   b) via an XMPP client-server connection or another Jabber component protocol comparable to XEP  0114 , i.e. the CCGW is administered as the client in the XMPP server (e.g. Openfire).   c) as a server component according to XEP  0114  or another Jabber component protocol comparable to XEP  0114 , i.e. the CCGW is a server component of the XMPP server.   
 
         [0043]      FIG. 3  shows an exemplary embodiment of the invention using a CSTA MakeCall with MakeCall Response and an event including an acknowledgment. Client C sends the message  11  with the text  11  to the server S. The server S answers by sending the message  12  with the text  12  to the client C. The server S then sends message  13  with text  13  to the client C, whereupon the client C sends message  14  with text  14  to the server S. 
         [0044]    The texts of the messages are compiled in an overview at the end of the description. By transmitting CTI services and messages as IQ stanzas between the CCGW and the XMPP client (via XMPP server), an automatic monitoring of the CTI link from the XMPP client to its XMPP server is also ensured. Namely, if this connection is no longer present (e.g. due to a faulty LAN segment), the XMPP server must respond in place of the addressed XMPP client to an IQ stanza request with an “error” type IQ stanza with the value “service unavailable” (RFC 3920bis). In the event of error, appropriate measures for clearing the error can thereby be initiated at the CCGW on the CTI level. 
         [0045]      FIG. 4  shows an exemplary embodiment of the invention using an IQ stanza error. The device CCGW sends a message  21  with the text  21  to the server XS, whereupon the server XS sends the message  22  with the text  22  to the device CCGW. The texts of the messages are compiled in an overview at the end of the description. 
         [0046]    In the event of an unexpected disconnection, the arriving messages are not saved in the CCGW and are transmitted by the CCGW during the next login of the corresponding user. That is to say if this user has set a monitoring point on a device, then the unidirectional CSTA events are forwarded to the user. These events are only relevant for a limited period however. If the user logs into the XMPP server hours or even days after the last disconnection, then it is completely irrelevant which events occurred in the user&#39;s absence. Rather, the sender of the CSTA events (i.e. the CCGW) can cancel the monitoring point by receiving the error type IQ stanza and therefore stop sending additional, unnecessary XMPP messages. Another option for starting and/or stopping transmission of CTI services and messages using IQ stanzas between CCGW and XMPP clients (via XMPP server) is the use of “directed presence” messages (RFC 3921bis). In this case, the XMPP client sends its presence status (for example in the form: unavailable) directly to the CCGW. The CCGW recognizes the online status of the XMPP client and can respond accordingly. The use of the directed presence mechanism furthermore has the added advantage that the CCGW does not have to be located in the roster (contact list) of the user to get presence messages, and thus the user always sees only his contact list with “real” users. 
         [0047]    The behavior of an XMPP server in response to the receipt of different message types is defined for different cases within the RFC 3921bis. The described cases, for example, include that the Jabber ID does not exist, or that the JID exists, but is not available via the addressed resource. The configurations of this RFC administer XMPP servers upon receipt of an IQ message, that either is not addressed directly to a resource or if the addressed resource is not available, in that the server responds with the &lt;service unavailable/&gt; error type. In this case, an error on the IQ stanza request of the CSTA event type could automatically stop or pause the CSTA monitoring point. 
         [0048]    So-called XMPP direct presence messages (RFC 3921bis) can also be used in order to inform the device CCGW about the online status of its clients, even if the CCGW is not found in the user roster. To achieve this, the client would have to address a presence message directly to the CCGW If the XMPP client server switches off the XMPP client server in a controlled fashion (i.e. the user closes the XMPP client application), the client application sends an “unavailable” type of presence stanza to its XMPP server. According to RFC 3921bis, this presence stanza must also be sent by the XMPP server to the XMPP terminals that were previously provided by the client application with direct presence messages (i.e. also to the CCGW). The CCGW can then stop the CSTA monitoring point in the CCGW. Because the XMPP server monitors the XMPP connection to its XMPP clients, the XMPP server also notices whether the connection to an XMPP client was lost in an uncontrolled manner (e.g. by failure of the corresponding LAN segment). This XMPP client is now no longer reachable, so it receives the status “unavailable”. The XMPP server must also independently inform any XMPP entities that previously only received “directed presence” stanzas from this client with an “unavailable” type presence stanza (thus, also the CCGW) (see RFC 3921 bis). 
         [0049]    In both cases (i.e. in controlled and uncontrolled interruptions of the XMPP client-server connection), the “directed presence” functionality according to RFC 3921bis can therefore automatically be used to stop or pause the CSTA monitoring point in the CCGW. 
         [0050]    The cited documents can be retrieved on the Internet at the website of the International Engineering Task Force. It is assumed here that 3920bis19 and 3921bis17 replace the existing RFC 3920 and RFC 3921. 
         [0051]      FIGS. 5 to 9  show further exemplary embodiments of the invention in which the connection between the CCGW and XMPP server is realized as a client-server connection. The CCGW device in these cases is preferably likewise administered as an XMPP client on the XMPP server.  FIG. 5  shows the transmission of CSTA services and events. The client C is preferably an XMPP client, the server S is an XMPP server that takes on a purely passive role as a router. The client C sends a message  31  with the text  31  to the server XS, whereupon the server XS sends a message  32  with the text  32  to the device CCGW. The device CCGW now sends a message  33  with the text  33  to the server XS, whereupon the server sends a message  34  with the text  34  to the client. Afterwards, the device CCGW sends a message  35  with the text  35  to the server, whereupon the server sends a message  36  with the text  36  to the client C. Afterwards, the client C sends a message  37  with the text  37  to the server, whereupon the server sends a message  38  with the text  38  to the device CCGW. 
         [0052]      FIG. 6  shows the behavior when the client is not available. The device CCGW sends a message  41  with the text  41  to the server XS, whereupon the server XS sends a message  43  with the text  43  to the device CCGW. Sending of a message  42  by the server to the client C does not happen here. The XMPP server takes on an active role here because no “end-to-end” connection exists (any longer). 
         [0053]      FIG. 7  shows a further exemplary embodiment of the invention based on the use of direct presence messages. Here, the XMPP client has the address test@example.com/test, the server S is an XMPP server, and the device CCGW is set up as an XMPP client with the address ccgw@example.com/ccgw. The client C sends a message  51  with the text  51  and subsequently a message  52  with the text  52  to the server. Thereupon the server sends a message  53  with the text  53  to the device CCGW. The client C sends a message  54  with the text  54  and subsequently a message  55  with the text  55  to the server. Thereupon the server sends a message  56  with the text  56  to the device CCGW. Afterwards, the client C sends a message  57  with the text  57  to the server. In this example, the XMPP client sends the direct presence status to the device CCGW for logon and logoff. 
         [0054]    In the exemplary embodiment shown in  FIG. 8 , the XMPP client C has the address test@example.com/test, the server S is an XMPP server, and the device CCGW is set up as an XMPP client with the address ccgwgexample.com/ccgw. Upon a logoff without direct presence status by the client, the server assumes this task. The client C sends a message  61  with the text  61  and a message  62  with the text  62  to the server, whereupon the server sends a message  63  with the text  63  to the device CCGW. The client C then sends a message  64  with the text  64  and a message  65  with the text  65  to the server, whereupon the server sends a message  63  with the text  66  to the device CCGW. 
         [0055]    In the exemplary embodiment in  FIG. 9 , the XMPP client C has the address test@example.com/test, the server S is an XMPP server, and the device CCGW is set up as an XMPP client with the address ccgw@example.com/ccgw. For connection interruptions between the client and server, the server must send the direct presence status. The client C sends a message  71  with the text  71  and a message  72  with the text  72  to the server, whereupon the server sends a message  73  with the text  73  to the device CCGW. The client C then sends a message  74  with the text  74  to the server, whereupon the server sends a message  76  with the text  76  to the device CCGW. Sending of the message  75  by the client C to the server S does not happen in this case. 
         [0056]    Below is a list of the message texts used in the description that is an express component of the present description. 
         [0000]    
       
         
               
             
           
               
                   
               
             
             
               
                 Text 11: 
               
               
                 &lt;iq from=“test@example .com/test ” to=“ccgw@example. com/ccgw” 
               
               
                 xml :lang=“en” 
               
               
                 id=“123456” type=“set”&gt; 
               
               
                 &lt;csta xmlns=“csta” version=“ 1 .0” encoding=“UTF-8 ”&gt; 
               
               
                 &lt;MakeCall xmlns=“http ://www.ecma- ... 
               
               
                 Text 12: 
               
               
                 &lt;iq from=“ccgw@example. com/ccgw” to=“ test@example. com/test ” 
               
               
                 xm1 :lang=“en” 
               
               
                 id=“123456” type=“result ”&gt; 
               
               
                 &lt;csta xmlns=“csta” version=“1 .0” encoding=“UTF-8 ”&gt; &lt;MakeCallResponse 
               
               
                 xmlns=“http: //www.ecma-... 
               
               
                 Text 13: 
               
               
                 &lt;iq from=“ccgw@example .com/ccgw” to=“test@example .com/test ” xml :lang=“en” 
               
               
                 id=“234567” type=“set”&gt; 
               
               
                 &lt;csta xmlns=“csta” version=“1 .0” encoding=“UTF-8 ”&gt; 
               
               
                 &lt;ServiceInitiatedEvent xmlns=“http ://www.ecma- 
               
               
                 Text 14: 
               
               
                 &lt;iq from=“test@example. com/test ” to=“ccgw@example. com/ccgw” 
               
               
                 xml :lang=“en” 
               
               
                 id=“234567” type=“result ” /&gt; 
               
               
                 Text 21: 
               
               
                 &lt;iq to=“seb@wit0234c/sebl” type=“set” 
               
               
                 from=“ccgw@wit0234c/ccgw” 
               
               
                 xmlns=“jabber: client” id=“as234sf d”&gt; 
               
               
                 &lt;csta xmlns=“csta” version=“1 .0” encoding=“UTF-8 ”&gt; &lt;EstablishedEvent xmlns 
               
               
                 :csta=“http ://www. ecma- ... 
               
               
                 ... 
               
               
                 &lt;/EstablishedEvent&gt; 
               
               
                 &lt;/esta&gt; 
               
               
                 &lt;/iq&gt; 
               
               
                 Text 22: 
               
               
                 &lt;iq from=“seb@wit0234c/sebl” to=“ccgw@wit0234c/ccgw” 
               
               
                 type=“error” 
               
               
                 id=“as234sfd”&gt; 
               
               
                 &lt;csta xmlns=“csta” version=“1 .0” encoding=“UTF-8”&gt; 
               
               
                 &lt;EstablishedEvent xmlns :csta=“http ://www. ecma- ... 
               
               
                 ... 
               
               
                 &lt;/csta&gt; 
               
               
                 &lt;error code=“503” type=“cancel ”&gt; 
               
               
                 &lt;service-unavailable 
               
               
                 xmlns=“urn :iet f :params :xml :ns :xmppstanzas” /&gt; 
               
               
                 &lt;/error&gt; 
               
               
                 &lt;/iq&gt; 
               
               
                 Text 31: 
               
               
                 &lt;iq from=“test@example . com/test” to=“ccgw@example . 
               
               
                 com/ccgw” 
               
               
                 id=“123456” type-“set” &gt; 
               
               
                 &lt;csta xmlns=“csta” version=“1 .o” encoding=“UTF- 8” &gt; 
               
               
                 &lt;MakeCall xmlns=“http ://www . ecma- ... 
               
               
                 Text 32: 
               
               
                 &lt;iq from=“test@example .com/test” to=“ccgw@example .com/ccgw” 
               
               
                 id=“123456” type=“set” &gt; 
               
               
                 &lt;csta xmlns-“csta” version-“I .0” encoding-“UTF- 8” &gt; 
               
               
                 &lt;MakeCall xmlns-“http ://www .ecma- ... 
               
               
                 Text 33: 
               
               
                 &lt;iq from=“ccgw@example .com/ccgw” to=“test@example .com/test” 
               
               
                 id=“123456” type=“result ” &gt; 
               
               
                 &lt;csta xmlns=“csta” version=“1 .o” encoding=“UTF- 8” &gt; 
               
               
                 &lt;MakeCallResponse xmlns- “http ://www .ecma- ... 
               
               
                 Text 34: 
               
               
                 &lt;iq from=“ccgw@example .com/ccgw” to=“test@example .com/test ” 
               
               
                 id=“123456” type=“result ” &gt; 
               
               
                 &lt;csta xmlns=“csta” version=“1 .0” encoding=“UTF- 8” &gt; 
               
               
                 &lt;MakeCallResponse xmlns- “http ://www. ecma- ... 
               
               
                 Text 35: 
               
               
                 &lt;iq from=“ccgw@example .com/ccgw” to=“test@example .com/test” 
               
               
                 id-“234567” type-“set” &gt; 
               
               
                 &lt;csta xmlns=“csta” version=“1 .0” encoding=“UTF 8” &gt; OervicelnitiatedEvent 
               
               
                     xmlns=“ http : //www . ecma- ... 
               
               
                 Text 36: 
               
               
                 &lt;iq from=“ccgw@example .com/ccgw” to=“test@example .com/test ” 
               
               
                 id=“234567” type=“set” &gt; 
               
               
                 &lt;csta xmlns=“csta” version=“ 1 .0” encoding= “UTF- 8” &gt; &lt;ServiceInitiatedEvent 
               
               
                 xmlns=“ http : //www . ecma- ... 
               
               
                 Text 37: 
               
               
                 &lt;iq from-“test@example .com/test” to-“ccgw@example . 
               
               
                 com/ccgw” 
               
               
                 id=“234567” type=“result ” / &gt; 
               
               
                 Text 38: 
               
               
                 &lt;iq from-“test@example .com/test” to-“ccgw@example .com/ccgw” 
               
               
                 id=“234567” type=“result ” / &gt; 
               
               
                 Text 41 = Text 35 
               
               
                 Text 43: 
               
               
                 &lt;iq from= “test@example .com/test” to= “ccgw@example . 
               
               
                 com/ccgw” 
               
               
                 id= “234567” type= “error” &gt; 
               
               
                 &lt;csta xmlns= “csta” version=“1 .0” encoding=“UTF- 8” &gt; &lt;ServiceInitiatedEvent 
               
               
                 xmlns= “http://www.ecma- .. 
               
               
                 &lt;/csta&gt; 
               
               
                 &lt;error code= “503” type= “cancel” &gt; 
               
               
                 &lt;service- unavailable xmlns= “urn : ietf : params : xml :. 
               
               
                 .. ”/&gt; 
               
               
                 &lt;/error&gt; 
               
               
                 &lt;/iq&gt; 
               
               
                 Text 51: 
               
               
                 &lt;presence/&gt; 
               
               
                 Text 52: 
               
               
                 &lt;presence to= “ccgw@example .com/ccgw” /&gt; 
               
               
                 Text 53: 
               
               
                 &lt;presence from= “test@example .com/test” 
               
               
                 to= “ccgw@example .com/ccgw” /&gt; 
               
               
                 Text 54: 
               
               
                 &lt;presence&gt; 
               
               
                 &lt;show&gt;away&lt;/ show&gt; 
               
               
                 &lt;status&gt;gone fishing&lt;/status&gt; 
               
               
                 &lt;/presence&gt; 
               
               
                 Text 55: 
               
               
                 &lt;presence to= “ccgwgexample .com/ccgw” type= “unavailable” 
               
               
                 /&gt; 
               
               
                 Text 56: 
               
               
                 &lt;presence from= “test@example .com/test” 
               
               
                 to= “ccgw@example .com/ccgw” type= “unavailable” / &gt; 
               
               
                 Text 57: 
               
               
                 &lt;presence type= “unavailable” / &gt; 
               
               
                 Text 61 = Text 51 = Text 71 
               
               
                 Text 62 = Text 52 = Text 72 
               
               
                 Text 63 = text 53 = Text 73 
               
               
                 Text 64 = Text 54 = Text 74 
               
               
                 Text 65 = Text 57 
               
               
                 Text 66 = Text 56 = Text 76 
               
               
                   
               
             
          
         
       
     
         [0057]    The invention is not limited to the exemplary embodiments as described; the person skilled in the art can discover further exemplary embodiments of the invention based on the description given here.