Abstract:
A method of communication between communications networks in which different communication protocols are used and which are connected to each other by way of at least one intermediate node. In order to communicate easily between the networks, both the destination node and the start node are prompted to use a common communication protocol by the intermediate node in that this node transmits messages to the destination node and the start node upon reading destination node information from a data collection.

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to a method of communication between communications networks which use different communication protocols and which are connected to each other by way of at least one intermediate node. 
   2. Description of the Prior Art 
   Communication methods such as this are presently being applied, particularly in the current climate of liberalization of the telecommunication markets. In this regard, network operators are being required to open their networks to other operators. The networks of the different operators are then connected to one another by way of common network nodes, which are herein referred to as intermediate network nodes. 
   One imaginable way to enable communication between these networks is for the intermediate network node to convert all messages it receives into the communication protocol of the network serving as the communication destination. But this solution requires a substantial outlay in the intermediate node as well as a high computing power, given that all messages must be completely decoded and then recoded in the new communication protocol. 
   An object of the present invention, therefore, is to lay out a method with which it is possible to easily communicate between networks in which different communication protocols are used. 
   SUMMARY OF THE INVENTION 
   Accordingly, the present invention is directed to a method wherein: at the start of a communication with a destination node of a second network, a start node of a first network sends a start message that is set up using a first communication protocol, which is used in the first network, to the intermediate node; next, with the aid of destination node information that is read from a data collection, the intermediate node prompts both the destination node and the start node, by sending messages to the destination node and the start node, to use a common communication protocol that is used in both the first and second networks for communication between the start node and the destination node; and subsequent messages between the start node and the destination node which are set up according to the common communication protocol are forwarded by the intermediate node without modification. 
   WO 00/22789 discloses a method in which communication links are established between incompatible networks via a controller node in that the controller node informs adapters assigned to the incompatible networks about the use of a predetermined communication protocol or performs the translation of the various communication protocols itself. However, this method merely serves to make communication between the networks possible at all. 
   The advantage of the method of the present invention is that the intermediate node is required to act only at the start of the communication for purposes of prompting the destination node and the start node to use a common communication protocol. Subsequent messages between the start node and the destination node are then no longer modified by the intermediate node but are simply relayed without modification (“transparent routing”). 
   One embodiment of the method according to the present invention provides that, when prompted, messages sent by the destination node to the starting node are checked once by the intermediate node for the presence of a common communication protocol, and subsequent messages between the starting node and the destination node are forwarded without being checked if it is determined that the common communication protocol is present. Such method is particularly advantageous in that only a single check of the messages need be carried out. 
   A particular embodiment of the inventive method provides that the start node and the destination node be prompted to use the common communication protocol by the readout of an identifier of the common communication protocol by the intermediate node as the destination node information; the modification of the start message by the intermediate node by replacement of a protocol identifier of the first communication protocol, which is contained in this message, with the identifier presently read out; the transmission of the modified start message to the destination node by the intermediate node; the transmission of a start reply message to the intermediate node by the destination node according to the common protocol; and the transmission of the start reply message to the start node by the intermediate node. This method requires a very small outlay by the intermediate node, given that the intermediate node merely modifies the protocol identifier in the start message. The method presumes that the destination node is able “to understand” (i.e., decode) the start message that was set up according to the first communication protocol and then to generate a start reply message. 
   Another embodiment of the inventive method provides that the start node and the destination node be prompted to use the common communication protocol by the following sequence of events: an identifier of at least one communication protocol which is a suitable common protocol is read out by the intermediate node as the destination node information; with the aid of the destination node information, the intermediate node checks whether the first communication protocol is such a suitable common communication protocol; if the protocol is not a suitable common protocol, a notification message is sent to the start node, which sends another start message, which is set up according to a second communication protocol, to the intermediate node; and the process of checking, sending the notification message, and sending another start message is repeated until the start node sends a start message in a suitable common protocol; whereupon the start message is sent by the intermediate node to the destination node; a start reply message that is set up according to the suitable common communication protocol is sent by the destination node to the intermediate node; and the start reply message is sent by the intermediate node to the start node. The advantage of this method is that the destination node always “understands” the start message, because the start message is set up according to the common communication protocol. 
   Another embodiment of the inventive method provides that the start node and the destination node be prompted to use the common communication protocol by the following sequence of events: at least one identifier of at least one protocol that is suitable as a common communication protocol is read out by the intermediate node as the destination node information; with the aid of the destination node information, the intermediate node checks whether the first communication protocol is a suitable common communication protocol; if the first protocol is not suitable, a notification message which contains an identifier of a suitable common communication protocol is sent to the start node; whereupon an additional start message, which is set up according to this common communication protocol, is sent by the start node to the intermediate node; the start message is sent by the intermediate node to the destination node; a start reply message which is set up in this common communication protocol is then sent by the destination node to the intermediate node; and the start reply message is sent by the intermediate node to the start node. This embodiment is particularly advantageous in view of the immediate communicating of an identifier of a suitable common protocol to the start node in the notification message, for which reason the method of this embodiment is particularly fast. 
   The inventive method can be advantageously set up such that the start reply message is sent from the intermediate node to the start node only when a check of the start reply message by the intermediate node reveals that it was set up according to the common communication protocol. This guarantees that the start reply message is sent to the start node only when it has truly been set up by the destination node according to the common communication protocol. This method thus provides a particularly effective guarantee against the utilization of an unsuitable communication protocol; i.e., a protocol that cannot be used in common. 
   A further embodiment of the inventive method provides that the start node and the destination node be prompted to use the common communication protocol by the following sequence of events: the start message is forwarded to the destination node by the intermediate node without modification; the destination node checks, with the aid of information read from a data memory accessible to it, whether the first communication protocol is a common protocol; if the check produces a positive result, a start reply message according to the first communication protocol is sent to the intermediate node; or if the check result is negative, an identifier of a communication protocol for communication with the start node is read from the data memory; a start reply message that is set up according to this protocol is sent by the destination node to the intermediate node; the intermediate node checks whether the communication protocol of the start reply message is a common communication protocol; and if so, the start reply message is sent to the start node by the intermediate node. This method is particularly easy to carry out from the standpoint of the intermediate node, because this forwards the start message to the destination node without modification and merely checks whether the subsequently received start reply message is set up according to a common communication protocol. 
   Another advantageous embodiment of the inventive method provides for the initiation of a communication between the start node and the destination node in order to make it possible for services to be provided by the destination node to a user which is connected to the start node. This way, services can be provided between nodes (in the present example, by the destination node for the start node) even when these nodes are located in different communications networks in which different communication protocols are used. 
   Another embodiment of the inventive method is characterized in that a service switching point of an intelligent network is used as the start node. 
   In a further embodiment of the method, it is provided that a service control point of an intelligent network be used as the destination node. This way, the inventive method can be used in communications networks having the structure of an intelligent network. Service switching points (SSP) and service control points (SCP) are typical components of such intelligent networks. 
   Yet another embodiment of the inventive method provides that the start node and the destination node be prompted to use an INAP protocol version as the common communication protocol. The INAP protocol (Intelligent Network Application Protocol) is typically used in intelligent networks based on signaling system no. 7 and is described in  Intelligent Network  ( IN );  Intelligent Network Capability Set  1 ( CS 1),  Core Intelligent Network Application Protocol  ( INAP );  Part  1:  Protocol Specification  (ETS 300 374-1; European Telecommunications Standards Institute). The INAP protocol uses the TCAP standard (Transaction Capabilities Application Part). The TCAP standard prevents the start node and the destination node from switching from the common communication protocol to another protocol in the course of a running communication after they have been prompted to use this common protocol. 
   Additional features and advantages of the present invention are described in, and will be apparent from, the following Detailed Description of the Preferred Embodiments and the Drawings. 

   
     DESCRIPTION OF THE DRAWINGS 
       FIG. 1  shows a schematic of an exemplifying embodiment of two communications networks that are connected by way of an intermediate node; 
       FIG. 2  shows a schematic of the sequence of an exemplifying embodiment of the inventive method; 
       FIG. 3  shows another schematic of the sequence of an exemplifying embodiment of the inventive method; 
       FIG. 4  shows another schematic of the sequence of an exemplifying embodiment of the inventive method; 
       FIG. 5  shows another schematic of the sequence of an exemplifying embodiment of the inventive method; and 
       FIG. 6  shows a schematic of a separate exemplifying embodiment of two connected communications networks. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   On the left side of  FIG. 1 , a communications network  1  is represented which includes network nodes, which are represented as points, and connections between these nodes, which are represented as lines. These nodes can be local exchanges, service switching points, or service control points. One of these nodes is a start node  4 , which is defined in this context as a node from which a communication connection is set up. The communications network  1  is connected by way of an intermediate node  8  to another communications network  10 , which likewise includes nodes and connections between them. Another node of this additional communications network is a destination node  11 , to which a communication connection will be set up originating at the start node. The start node  4  of the communications network  1  is connected to the destination node  11  of the second communications network  10  by way of the intermediate node  8 . 
   It is noted that the connection between the start node  4  and the intermediate node  8  need not necessarily be a direct connection; rather, additional nodes may be included between the start node  4  and the intermediate node  8 , which relay the messages between the start node and the intermediate node  8  without modifying those contents which are relevant to the described method. The same applies to the connection between the intermediate node  8  and the destination node  11 , accordingly. 
     FIG. 2  shows how messages are exchanged between the start node  4 , the intermediate node  8  and the destination node  11 . The messages are represented as arrows. The capital letters in the arrows (A and C in this case) reference the communication protocol in which the corresponding messages are set up. The time sequence of the transmission of messages runs from top to bottom. The message flow begins on the upper left-hand side at start node  4 . 
   First, the start node  4  included in the network  1  sends a start message  20  that is set up according to the first communication protocol A, which is used in the first communications network, to the intermediate node  8 . From the contents of the message  20 , the intermediate node  8  recognizes that this message is intended to be sent to the destination node  11  of the other communications network. The intermediate node  8  reads from a database  21 , which is contained in the intermediate node  8  or connected thereto, that the communication between the start node  4  and the destination node  11  should occur via a communication protocol C. It reads an identifier of the communication protocol C, which is intended as the common protocol of communication between the start node  4  and the destination node  11 , from the database  21 . 
   The intermediate node  8  then modifies the start message  20  by replacing an identifier of protocol A that is contained in this start message with the identifier, which it read from the database  21 , of protocol C. The start message remains in protocol A, however. The modified start message  23  is then forwarded to the destination node  11 . The destination node  11  recognizes from the identifier C of the modified start message  23  that a communication is requested via messages that are set up according to protocol C and sends a start reply message  25  back to the intermediate node according to the common protocol C. 
   The intermediate node  8  now has the option to check whether the start reply message  25  was actually set up according to protocol C, which checking process is symbolized in the Figure by the letter “P” in the first node  8 . This optional check increases the security of the method particularly when it must be guaranteed that the destination node  11  actually replies with a start reply message that is set up according to the protocol whose identifier was sent to the destination node with the modified start message  23 . In case the result of the check is negative, an error processing operation is triggered; for instance, the communication can be interrupted, and the malfunctioning of the destination node vis a vis the intermediate node can be logged in an error list. 
   If the check result is positive, the start reply message  25  is relayed to the start node  4  unchanged. The start node  4  then derives from the start reply message  25  that was set up according to protocol C that the communication with the destination node  11  is to be conducted via messages that are set up according to protocol C. At this moment, both the destination node  11  and the start node  4  have been prompted by the intermediate node  8  to use the common protocol C for communication. Accordingly, a subsequent message  27  is set up by the start node  4  according to protocol C and sent to the intermediate node. The intermediate node  8  sends this message  27  to the destination node without modification. The destination node  11  then sets up the next message  28  to be sent to the start node  4  according to protocol C as well, and sends it back to the intermediate node. The intermediate node routes the message  28  to the start node  4  unchanged. All subsequent message transmissions to occur during this communication are thus set up according to the common protocol C and forwarded to the respective destination by the intermediate node  8  without modification. 
     FIG. 3  shows how, at the start of a communication with the destination node  11  of the second communications network, a start message  40  that is set up according to communication protocol A, the protocol used in the first communications network, is sent by the start node  4  of the first communications network to the intermediate node  8 . Next, the intermediate node  8  reads destination information about the destination node  11  from a database  41  indicating which communication protocols can be used as the common communication protocol for communication between the start node  4  and the destination node  11 . Based on this destination node information, the intermediate node  8  determines that the first communication protocol A is unsuitable as the common communication protocol. It therefore sends a notification message  43  to the start node  4  informing this node that the communication protocol A is not a common communication protocol for the start node and the destination node. On its part, the start node  4  has a table of possible communication protocols. It pulls a second protocol B from this table, sets up an additional start message  44  using this second communication protocol B, and sends this to the intermediate node  8 . The intermediate node  8  again determines that the second communication protocol B is not suitable as a common communication protocol and thus sends back another notification message  46  to the start node  4 . With this additional notification message  46 , the start node is informed that the communication protocol B is not a common communication protocol. The start node  4  then draws another communication protocol from its table, protocol C; sets up another start message  48  using this protocol; and sends this message to the intermediate node  8 . Now, the intermediate node  8  determines that the third communication protocol C is suitable as a common communication protocol, whereupon it forwards the start message  48  to the destination node  11 . From the start message  48 , the destination node recognizes that further communication steps must be handled according to this communication protocol C, and it sets up a start reply message  50  using this protocol C and sends it back to the intermediate node  8 . The intermediate node now has the option of checking whether the start reply message  50  was set up according to the same communication protocol as the start message  48  (in this case communication protocol C). If not, an exception handling operation can be initiated, as is described in connection with  FIG. 2 . If the check produces a positive result, the start reply message  50  is forwarded to the start node. The start node  4  then recognizes from the start reply message  50  that further communication must be handled using the communication protocol C; accordingly, subsequent messages  52  and  54  are set up according to protocol C and delivered to their respective destinations by the intermediate node without modification. 
   The method described in  FIG. 4  initially runs identically to the method described in  FIG. 3 . As described in connection with  FIG. 3 , a start message  60  that is set up according to a first communication protocol A is sent to the intermediate node  8 . Based on destination node information that is read from a database  61 , the intermediate node  8  determines that the first communication protocol A is not suitable as a common communication protocol and that a communication protocol C can be used as the common communication protocol. The intermediate node then sends a notification message  63  back to the start node  4 . This notification message  63  contains the information that the communication protocol A is not suitable as the common communication protocol and that the communication protocol C must be used as the common communication protocol instead. The start node  4  then sets up a second start message  65  according to the common communication protocol C and sends it to the intermediate node  8 , which relays this start message  65  to the destination node  11 . From the start message  65 , the destination node  11  recognizes that the communication must proceed via messages that are set up according to the common communication protocol C, and it sends a start reply message  67  that is set up according to this protocol C back to the intermediate node. The remainder of the sequence, which includes the optional checking of the start reply message  67  in the intermediate node, the forwarding of this message to the start node  4 , and the transmission of subsequent messages  70  and  71  which are set up according to the common communication protocol C to the start node and the destination node, respectively, corresponds to the method described in connection with  FIG. 3 . 
     FIG. 5  shows another embodiment of the method of the present invention. Again, at the start of the process a start message  80  that is set up according to the first communication protocol A is sent by the start node  4  to the intermediate node  8 . Unlike in the previous methods, the intermediate node forwards this start message  80  to the destination node  11  unchanged. The destination node  11  now checks, with the aid of information stored in a data memory  82  that is accessible to it, whether the first communication protocol A is suitable as a common communication protocol for communication with the start node  4 . If not, the destination node reads an identifier of a protocol C, which is a suitable common communication protocol, from the data memory  82  and sets up a start message  84  using this communication protocol C. It then sends this start message  84  to the intermediate node  8 . The intermediate node  8  reads destination node information from an accessible database  85 , which indicates whether the communication protocol C is a suitable communication protocol. If not, the communication proceeds with an error processing operation such as was described in connection with  FIG. 2 . If the result of the check is positive, the intermediate node  8  relays the start reply message  84  to the start node  4  unchanged. The start node  4  recognizes from the start reply message  84  that further communication is to proceed according to the common communication protocol C and sets up another message  86  according to this communication protocol C. This other message  86  and all subsequent messages (e.g., the message  87 ) of this communication are now relayed by the intermediate node to the destination node or the start node without modification, in known fashion, and the intermediate node no longer intervenes in the communication between the start node and the destination node. 
     FIG. 6  shows a possible situation in which the inventive method may run. A network node of a communications network  101  is formed by a communication terminal device KE (e.g., a telephone); a second node is formed by a local exchange LX; and the start node cited in  FIG. 1  is formed by a service switching point SSP. The destination node of another network  110  as cited in  FIG. 1  is formed by a service control point SCP. The communications network  101  is connected to the other network  110  by an intermediate node  108 . 
   A service which can be called up in a telephone communications network  101  (e.g., request for information) is called up by the communication terminal equipment KE which represents a service user. What is known as a service number is then dialed via the communication terminal device KE, and a connection is set up to the service switching point SSP by way of the local exchange LX. With the aid of the service number, the service switching point SSP recognizes that the service is provided by the service control point SCP. The service control point SCP is located in the other communications network  110 . 
   The service switching point SSP is part of a structure of an intelligent network; both the communications network  101  and the other communications network  110  are structured as intelligent networks. The communications network  101  uses a first version of the INAP communication protocol, called INAP 1 . This protocol INAP 1  has a very broad range of functions and allows diverse mutual influences of the elements of the structure of the intelligent network in the communications network  101 . But when these elements communicate with elements of the intelligent network structure of the other communications network  110 , it is undesirable to conduct this communication according to the INAP 1  protocol for reasons of security, because the elements of the other communications network  110  also would have the diverse capability to influence the communications network  101 . Therefore, this communication should be conducted according to a second version of the INAP protocol, called INAP 2 , which is limited compared to the first version INAP 1 . 
   In other words, a communication between the service switching point SSP and a service control point which is also located in the communications network  101  (but is not represented in  FIG. 101 ) would proceed according to the INAP 1  protocol. But a communication between the service switching point SSP and the service control point SCP which is located in the other communications network  110  should be handled according to the INAP 2  protocol. The distinction made between the protocols INAP 1  and INAP 2  also represents the distinction between what are known as application contexts (AC). For communication between the service switching point SSP and the service control point SCP, the methods which are closely described in connection with the  FIGS. 2 to 5  are used. 
   Although the present invention has been described with reference to specific embodiments, those of skill in the art will recognize that changes may be made thereto without departing from the spirit and scope of the invention as set forth in the hereafter appended claims.