Patent Publication Number: US-2004044782-A1

Title: Transmission of service control information via at least one intermediate station

Description:
[0001] The present invention relates to a method as well as to a system for transmission of services control data by way of at least one signaling segment containing at least one intermediate station.  
       [0002] In the state of the art (see FIG. 4), it is possible to communicate with another data terminal  8  (H.323 terminal), by way of the Internet, using an analog telephone  1  or an ISDN telephone  2 . For this purpose, an exchange-side switching center  3  (e.g., EWSD) of the public telephone network  4  is connected with a local network  7  (Ethernet) by way of an H.323 gateway  5 .  
       [0003] In this connection, H.323 is an international standard for voice, data, and video communication by way of packet-oriented networks. It establishes the specific capabilities of terminals in the IP (Internet protocol) environment.  
       [0004] A gateway  5  is understood to mean the hardware and software that is required in order to connect different networks (here, the public telephone network  4  and the Ethernet  7 , i.e., the connection-oriented ISDN network and the packet-oriented Ethernet, for example) with one another. A gateway  5  has the task of transmitting messages from one computer network into another computer network, for which purpose it is primarily necessary to translate the communications protocols. It can be viewed as a type of protocol converter that understands the protocols on both sides and represents an addressable network node in both networks.  
       [0005] The local network  7  (Ethernet) is connected with the H.323 terminal by means of a router  10 , by way of the Internet  9 . Routers  10  connect sub-networks on the switching layer of the OSI reference model.  
       [0006] The central control element for routing the call signaling, but also for resolving the telephone numbers as well as the IP address, i.e., converting them, is the H.323 subscriber switching center  6  (gatekeeper) that is also connected to the local network  7  (Ethernet). The gatekeeper  6  is responsible for access entitlement and security. Furthermore, the gatekeeper  6  records the charges and assigns them to the partners in the networks.  
       [0007] In every case, the above arrangement (FIG. 1) makes it possible to telephone by means of an H.323 terminal  8 , in other words by means of an ISDN data terminal for data input and data output, which generally consists of a keyboard, a screen, and a processor, by way of the local network  7  as well as by way of the Internet  9 .  
       [0008] However, when different networks are linked by such a gateway, there is the great disadvantage that in connection with use for telephony by way of the Internet, a number of additional services familiar from ISDN technology (Supplementary Services), such as call forwarding, display of charges, call waiting, etc., are not possible.  
       [0009] This is because the DSS1 protocol developed for control of ISDN terminals only has local significance, i.e., it is only designed for communication between two adjacent stations. According to the state of the art, the switching center (e.g., EWSD)  3  in the public telephone network  4 , as the first end point, therefore cannot transmit control data for supplementary services to a data terminal  8  as the second end point, by way of the gateway  5  as an intermediate station.  
       [0010] One possibility for circumventing this problem is to use a protocol QSIG derived from the DSS1 protocol, which can span several stations by means of the introduction of a special data element (the so-called NFE “Network Facility Extension”). However, this is connected with a change in the exchange-side switching center and therefore with a significant expenditure of costs.  
       [0011] It is therefore the task of the present invention to inexpensively make all supplementary services available, as they correspond to a normal telephone connection, also when telephoning over the Internet, using an appropriate data terminal (e.g., PC).  
       [0012] This task is accomplished, according to the present invention, in that the intermediate station (e.g., gateway) has a services distributor that serves as a unit for differentiating services control data to be carried out locally and services control data to be passed farther along the signaling segment.  
       [0013] In the differentiation, the services distributor makes use of a code, by means of which each service is assigned to a specific station.  
       [0014] After the services control data have been processed, a confirmation can be sent to the source of the services request (as a function of the service, in each instance), which confirmation contains information that guarantees that the confirmation is distributed to the correct location.  
       [0015] The intermediate station has a protocol entity to which the services distributor is coupled, and which transfers all the received services control data and any additional further information on to the services distributor.  
       [0016] Furthermore, according to the invention, a method for transmitting services data from a first end point by way of at least one intermediate station, spanning a signaling segment to a second end point, is claimed, this method comprising the following steps:  
       [0017] Sending the services control data from an end point to at least one intermediate station, as well as differentiating between local services control data, in other words data to be carried out in the intermediate station, and services control data to be passed farther along the signaling segment.  
       [0018] In addition, a method and a system for transmitting services control data are claimed, this transmission taking place from a first end point of a signaling segment, by way of a first network, to a gateway, and from the gateway, by way of a second network that is different from the first network, to the second end point of the signaling segment.  
       [0019] In this connection, the gateway packs the services control data received from the first end point into a data container that is adapted for transmission by way of the second network and carries out this transmission. 
     
    
    
     [0020] Other advantages, characteristics, and features of the present invention will now be explained in greater detail, on the basis of exemplary embodiments, making reference to the accompanying drawings.  
     [0021]FIG. 1 shows a configuration according to the invention, in which the DSS1 protocol, contrary to its original purpose of use, is used on a signaling segment that spans several stations,  
     [0022]FIG. 2 shows the position and the function of the services distributor as well as the protocol unit in an intermediate station,  
     [0023]FIG. 3 shows an exemplary configuration,  
     [0024]FIG. 4 shows the H.323 structure model according to the state of the art. 
    
    
     [0025]FIG. 1 shows a configuration according to the invention, in which the DSS1 protocol, contrary to its original purpose of use, is used on a signaling segment that spans several stations. There is at least one intermediate station  12  (which does not necessarily have to be physically separate from the end points) between the first end point  11  and the second end point  13 . The first end point  11  can be a switching center (EWSD), for example, and the second end point  13  can be another terminal (PC with telephony application according to Internet protocol).  
     [0026] Now the invention will be explained in detail: One possible method for controlling services data is the so-called Generic Functional Protocol integrated into the DSS1 protocol. The corresponding services control data are transmitted in so-called ROSE components (Remote Operation Service Element) within a special parameter (the Facility Information Element).  
     [0027] In this connection, there are four ROSE components: a request component (Invoke component), as well as three confirmation components (Return Result, Return Error, and Return Reject component). While the confirmation components only contain an identifier (Invoke ID) that makes the services request clear within the signaling connection, the invoke component additionally contains an operation code, by means of which each supplementary service receives a clear assignment.  
     [0028] The configuration shown in FIG. 1 is now supposed to behave in such a way, according to the invention, that services control data  14  transmitted from the first end point  11  are evaluated either by the second end point  13  or by local services programs  18  of the intermediate station  12 . Therefore, in case A, the services control data  14  must be distributed from the first end point  11  to the intermediate station  12  and, by means of a DSS1 message  15  that has been passed on, to the second end point  13 . In case B, the services control data  17  proceed from the second end point  13  and must be linked up with services control data from local services programs in the intermediate station  12 , and passed to the first end point  11  as an expanded DSS1 message  16 .  
     [0029] This scenario as just described presumes that the intermediate station  12  has the possibility of differentiating between services control data to be processed locally or in a remote manner, on the basis of their content, and of sending these data to the local processing unit  18  or the respective end point  11  or  13  as a function of this differentiation.  
     [0030] Such a method will now be described using FIG. 2. A unit for differentiating between services control data to be carried out locally and to be passed farther along the signaling segment  23 ,  24  is integrated into the intermediate station  12 . This unit is referred to as a services distributor  20  in the following.  
     [0031] The nomenclature used in the following is derived from the ROSE protocol, but can fundamentally also be applied to other methods for services control. Likewise, the services control data can also be transported by way of other transport mechanisms, other than the DSS1 Generic Functional Protocol.  
     [0032] In this connection, the configuration of the intermediate station  12  meets the following requirements:  
     [0033] In order to be able to configure the services distributor  20  clearly, all of the stations along the signaling segment  23 ,  24  that process the services control data must be configured in such a way that a specific service (identified by its operation code) is only carried out by a specific station.  
     [0034] In order to assure a clear distribution of the confirmations (which contain only the identifier (Invoke ID), as mentioned above) or, to put it differently, in order to be able to clearly assign a confirmation to a services request when the confirmation is received, the end points that send the services control data, or the intermediate stations, are configured in such a way that they use only identifiers (Invoke IDs) within a specific range. The identifier is sent by the party that sends the services request.  
     [0035] Within each intermediate station  12 , the operation codes of the services to be carried out locally, i.e., in the intermediate station  12 , and the range of the locally generated identifiers are stored in memory. Information about services not to be carried out locally does not have to be stored in memory in the intermediate station  12 .  
     [0036] As shown in FIG. 3, the services distributor  20  is coupled with a protocol control unit  19  of the intermediate station  12 . The protocol control unit  19  transfers all of the received services control data and any additional information, such as the direction and the transport mechanism in which the services control data were transported, to the services distributor  20 . The services distributor  20  determines, per services control data item, whether it is supposed to be passed farther along the signaling segment or whether the service is to be performed locally.  
     [0037] For example, the signaling message  23  contains the services control data that the services A and B are to be carried out by the second end point (not shown in FIG. 3), while the services V and X are to be carried out locally. The services distributor  20  recognizes this by the fact that the operation code of V and X is contained in a local services list  21 . The services control data to be processed locally can either be passed on by the services distributor  20  directly to the unit  22  that carries them out, or (provided with a special marking or in a special data region) can be given back to the protocol control unit  19 .  
     [0038] The services control data A and B, which must be passed farther along the signaling segment, are given back to the protocol control unit  19  and passed on by the latter in the form of a signaling message  24 .  
     [0039] If the services distributor  20  receives confirmations on the basis of services requests sent earlier, it determines whether or not the identifier contained in the confirmation was issued locally.  
     [0040] The services distributor is generally not needed for bringing together locally generated and received services information (i.e., guarantee of functionality in the opposite direction). Since no knowledge about the services is required in this case, it can be handled by the protocol control unit  19  on its own. However, it must be assured that the identifiers of the services control requests are in the range established previously, in order to allow a subsequent clear distribution of resulting confirmations.  
     [0041] If existing terminals that cannot be configured are used, it is generally not possible to restrict the ranges for the identifiers. In this case, the services distributor  20  must also be used for bringing together locally generated and received services data. In this connection, the identifiers of all services requests must be stored in memory together with their source (“local” or “remote”). If the same identifier already exists, because it was already assigned by another location, it must be changed to a value that has not been used yet, when the data are brought together, in order to assure that the identifiers are clear on the signaling segment  23 ,  24 . If the identifier was changed when the data were brought together, it must be reset to the original value during distribution. Confirmations received from the opposite direction must be sent using both information items, the identifier contained and the source of the services request.  
     [0042] In general, the method can be used in both directions of a signaling segment. However, if services control data are brought together only in one direction (as in FIG. 3, for example), the division of identifiers into non-overlapping ranges only has to take place in the one direction, and the distribution only has to take place in the opposite direction.  
     [0043]FIG. 3 shows an exemplary embodiment of the invention. All of the DSS1 supplementary services are supposed to be available to an H.323 client  29  (PC with IP telephony application). For this purpose, the switching system  25  (EWSD) must be expanded accordingly, with a new unit. The new unit, an H.323 gateway PCU (Peripheral Control Unit)  27 , corresponds to the intermediate station in the sense of the invention, while the EWSD core  26  and the H.323 client  29  are the end points. The transmission protocol being used is the DSS1 protocol.  
     [0044] The H.323 client  29  is therefore supposed to be able to understand the typical DSS1 services control data. For this purpose, the EWSD core  26  is configured for a DSS1 terminal (ISDN telephone). The H.323 gateway PC  27  packs the DSS1 message  28  received from the EWSD core  26  (with the exception of the services control data intended for the H.323 gateway PCU  27  itself) into a data container  30  that is suitable for transmission by way of an H.323 network.  
     [0045] This data container  30  is transmitted to the H. 323  client  29  in a suitable H.225 message  31  (H.225 Call Control Message).  
     [0046] The fact that the DDS1 protocol, which was actually developed for local signaling, is transported over several stations in this arrangement (from the EWSD core  26  directly to the H.323 gateway PCU  27  and from there in the container to the terminal of the H.323 client  29 ) is clearly evident.  
     [0047] However, a DSS1 message transmitted form the EWSD core  26  to the H.323 gateway PCU  27  can also contain services control data that serve for control of the H.323 gateway PCU  27  and therefore are not supposed to be transported to the H.323 client  29 . In order to assure this, a services distributor has to be integrated into the H.323 gateway PCU  27 . This works according to the method according to the invention, in that it recognizes what services control data are intended for the H.323 gateway PCU  27  and what data must be passed on to the H.323 client  29 , within the container.