Abstract:
A method and program product for handling communications with stations in communications systems, especially digital telecommunications systems, such as for VoIP telephony. Requests are received for communicating with communications stations in the communications system. Each request is forwarded to a respective communications system station, which returns an indication of an intended response. Depending upon whether the intended response is appropriate, the proposed response may be forwarded to the requester. Otherwise, if the intended response is determined inappropriate, an indication is returned to the communications system station that the intended response is inappropriate.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention is related to communications systems and more particularly, to digital communications systems such as VoIP telecommunications systems. 
     2. Background Description 
     Commercial telecommunications platforms have allowed service providers to deliver Internet Protocol (IP) based telecommunications services. Typical such IP telecommunications services feature common channel telecommunications packet switching capabilities, such as Signaling System Number 7 (SS7) signaling capabilities. These capabilities allow for legacy feature support and, further, interconnection with Public Switched Telephone Networks (PSTN). Digital communications such as Voice over IP (VoIP), for example, normally use Session Initiation Protocol (SIP) for establishing and clearing of connections between network stations. VoIP calls using SIP work well for a relatively simple connection with simple user control, e.g., using a typical user interface. 
     However, some complex features have proven difficult to implement in VoIP using SIP, regardless of the user interface. For example, SIP has no provision for handling calls directed to unavailable locations, or calls forwarded to restricted access locations. Instead, these may be handled by the network communications server, on an ad hoc basis with spotty results. Unfortunately, such calls have a high likelihood of occurrence. 
     Thus, there is a need for flexibly adding features to Session Initiation Protocol (SIP) based systems and, more particularly, for a simple efficient way to add features, even complex features, to existing Voice over IP (VoIP) systems. 
     SUMMARY OF THE INVENTION 
     It is a purpose of the invention to expand the capabilities of existing communications systems; 
     It is another purpose of the invention to seamlessly add features to existing digital communications systems. 
     The present invention relates to a method and program product for handling communications with stations in communications systems, especially digital telecommunications systems, such as for VoIP telephony. Requests are received for communicating with communications stations in the communications system. Each request is forwarded to a respective communications system station, which returns an indication of an intended response. Depending upon whether the intended response is appropriate, the proposed response may be forwarded to the requester. Otherwise, if the intended response is determined inappropriate, an indication is returned to the communications system station that the intended response is inappropriate. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The foregoing and other objects, aspects and advantages will be better understood from the following detailed description of a preferred embodiment of the invention with reference to the drawings, in which: 
         FIG. 1  shows an example of a communications system according to a preferred embodiment of the present invention; 
         FIG. 2  shows an example of implementation of the present invention in a state of the art VoIP communications network, for communications between endpoints through applications server. 
     
    
    
     DESCRIPTION OF PREFERRED EMBODIMENTS 
     Turning now to the drawings and more particularly,  FIG. 1  shows an example of a communications system  100  including a digital call handling capable network  102 , according to a preferred embodiment of the present invention. Although shown as a local area network  102  handling Voice over Internet Protocol (VoIP) calls in this example, the network  102  may be any suitable network including, for example, the Internet. Further, in this telecommunications example, the system  100  includes a typical Internet Protocol (IP) Multimedia (IM) Subsystem or IMS bundle for interfacing multimedia information (e.g., voice and data) to a public switched telephone network/public land mobile network, PSTN/PLMN  104 , e.g., through a gateway  106 . Communications network stations  108 ,  110  may be devices that are connected directly to the network  102  (i.e., as an endpoint), or through a proxy  112 . Also, communications devices on the PSTN/PLMN  104 , e.g., a wirelessly connected handheld  114 , a cellular phone  116 , a modem connected personal computer (PC)  118 , and/or an analog/digital telephone  120 , connect through gateway  106 . One or more application server(s)  122  in the network  102  provide the preferred system  100  with telecommunications services features, e.g., voice features and e-mail. Preferably, the applications server  122  is a Session Initiation Protocol (SIP) applications server. It should be noted that although described herein in terms of calls between the network  102 , gateway  106 , proxy  112 , endpoints  108 ,  110  and telecommunications devices  114 - 120 , this is for example only and not intended as a limitation. 
     The SIP application server  122  handles communications links with and between network entities, i.e., network stations  108 ,  110 , and with telecommunications devices  114 - 120 , gateway  102 , proxy  112  and the network  102 . An equivalent state of the art system is normally equipped to handle most circumstances for which a response has been specifically provided (e.g., built in special features), but is otherwise unequipped to handle something out of the ordinary, new features or features newly added on the fly. However, endpoints  108 ,  110 , gateway  106 , and server  122  in a preferred embodiment telecommunications system  100  include a capability to create a special SIP message in response to any unexpected circumstances. The special SIP message or consultation message is referred to herein as a PERMISSION SIP message or simply a PERMISSION. The PERMISSION indicates a potential or intended response to the SIP application server  122  for the particular circumstances. 
     So, for example, upon commencement of an attempted link between network entities, the SIP application server  122  receives a request from one initiating endpoint or gateway, and originates a request to another, receiving endpoint. The receiving endpoint creates the PERMISSION that includes an intended response, or at least a partial indication of a response to the initiating endpoint, which is returned to the SIP application server  122 . The SIP application server  122  determines from the PERMISSION whether the intended response is appropriate/authorized for the corresponding initiating endpoint, e.g., forwarding an incoming call from the initiating endpoint to another station. If the response is authorized, the receiving endpoint generates the desired response message, forwarding the incoming call in this example. Otherwise, the response is unauthorized and, instead of having no predetermined/preselected response available, the PERMISSION may provide the SIP application server  122  with an appropriate alternate response. Thus, by including PERMISSION SIP messages, the system can implement complex features, even in a system where no such provision has been made to accommodate, much less make available those complex features and even without requiring a user interface to implement the features or handle feature requests interactively. 
     In another general example with reference to  FIG. 1 , communications begins as a message originating from one initiating endpoint, e.g., from telephone  120  on PLMN/PSTN  104  at gateway  106 , is directed to a second, e.g., through application server  122  to a user identified with digital telephone  110  at proxy  112 . In this example, the user at digital telephone  110  has the do not disturb feature selected. According to a preferred embodiment of the present invention, endpoint  110  responds with a PERMISSION, which is returned through proxy  112  to the application server  122 . The PERMISSION includes an intended response from the endpoint  110 . The applications server  122  analyzes the PERMISSION and determines an appropriate action that depends upon the contents of the PERMISSION. So, for this example, if the application server  122  determines that the endpoint  112  is allowed to send the desired message (refuse the call), the application server  122  grants the request by sending a positive acknowledgement back to endpoint  110 . The endpoint  110  then generates the response to refuse the call to application server  122 . The applications server  122  forwards the response to endpoint  106 , which takes an appropriate action, e.g., sends a busy tone. Otherwise, if the applications server  122  determines from the PERMISSION that the response is not authorized, the applications server  122  responds to the endpoint  110  with a “403 Forbidden” SIP message, for example. So, instead of sending the response to refuse the connection, the call continues to ring at the network station. 
       FIG. 2  shows an example of an implementation of the present invention in a state of the art VoIP communications network, for communications between gateway  106  and endpoint  108  through an applications server  122 , e.g, as in the network  102  of  FIG. 1  with like elements labeled identically. The applications server  122  may be implemented, for example, in a hiQ 8000 VoIP Softswitch/Media Gateway Controller (MGC) from Siemens Corporation. So for this example, an incoming call through gateway  106  initiates a connection to endpoint  108  by sending an INVITE message  130  to applications server  122 . At  132 , the application server  122  both acknowledges receiving the INVITE with a “100 Trying” message and generates a new INVITE to endpoint  108 . The endpoint  108  responds at  134  by returning a “100 Trying” message to the applications server  122 . In this example, the user for digital telephone endpoint  108  has “call forwarding on ring no answer” active at the endpoint. At  136  the endpoint  108  follows with a “180 Ringing” response and starts a timer. At  138  the applications server  122  forwards the “180 Ringing” response to the gateway  106 . When the timer expires at  140 , endpoint  108  sends a “PERMISSION 302” that describes the potential (i.e., if permitted) response. So, the PERMISSION may be for a “302 Moved Temporarily” message which requests that incoming calls be forwarded to a given destination. However, before forwarding the call, the applications server  122  analyzes the PERMISSION and verifies whether the call to endpoint  108  may be forwarded to the designated destination. When the application server  122  receives the PERMISSION message, it determines from a local (to the server) database if the endpoint is allowed to forward the call to the desired destination. 
     If the applications server  122  determines that the intended response is appropriate, the applications server  122  returns a “200 OK” SIP message (not shown) and the endpoint  108  sends the “302 Moved Temporarily” message to request the call to be handled normally, forwarded in this example. When, however, the verification indicates that the endpoint is not allowed to forward to the desired destination (e.g., international), the applications server  122  declines the PERMISSION at  142  by returning a “603 Decline” or a “403 Forbidden” message to endpoint  108 . As a result, the endpoint  108  receives an indication that the message was not allowed to be forwarded. So, instead of forwarding, the call continues to ring at the digital telephone endpoint  108 , e.g., until Voice Mail answers. 
     By contrast, previously upon timer expiration, the destination endpoint returned the “302 Moved Temporarily” message to the applications server. However, a problem occurred whenever the initiating endpoint was not allowed or not intended to connect to the forwarded destination. There was no SIP response message for refusing to forward the connection. Consequently, the applications server had no way of refusing the forward request. The present invention overcomes this shortfall in the prior art. 
     Advantageously, the present invention provides a simple elegant solution to this problem and expands the capabilities of existing communications systems. Further, the present invention may be applied to any digital communications system, regardless of protocol. 
     While the invention has been described in terms of preferred embodiments, those skilled in the art will recognize that the invention can be practiced with modification within the spirit and scope of the appended claims. It is intended that all such variations and modifications fall within the scope of the appended claims. Examples and drawings are, accordingly, to be regarded as illustrative rather than restrictive.