Method for providing ims support for enterprise pbx users

Abstract

An architecture and procedures by which an NGN can provide the following capabilities to an NGCN user: basic terminating service in the peering model; enhanced terminating services in the peering model; enhanced originating services in the peering model; and roaming service in the subscription and peering models. All capabilities are provided in an easily scalable manner via provisioned subscriber data and small modifications to existing IMS procedures. In one embodiment, an NGN is configured among the external networks to receive all SIP requests intended for the NGCN users of an NGCN interconnected to the NGN via the peering model (this NGN is the trunking home NGN), and the NGN forwards these requests to the NGCN for handling using request retargeting.

We claim: 
     
         1 . A method of providing roaming service for a user in a Next Generation Network (NGN), the method comprising:
 assigning to one or more users in a Next Generation Corporate Network (NGCN) a Session Internet Protocol (SIP) registrar name whose domain is assigned within a public Domain Name System (DNS) to a roaming home NGN; and   within a subscriber database, provisioning a public user identity (PUID) assigned to an NGCN user having roaming capability with an alternate registrar, wherein the alternate registrar contains an address at which the NGCN server can be reached with a registration request message.   
     
     
         2 . The method of  claim 2 , further comprising:
 receiving a registration request message for a particular PUID;   determining whether the particular PUID has roaming capability;   in response to determining the particular PUID has roaming capability,
 forwarding the alternate registrar instead of Serving Call Session Control Function (S-CSCF) data in a response message; 
 forwarding the registration request message to the address of the alternate registrar instead of an S-CSCF. 
   
     
     
         3 . The method of  claim 2 , further comprising a network server that forwards the registration request or response message populating one or more SIP path and service route headers in the registration request message and the response message according to standard SIP procedures so that a subsequent originating or terminating request message follows a same path between the alternate registrar in the NGCN and a roaming user. 
     
     
         4 . The method of  claim 2 , wherein the home domain provisioned in the public DNS to direct the registration request message to the roaming home NGN is instead provisioned within the DNS of the NGCN to direct the registration request directly to the alternate registrar within the NGCN when the NGCN user is receiving IP service within the NGCN. 
     
     
         5 . The method of  claim 2 , wherein the roaming home NGN comprises an Internet Protocol Multimedia Subsystem (IMS) that assigns the same entry point into the IMS for SIP registration request messages from roaming NGCN users and roaming NGN users being served in one or more visited NGNs, and wherein procedures followed by a visited NGN for handling roaming NGCN users and roaming NGN users are the same. 
     
     
         6 . The method of  claim 1 , further comprising:
 assigning to one or more users in a Next Generation Corporate Network (NGCN) a public user identity (PUID) that is known to a trunking home NGN and has a domain assigned to the trunking home NGN;   provisioning the subscriber database with an originating services flag representing profile data associated with the PUID of the one or more NGCN users whose NGCN is interconnected via a peering model and who is to receive enhanced originating services.   
     
     
         7 . The method of  claim 6 , further comprising:
 receiving an originating request message from a particular NGCN user having a PUID;   determining whether the originating request message from the particular NGCN user is a candidate for originating services according to a local policy;   in response to determining whether the originating request message from the particular NGCN user is a candidate for originating services, sending a query to a subscriber database using the PUID of the particular NGCN user;   forwarding the originating services flag for the PUID of the particular NGCN user in a response message to an Interrogating Call Session Control Function (I-CSCF);   determining whether the response message further comprises Serving Call Session Control Function (S-CSCF) information for the PUID of the particular NGCN user;   in response to determining whether the response message further comprises S-CSCF information for the PUID of the particular NGCN user, forwarding the request message to the appropriate S-CSCF.   
     
     
         8 . The method of  claim 7 , wherein the trunking home NGN comprises an IMS providing enhanced originating services to an NGCN user according to a peering model. 
     
     
         9 . The method of  claim 7 , wherein the local policy specifies that one more originating requests received at a specific IBCF or I-CSCF are candidates, or that requests from a specific NGCN server are candidates.