Providing telephony services to terminals behind a firewall and/or a network address translator

Abstract

A method and apparatus for allowing telephony or other types of media communications and services to be provided for a device ( 24 ) having a private network address that resides behind a firewall and network address and port translation (NAPT) module (which is unaware of the underlying protocol for the communications and services). Examples of the underlying protocol includes the Session Initiation Protocol (SIP) and Real-Time Protocol (RTP). A path through the firewall and NAPT module is defined by use of keep-alive messages communicated through the firewall and NAPT module. Addresses that are allocated by the firewall and NAPT module are associated with the device ( 24 ) for both signaling and media communications. A feature of the firewall that enables the provision of telephony and media communications through the firewall that is protocol-unaware is that the firewall allows responses to messages initiated by the device back through the firewall.

What is claimed is: 
     
         1 . A method for communications involving a first terminal coupled to a first side of a firewall and network address translator, the method comprising:
 receiving, at a node on a second side of the firewall and network address translator, a first message initiated by the first terminal, the first message identifying the first terminal to the node and indicating that the first terminal is available for a call session;   sending a second message from the node toward the first terminal, the first message and the second message causing creation of a signaling connection through the firewall and network address translator and creation of a mapping between a first address of the first terminal and a second address of the first terminal, where the first address is an address assigned to the first terminal on the first side of the firewall and network address translator, and where the second address is an address assigned to the first terminal on the second side of the firewall and network address translator; and   repeatedly sending keep-alive messages to maintain the mapping at the firewall and network address translator.   
     
     
         2 . The method of  claim 1 , wherein the keep-alive messages maintain the existing signaling connection through the firewall and network address translator to thereby maintain the mapping at the firewall and network address translator. 
     
     
         3 . The method of  claim 1 , further comprising:
 receiving a communication session request from the first terminal through the firewall and network address translator using the mapping maintained at the firewall and network address translator; and   initiating establishment of a call communication session with a second terminal using a call communication session connection.   
     
     
         4 . The method of  claim 3 , wherein receiving the communication session request from the first terminal through the firewall and network address translator using the mapping maintained at the firewall and network address translator comprises receiving the communication session request from the first terminal over the existing signaling connection maintained through the firewall and network address translator. 
     
     
         5 . The method of  claim 3 , wherein the call communication session connection is different from the existing signaling connection. 
     
     
         6 . The method of  claim 3 , wherein the call communication session is established under control of the node. 
     
     
         7 . The method of  claim 3 , wherein:
 the first message comprises an identifier of the first terminal and an external address assigned to the first terminal at the firewall and network address translator;   the method further comprises creating at the node an association between the identifier of the first terminal and the external address assigned to the first terminal by the firewall and network address translator; and   initiating establishment of the call communication session comprises communicating the association between the identifier of the first terminal and the external address assigned to the first terminal by the firewall and network address translator from the node to a media portal to enable the media portal to set up a media path between the first terminal and the second terminal via the firewall and network address translator.   
     
     
         8 . The method of  claim 1 , further comprising sending a communication session request toward the first terminal using the mapping maintained at the firewall and network address translator. 
     
     
         9 . The method of  claim 8 , wherein sending the communication session request toward the first terminal using the mapping maintained at the firewall and network address translator comprises sending the communication session request toward the first terminal over the existing signaling connection. 
     
     
         10 . The method of  claim 1 , wherein repeatedly sending the keep-alive messages to maintain the mapping at the firewall and network address translator comprises maintaining a timer and sending the keep-alive messages responsive to the timer. 
     
     
         11 . The method of  claim 10 , wherein the timer is maintained at the node and the keep-alive messages are sent from the node. 
     
     
         12 . The method of  claim 10 , wherein the keep-alive messages are sent by the node over the signaling connection. 
     
     
         13 . The method of  claim 1 , wherein repeatedly sending the keep-alive messages comprises sending the keep-alive messages at regular periodic time intervals. 
     
     
         14 . The method of  claim 1 , wherein the first message comprises an identifier of the first terminal and an external address assigned to the first terminal at the firewall and network address translator, the method further comprising creating at the node an association between the identifier of the first terminal and the external address assigned to the first terminal by the firewall and network address translator. 
     
     
         15 . The method of  claim 14 , wherein the first message comprises an indication that network address translation is active for the first terminal, and the node creates the association between the identifier of the first terminal and the external address assigned to the first terminal by the firewall and network address translator responsive to an indication that network address translation is active for the first terminal. 
     
     
         16 . The method of  claim 1 , wherein the signaling connection comprises a Session Initiation Protocol (SIP) signaling connection between the first terminal and the node. 
     
     
         17 . The method of  claim 1 , wherein receiving the first message comprises receiving a registration message requesting registration of the first terminal with the node. 
     
     
         18 . The method of  claim 17 , wherein:
 receiving the registration message comprises receiving a Session Initiation Protocol (SIP) REGISTER message; and   initiating establishment of a the first call communication session comprises sending a SIP INVITE message to a media portal.   
     
     
         19 . The method of  claim 18 , wherein the SIP REGISTER message comprises an identifier of the first terminal and an external address assigned to the first terminal at the firewall and network address translator, the method further comprising creating at the node an association between the identifier of the first terminal and the external address assigned to the first terminal by the firewall and network address translator. 
     
     
         20 . The method of  claim 19 , wherein the SIP INVITE message communicates the association between the identifier of the first terminal and the external address assigned to the first terminal by the firewall and network address translator from the node to the media portal to enable the media portal to set up a media path between the first terminal and the second terminal via the firewall and network address translator. 
     
     
         21 . The method of  claim 19 , wherein the SIP REGISTER message comprises a flag indicating that network address translation is active for the first terminal, and the node creates the association between the identifier of the first terminal and the external address assigned to the first terminal by the firewall and network address translator responsive to the indication that network address translation is active for the first terminal. 
     
     
         22 . The method of  claim 17 , wherein receiving the registration message comprises receiving the registration message at a SIP proxy. 
     
     
         23 . The method of  claim 22 , wherein the node comprises the SIP proxy. 
     
     
         24 . The method of  claim 1 , wherein:
 receiving the first message and sending the second message cause registration of the first terminal; and   repeatedly sending the keep-alive messages to maintain the mapping at the firewall and network address translator is performed for a duration of the registration of the first terminal.   
     
     
         25 . The method of  claim 1 , wherein the mapping comprises a mapping between an internal address of the first terminal and an external address assigned to the first terminal by the firewall and network address translator.