Communications system

• US 20040028035A1
• Filed: 05/22/2003
• Published: 02/12/2004
• Est. Priority Date: 11/30/2000
• Status: Active Grant

• Current Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Original Assignee: Tandberg Telecom AS (Cisco Systems, Inc.)
• Inventors: Read, Stephen Michael
• Granted Patent: US 7,512,708 B2
• Time in Patent Office: Days
• US Class Current: 370/352
• CPC Class Codes: H04L 61/00 Network arrangements, protocols or services for addressing or naming
• CPC Class Codes: H04L 61/2514 between local and global IP addresses
• CPC Class Codes: H04L 61/2517 using port numbers
• CPC Class Codes: H04L 61/2535 Multiple local networks, e.g. resolving potential IP address conflicts
• CPC Class Codes: H04L 61/2564 for a higher-layer protocol, e.g. for session initiation protocol [SIP]
• CPC Class Codes: H04L 63/02 for separating internal from external traffic, e.g. firewalls
• CPC Class Codes: H04L 63/0281 Proxies
• CPC Class Codes: H04L 63/029 Firewall traversal, e.g. tunnelling or, creating pinholes
• CPC Class Codes: H04L 63/108 when the policy decisions are valid for a limited amount of time
• CPC Class Codes: H04L 65/1043 Gateway controllers, e.g. media gateway control protocol [MGCP] controllers
• CPC Class Codes: H04L 65/1101 Session protocols
• CPC Class Codes: H04L 65/1104 Session initiation protocol [SIP]
• CPC Class Codes: H04L 65/1106 Call signalling protocols; H.323 and related
• CPC Class Codes: H04L 67/14 Session management for real-time applications in data packet communications networks H04L65/1066
• CPC Class Codes: H04L 69/329 in the application layer [OSI layer 7]

Abstract

The present invention relates to a communications system (1) for handling communications sessions, for example multimedia calls or voice calls. The communications system (1) comprises a local terminal (10), an external server (40), a proxy interface agent (PIA) (11) between the terminal (10) and a shared network (20). The communication means includes a NAT function (32) through which the communications session must pass. The communications session is carried over the network (20) over one or more logical channels between the terminal (10) and the external server (40), during which the first NAT function (32) applies network address mappings on the terminal'"'"'s transport addresses (14). The PIA (11) acts on behalf of the terminal (10) in communications with the external server (40), and establishes a logical channel on an outbound connection to the server that serves as a control channel between the PIA (11) and the server (40). The PIA (11) establishes dynamic outbound connections to the server (40), and in response to a request from the server or in response to a request from the PIA itself (11), makes one or more associations between the terminal'"'"'s transport address(es) (14) and identifiable logical channel(s) between the PIA (11) and the server. These identifiable logical channel(s) are established on one or more of the dynamic outbound connections from the PIA (11) to the server (40).

Claims

1. A communications system for handling a communications session with a destination communication system, comprising a first local terminal, an external server, one or more logical channels between the first local terminal and the external server for carrying the communications session over a shared communications network, said communication means including a first NAT function through which the communications session must pass, in which:

i) the first local terminal has at least one transport address for the communications session;

ii) the first NAT function applies network address mappings on the transport addresses on connections between the first terminal and the shared communications network;

iii) the system includes a first proxy interface agent arranged to act on behalf of the first local terminal in communications with the external server;

iv) the first proxy interface agent is capable of establishing a logical channel on one or more outbound connections to the external server, said logical channel serving as a control channel between the first proxy interface agent and the external server;

wherein;

v) said outbound connections are dynamic outbound connections established by the first proxy interface agent;

vi) the first proxy interface agent is adapted to make association(s) between the transport address(es) of the first local terminal and identifiable logical channel(s) between the first proxy interface agent and the external server, said identifiable logical channel(s) being established on one or more of said dynamic outbound connections from the first proxy interface agent to the external server.

2. A method of handling a communications session in a communications system, the communications system comprising a first local terminal, an external server, a first proxy interface agent between the first local terminal and the shared network, said communication means including a first NAT function through which the communications session must pass, in which the method comprises the steps of:

i) carrying the communications session over a shared communications network over one or more logical channels between the first local terminal and the external server, the first local terminal having at least one transport address for the communications session;

ii) allowing the first NAT function to continue to apply network address mappings on the transport addresses on connections between the first terminal and the shared communications network;

iii) using the first proxy interface agent to act on behalf of the first local terminal in communications with the external server;

iv) using the first proxy interface agent to establish a logical channel on one or more outbound connections to the external server, said logical channel serving as a control channel between the first proxy interface agent and the external server;

wherein the method comprises the steps of;

v) using the first proxy interface agent to establish dynamic outbound connection(s) to the external server;

vi) using the first proxy interface agent to make one or more associations between the transport address(es) of the first local terminal and identifiable logical channel(s) between the first proxy interface agent and the external server, said identifiable logical channel(s) being established on one or more of said dynamic outbound connections from the first proxy interface agent to the external server.

3. The method of claim 2, in which the first proxy interface agent makes said associations in response to a request from the external server.

4. The method of claim 2, in which the first proxy interface agent makes said associations in response to a request generated by the first proxy interface agent itself.

5. The method of claim 2, in which the external server itself (or alternatively the first proxy interface agent) is adapted to request the external server to make associations between the said identifiable logical(s) channels and the logical channels of communication with a destination communication system such as a destination terminal.

6. The method of claim 2, in which the communications system includes a client-server protocol on the control channel

wherein:

i) the client-server protocol on the control channel is used to enable the dynamic association of (a) logical channels of communication used by the first terminal, with (b) identifiable logical channel(s) between the first proxy interface agent and the external server, said identifiable logical channel(s) being established on one or more of said dynamic outbound connections from the first proxy interface agent to the external server, with (c) logical channels of communication between the external server and a destination communication system, resulting in the appearance that the first terminal is located at transport addresses on the external server and the destination communication system is at the first proxy interface transport addresses.

7. The method of claim 6, in which the external server is adapted to be master of the client-server protocol and also to modify the transport addresses being carried in the real-time (or non-real-time) protocol, in order that the first terminal communicates with the first proxy interface agent as if it were a destination communications system, and the destination communications system communicates with the external server as if it were the first terminal.

8. The method of claim 6, in which the first proxy interface agent is adapted to be master of the client-server protocol and also to modify the transport addresses being carried in the real-time (or non-real-time) protocol, in order that the first terminal communicates with the first proxy interface agent as if it were the destination communications system, and the destination communications system communicates with the external server as if it were the first terminal.

9. The method of claim 2, in which the transport address(es) of the first local terminal are assigned dynamically.

10. The method of claim 2, in which the transport address(es) of the external server are assigned dynamically.

11. The method of claim 2, in which none of the transport address(es) of the external server are assigned dynamically.

12. The method of claim 2, in which the communications system includes a first firewall through which the communications session must pass, the first firewall being configured to restrict certain types of communication between the first local terminal and the shared communications network and being configured not to restrict communication between the first proxy interface agent and the external server.

13. The method of claim 2, in which at least one of the transport address(es) of the external server have at least one pre-assigned port, and the outbound connections from the first proxy interface agent to the external server uses said pre-assigned port(s).

14. A method as claimed in claim 13, in which all the transport address(es) of the external server have pre-assigned ports.

15. The method of claim 14, in which all the transport address(es) of the external server have at most two pre-assigned ports.

16. The method of claim 2, in which all the transport address(es) of the proxy interface agent are assigned dynamically.

17. The method of claim 2, in which at least one of the transport address(es) of the proxy interface agent uses pre-assigned ports.

18. The method of claim 2, in which all the transport address(es) of the proxy interface agent uses pre-assigned ports.

19. The method of claim 2, in which the communications system includes a second local terminal and the external server is a proxy server between the first terminal and the second terminal that acts for each terminal as a proxy for the other terminal during the course of the communications session.

20. The method of claim 2, in which the communications system includes a second local terminal and a second external server which acts as a proxy for the second terminal and communication between the first external server and the second external server is via a public network or a shared network.

21. The method of claim 2, in which the shared communications network includes the public communications network.

22. The method of claim 2, in which the shared communications network includes the Internet.

23. The method of claim 2, in which the proxy interface agent is co-located with the local terminal.

24. The method of claims 2, in which the proxy interface agent is remote from the local terminal.

25. The method of claim 2, in which there is more than one local terminal for the proxy interface agent.

26. The method of claim 2, in which the proxy interface agent simultaneously acts on behalf of terminals using different real-time and/or non-real-time protocols.

27. The method of claimed in any of claim 2, in which the external server simultaneously acts on behalf of terminals and/or proxy interface agents using different real-time and/or non-real-time protocols.