HK1050599A - Method of and system for extending internet telephony over virtual private network direct access lines - Google Patents

Description

Method and system for extending internet telephony over virtual private network direct access lines

Technical Field

The present invention relates generally to the field of virtual private networks, and more particularly to a method and system for providing a virtual private network in which a portion of each call is transmitted over an internet protocol network.

Background

Some larger organizations with widespread sites and venues use Virtual Private Networks (VPNs) as an alternative to traditional long distance services for their internal organization of telephone communications. Although virtual private networks are built into public switched telephone systems, they provide a communication system that is intended to be private from the user.

Referring to fig. 1, a simplified virtual private network block diagram is shown. An internal telephone system includes a plurality of telephones 11 operatively connected to a private branch exchange (PBX) 13. As is well known to those skilled in the art, several or even several stemona telephones are operatively connected to the PBX 13.

PBX13 provides intra-site communications between the phone and other phones in the site. Alternatively, the user of telephone 11 may make local and long distance calls outside a particular area by entering a number, such as "9," to obtain outside lines. Alternatively, the user of telephone 11 may make a VPN call by entering another number, such as "8", to contact members of the organization in other areas. Other areas may be a separate city, state, or even a country. Typically, the VPN number is in the form of a local seven digit telephone number. A three digit prefix number identifies an area and the remaining four digits identify a phone in that area.

In the embodiment of fig. 1, a user of telephone 11 who is located in a particular area, such as california, wants to make a VPN call to telephone 15, telephone 15 is located at a site in the organization, such as new york. The telephone 15 at the new york site is operatively connected to a PBX17 serving the site. For ease of illustration, the VPN number associated with phone 15 is 555-1234. To initiate a call, the user takes the telephone 11 off-hook and receives a dial tone from the PBX 13. The user input of "8" identifies the call as a VPN call and receives another dial tone. The user then enters the numbers 555-1234. PBX13 forwards the call to switch 19 of Public Switched Telephone Network (PSTN)21 via direct access line (DAL 23). The switch 19 is identified in the PSTN21 by a unique initial switch identifier (OSID). DAL23 is identified by an initial switching group (OTG) identifier. When the switch 19 receives the digits dialed on DAL23, it must reference a Service Control Point (SCP)25 for routing instructions. SCP25 uses the OSID and OTG to determine the identity of the VPN client and provides a routing indication to switch 19 based on the client identifier and the dialed number. The switch 19 routes the call to the appropriate terminating switch 27 via the PSTN 21. Switch 27 is operatively connected to PBX17 to complete a call to telephone 15.

One problem with VPN services is that public switched telephone systems cannot reliably extend to all parts of the world. Due to the unreliability of the PSTN in some parts of the world, particularly where organizations are located, those in developing countries, cannot use VPN services.

More recently, organizations have begun to establish and use packet-switched data networks, such as private intranets for crisis communication tasks and the internet itself. Organizations have established and accessed robust high-speed data networks for the purpose of transmitting data and electronic communications such as e-mail between areas, even in areas where reliable access to the public switched telephone system is not available.

Summary of The Invention

It is an object of the present invention to provide a system for extending VPN services over a data network such as a separate intranet and the internet.

The present invention provides a Virtual Private Network (VPN) that includes an Internet Protocol (IP) network and a Public Switched Telephone Network (PSTN). An egress (egress) enterprise gateway is operatively connected to the IP network. The egress enterprise gateway is operatively connected to the switches of the PSTN by a Direct Access Line (DAL). The setup signal for the virtual private network call and its call itself are transmitted over the IP network and the PSTN through the DAL. A smart tier in the IP network has the capability to route IP network initial calls to a conventional PSTN DAL.

Drawings

Fig. 1 is a block diagram illustrating a prior art virtual private network.

Fig. 2 is a block diagram illustrating a virtual private network in accordance with the present invention.

Fig. 3 is a block diagram illustrating the operation of an enterprise gateway in accordance with the present invention.

Detailed description of the invention

Referring now to fig. 2, a VPN in accordance with the present invention is indicated generally by the numeral 31. A portion of VPN31 is implemented in a conventional PSTN environment. The PSTN portion of network 31 includes a switch 33 that is served by SCP 35. Switch 33 is operatively connected to PSTN37, which in turn is operatively connected to switch 39, PSTN 37. Switch 39 is operatively connected to PBX41 at one location of the organization through DAL 45. PBX41 is operatively connected to a plurality of telephones, only one telephone 43 being shown.

Portions of VPN31 are also implemented in an IP network environment in accordance with the present invention. The IP network environment of the VPN31 includes an IP network, generally indicated by the numeral 47. The IP network 47 may comprise a private intranet, the internet, or a combination of a private intranet and the internet. The IP network 47 provides conventional internet and Web-based services as well as IP telephony services.

A local organization's telephone system includes a PBX51 and a plurality of telephones, only one of which, telephone 53, is shown. The telephone 53 operates in the normal manner. The user may use telephone 53 in PBX51 to call other telephone extensions. PBX51 may also provide an out-of-line telephone 53 through which users may make local and long distance calls.

In accordance with the present invention, a user may make a VPN call using telephone 53 and PBX 51. The PBX51 is operatively connected to an import Enterprise Gateway (EG) 55. Although gateway 55 is labeled as an "import" EG, it is a two-way EG and the label "import" is used only to identify the flow of calls with respect to telephone 53 to telephone 43. Referring to fig. 3, EG55 includes a signal gateway 57 and a media gateway 59. The signal gateway 57 provides a two-way protocol translation from a telephony signal protocol, such as SS7ISDN, or a channel association protocol (CAS) which relies on the signal protocol used by the PBX51, to an internet telephony signal protocol, such as Session Initiation Protocol (SIP) or h.323. The preferred embodiment of the present invention is based on the SIP signaling protocol. However, other embodiments are contemplated based on other protocols such as h.323. Media gateway 59 provides bi-directional protocol translation between traditional telephony time division multiplexed voice lines to IP transport protocols such as real-time transport protocol (RTP). In the case of ISDN or SS7 signals, the signal gateway 57 is connected to the PBX59 via an SS7 signal link or an ISDN D-channel signal link. In the case of a CAS signal, signal gateway 57 receives signal information from media gateway 59.

The SIP and RTP packets are transmitted over the IP network 47 to the egress enterprise gateway EG 61. Although gateway 55 is labeled as an "import" EG, it is a two-way EG and the label "import" is used only to identify the flow of calls with respect to telephone 53 to telephone 43. EG61 includes a signal gateway 63 and a media gateway 65. Signal gateway 63 and media gateway 65 perform bi-directional protocol interpretation in the manner described for signal gateway 57 and media gateway 59, respectively. Referring again to fig. 2, EG61 is connected to switch 33 of the PSTN through DAL 23.

Referring again to fig. 2, a VPN call may be generated from a telephone 53 located in, for example, the maryland island to a telephone 43 located in, for example, new york. The user takes the phone 53 off-hook and dials the VPN number in the normal manner. For example, the user dials 8777-4321. The PBX51 sends a normal setup message to the EG55 along with the dialed digits 777-4321. EG55 performs protocol translation and sets forth one such form of SIP invite message:

INVITE：7774321@xyzus.com

FROM：5551234@xyzmalaysia.com

TO：7774321@xyzus.com

in a preferred embodiment, SIP URLs are in the form of "telephone _ number @ gateway". Thus, EG55 is identified as xyz laysia.com and EG61 is identified as xyz. The SIP invite message is transmitted 47 to the EG61 over the IP network. The EG61 performs protocol translation and sends a setup message for the VPN number 777-4321 to the switch 33 via the DAL 23. The switch 33 recognizes the call as a VPN call and considers the SCP35 for routing instructions. The SCP35 uses the dialed digits, the OSID of the switch 33, and the OTG of the DAL23 to provide routing instructions to the switch 33. Based on instructions received from SCP35, a call is established from PSTN37 to telephone 43 with normal telephone signals. During call setup, the egress enterprise gateway 61 transmits an IP telephony signal back to the ingress enterprise gateway 55 over the IP network 47.

The system of the present invention also provides VPN services that originate from telephone 43 served by PSTN37 to telephone 53 served by IP network 47. The user takes phone 43 off-hook and dials the VPN number, e.g. the user dials 8-555-1234. PBX51 sends a setup message to switch 39 via DAL45 along with dialed digits 555-1234. The switch 39 recognizes the call as a VPN call and considers the SCP63 for the path selection instruction. The SCP63 provides path selection instructions to the switch 39 using the dialed digits, the OSID of the switch 39, and the OTG of the DAL 45. Upon receipt of the command from the SCP63, the switch 39 sends an SS7 initial address Information (IAM) to the switch 33. The switch 33 sends a setup message to the EG 61. EG61 performs protocol translation and sets forth this form of SIP invite information:

INVITE：5551234@xyzmalaysia.com

FROM：774321@xyzus.com

TO：5551234@xyzmalaysia.com

the SIP invite message is transmitted over IP network 47 to enterprise gateway 55. EG55 performs protocol translation and sends a setup message for VPN number 555-1234 to PBX 51.

From the foregoing, it can be seen that the present invention extends the architecture and infrastructure of a virtual private network using IP telephony to the extent that the PSTN is not reliably accessible. A portion of the call is established and transported through the IP network using the intelligent layer, which routes the call and its signals to the appropriate enterprise gateway. A portion of the call is established and transported over the PSTN using conventional VPN infrastructure. In addition, the present invention may be used to provide virtual private network services to internet appliances and devices such as IP phone 65 and IP phone enabled personal computer 67.

The present invention has been illustrated and described in accordance with a presently preferred embodiment. Those skilled in the art will appreciate that alternative embodiments will provide the benefit of the foregoing disclosure. Accordingly, the foregoing disclosure is intended to be illustrative, but not limiting.

Thus, the present invention has been fully described by way of example with reference to the accompanying drawings, it being readily understood that various changes and modifications may be made to the invention and any exemplary embodiments shown and/or described herein without departing from the spirit or scope of the invention as defined in the appended claims.

Claims (17)

1. A virtual private network comprising:

an internet protocol network;

an enterprise gateway operatively connected to said internet protocol network;

a direct access line operatively connected to said gateway; and

a switch operatively connected to the public switched telephone network of the direct access line.

2. The virtual private network as recited in claim 1, wherein the gateway comprises:

a signal gateway; and

a media gateway.

3. A virtual private network as claimed in claim 2 wherein said signal gateway comprises means for converting internet protocol call setup messages to telephony call setup messages.

4. A virtual private network as claimed in claim 2 wherein said signal gateway includes means for converting internet session initiation protocol information to a telephone call setup message.

5. The virtual private network as recited in claim 1, comprising:

a second enterprise gateway operatively connected to said internet protocol network; and

an initial public branch switch operatively connected to the second gateway.

6. The virtual private network as claimed in claim 5, wherein said second gateway comprises:

a signal gateway; and

a media gateway.

7. The virtual private network as claimed in claim 6, wherein said signal gateway of said second gateway comprises means for converting a telephone call setup message to an internet protocol call setup message.

8. The virtual private network as claimed in claim 6, wherein said signal gateway of said second gateway includes a device for converting telephone call setup messages to internet session protocol information.

9. The virtual private network as recited in claim 1, comprising:

a terminating private branch exchange operatively connected to said public switched telephone network.

10. A method of providing a virtual private network service, comprising the steps of:

transmitting a called party number to an enterprise gateway over an internet protocol network; and

the called party number is transmitted from the gateway to a switch of the public switched telephone network via a direct access line.

11. The method as in claim 10, wherein the public switched telephone network switch is defined by an initial switch ID (OSID).

12. The method as recited in claim 11, wherein the direct access lines are defined by an initial backbone group (OTG) definer.

13. The method as recited in claim 12, comprising the steps of:

sending a call over the public switched telephone network based on the called party number, the OSID, and the OTG.

14. The method as recited in claim 10 wherein said step of transmitting said called party number to said gateway comprises:

receiving the called party number at a second enterprise gateway in a telephony signal protocol; and are

The called party number is protocol converted from the telephone signal to an internet protocol transmitted over the internet protocol network.

15. The method as recited in claim 14, comprising the steps of:

generating a URL with the called party number at the second gateway.

16. The method as in claim 15 wherein said URL includes said called party number and a domain name corresponding to said gateway.

17. The method as in claim 10, wherein said step of transmitting said called party number to said gateway over said internet protocol network comprises:

sending a session initiation protocol INVITE message including the called party number to the gateway.