CN1295912C - Method for voice signal to break through firewall and network address converter - Google Patents

Abstract

The invention discloses a method for voice signaling to penetrate a firewall and NAT, comprising: a media gateway controller opens a general port for communication of VoIP messages; a voice access device sends a connection request to a designated port of the media gateway controller , and establish a channel for VoIP message transmission; the voice access device encapsulates the VoIP message to be sent into an ordinary communication message, and sends it to the media gateway controller through the channel; the media gateway controller receives the message from the channel After the message is decapsulated, it is transferred to the corresponding message processing module for processing according to the value of the message type field. The invention enables UDP messages such as MGCP, SIP, and RTP to smoothly penetrate NAT and firewalls, so that IP voice services can be provided in places where IP voice communications through NAT and firewall devices can access the Internet, and can be realized under complex network conditions. IP voice access, you can make calls wherever you can access the Internet.

Description

Method for Voice Signaling to Penetrate Firewall and Network Address Translator

technical field

The invention relates to a method for voice signaling to penetrate a firewall and a Network Address Translator (NAT), in particular to a method for tunnel-based voice signaling to penetrate a firewall and a NAT.

Background technique

Although the traditional public telephone network PSTN (Public Switched Telephone Network) based on time division multiplexing TDM (Time Division Multiplexer) can provide 64kbit/s (based on 2M link) business, the business and control are all completed by the switch. PSTN can guarantee excellent voice quality, but the operation of providing new services is relatively complicated and requires a long cycle, which makes operators feel powerless under the fierce competition of modern enterprises. At the same time, the development of computer technology and the increasing demand for computer interconnection have made IP-based packet switching data networks widely used, and the resource utilization rate of IP networks is relatively high. IP technology has been widely used in data and voice communication, and has become an important technology in the field of modern communication.

The large scale of digital signal processor DSP (digital sigral processors) makes it possible for IP voice communication to move towards the large-scale application of telecommunication level. DSP can be used in voice codecs and high-speed modems. The specific operating instructions of digital signal processors and their high-speed performance provide powerful support for technological applications that were unimaginable just a few years ago. Now DSP can be produced on a large scale, and the price is getting cheaper, the performance is getting higher and higher, and the function is getting more and more powerful. Exploration has finally led to the large-scale application of IP voice equipment based on DSP and IP technology in the field of communication.

Since the IP protocol exists in a large number of network servers, workstations, and network equipment, it is logical to become a convenient platform for supporting multimedia communication services.

IP is the bearing part of VoIP (Voice over IP) related communication messages, and the VoIP platform is a collection of many technologies and protocols. IP and real-time protocol RTP (Real Time Protocol), media gateway control protocol MGCP (MediaGateway Control Protocol), resource reservation protocol RSVP (Resource Reservation Protocol), H.323 (H.323 is one of the important standards of ITU multimedia communication series standards One, the aspect of concern is video conferencing) and other protocols together provide a VoIP multimedia communication platform for modern communications. IP voice access devices include MGCP (MediaGateway Control Protocol) terminals, SIP (Session Initiation Protocol) telephones, H.323 terminals, etc., all of which are based on different VoIP control signaling.

In the field of VoIP communication, the basic components include the media gateway controller MGC (the media gateway controller can be a soft switch device, a call agent, a relay control gateway, or other media gateway controllers), an access gateway AG ( Access Gateway) and integrated access device IAD (Integrated Access Device), where the difference between IAD and AG is that AG only provides media access services such as voice, while IAD also provides data access services in addition to voice access services).

Signaling and voice flow are exchanged between media gateway control and IP voice access equipment through IP protocol to complete multimedia communication such as voice.

Due to the shortage of IP addresses and the consideration of network security by network users, they generally need to establish their own private network, and set up NAT devices between the private network and the public network to complete the data exchange between the public and private networks. At the same time, a firewall is set up between the public network and the private network to allow only specific packets of specific protocols to pass through. The structure is shown in Figure 1. The network devices in the private network can obtain external domain name query services, and can access the WWW (World Wide Web) server based on the Hypertext Transport Protocol HTTP (Hypertext Transport Protocol). However, in the field of IP voice communication, signaling and voice are separated, and the address and port information of voice data exchange are transmitted through signaling. Since firewalls and NAT devices cannot understand IP voice communication signaling messages, VoIP-based voice Such as multimedia communication cannot be carried out in such a network. The core of the NAT device is to replace the address and port of the message so that it can be effectively transmitted between different networks. The working principle of the NAT device is shown in Figure 2. But this device hinders the application of IP voice technology in such networks.

Contents of the invention

For the existing problems and deficiencies in the above-mentioned existing voice message transmission, the purpose of the present invention is to provide a kind of VoIP message that can make VoIP signaling (MGCP, SIP, MEGACO etc.), RTP/RTCP etc. can penetrate NAT smoothly. and firewall methods.

The present invention is achieved in that a method for voice signaling to penetrate a firewall and a network address translator NAT comprises the following steps,

1), the media gateway controller opens a general-purpose port, is used for the communication of VoIP message;

2), the voice access device sends a connection request to the designated port of the media gateway controller, and establishes a channel for VoIP message transmission with it;

3), after the voice access equipment loads the VoIP message to be sent with the header of the VoIP message type mark, then the header and the VoIP message content of the VoIP message type mark are encapsulated in the data area of the general port transmission message And this VoIP message is encapsulated into common communication message, sends to media gateway controller from above-mentioned channel;

4) After the media gateway controller receives the message from the above channel, it decapsulates it, and transfers it to the corresponding message processing module for processing according to the value of the message type field.

Further, the media gateway controller processes the received message specifically according to the situation of the receiver at the opposite end, if the opposite end is a traditional voice access device, the voice message is directly sent according to the signaling information; if If the peer voice access device is connected to a NAT device, it will repackage the message and send it.

Further, the method also includes that the voice access device regularly sends a handshake frame of the tunnel protocol to the media gateway controller to ensure that the NAT and firewall paths can be maintained; at the same time, the voice access device is maintained in the media gateway controller activity status.

Further, the general port opened by the media gateway controller is specifically a UDP port or a TCP port.

The invention encapsulates the VoIP signaling that cannot be understood by firewalls and NAT devices into ordinary messages by opening a common protocol communication (UDP, TCP, DNS, HTTP, etc.) port on the media gateway controller. In this way, NAT and firewall devices do not need to understand the specific meaning of control messages such as signaling, but only need to forward or pass legal messages according to the original rules. The present invention can ensure that the existing routers, switches and NATs can solve the above problems without any upgrade and replacement. Make MGCP, SIP, MEGACO, RTP and other messages can smoothly penetrate NAT and firewall. Then establish a corresponding handshake relationship to realize communication between IP voice access devices.

The present invention enables UDP messages such as MGCP, SIP, MEGACO, and RTP to smoothly penetrate NAT and firewalls, so that IP voice services can be provided where IP voice communications through NAT and firewall equipment can access the Internet, thereby realizing IP voice access under complex network conditions, you can make calls wherever you can access the Internet.

Description of drawings

The present invention will be described in detail below in conjunction with the accompanying drawings.

Figure 1 is a schematic diagram of common networking of NAT and firewall devices between networks;

FIG. 2 is a schematic diagram of the working principle of the NAT device;

Fig. 3 is a schematic diagram of the communication principle of the present invention;

Figure 4 is a schematic diagram of packet encapsulation.

Detailed ways

Due to the shortage of IP addresses and the consideration of network security by network users, they generally need to establish their own private network, and set up NAT devices between the private network and the public network to complete the data exchange between the public and private networks. The access mode of the IP voice access device at this time is shown in Figure 3, multiple IP voice access devices (AG) are connected to the NAT, and the NAT is directly connected to the MGC; when communicating, the media gateway controller opens a common port , used for VoIP message communication; the voice access device sends a connection request to the designated port of the media gateway controller, and establishes a channel for VoIP message transmission; the voice access device loads the VoIP message to be sent with the VoIP type flag After receiving the message from the above channel, the media gateway controller decapsulates it and converts it according to the value of the message type field. into the corresponding message processing module for processing. The voice access device regularly sends tunnel protocol handshake frames to the media gateway controller to ensure that the NAT and firewall paths can be maintained; at the same time, the voice access device maintains an active state in the media gateway controller. In the figure, the thin double-arrowed line indicates the VoIP signaling channel, the thick double-arrowed line indicates the VoIP and RTP voice flow channel; the quadrilateral indicates the dedicated communication channel established between the AG and the MGC.

The MGC opens a UDP port 53 (DNS) as a communication port; the IP voice access device sends a connection request message to the port opened by the MGC, and establishes a communication channel between the IP voice access device and the MGC; the voice access device Sending handshake frames of the tunnel protocol to the media gateway controller regularly to ensure that the NAT and firewall channels can be maintained; at the same time, maintaining the active state of the voice access device in the media gateway controller. All messages transmitted between the MGC and the IP voice access device are transmitted through the channel established between them, that is, the VoIP voice message is encapsulated into the UDP protocol, specifically, the VoIP message is marked with the VoIP message type Header, and then encapsulate the message flag header and VoIP message content in the data area of the message transmitted by the UDP port, as shown in Figure 4. In this way, the NAT and the firewall will release the newly encapsulated message. When the MGC receives the message, it will decapsulate it, and according to the type of the VoIP voice message it carries, the corresponding MGCP message and/or RTP message The text is sent to the corresponding module for processing; if the opposite end is directly a voice access device, then according to the signaling information, the MGCP message and/or RTP message is directly sent to the corresponding port of the opposite end IP voice access device; If the opposite end also has a NAT and firewall structure, according to the port conditions of the opposite end, the packet is re-encapsulated and sent to the corresponding port, and the opposite end MGC performs corresponding processing and distribution, and then they can communicate with each other.

The communication port opened by the MGC of the present invention is a general-purpose port, such as a UDP port, a TCP port and other general-purpose IP message ports.

Claims (4)

1. A method for voice signaling to penetrate a firewall and a network address translator NAT, comprising the following steps, 1), the media gateway controller opens a general-purpose port, is used for the communication of VoIP message; 2), the voice access device sends a connection request to the designated port of the media gateway controller, and establishes a channel for VoIP message transmission with it; 3), after the voice access equipment loads the VoIP message to be sent with the header of the VoIP message type mark, then the header and the VoIP message content of the VoIP message type mark are encapsulated in the data area of the general port transmission message And this VoIP message is encapsulated into common communication message, sends to media gateway controller from above-mentioned channel; 4) After the media gateway controller receives the message from the above channel, it decapsulates it, and transfers it to the corresponding message processing module for processing according to the value of the message type field. 2. The method for voice signaling to penetrate through a firewall and a network address translator NAT as claimed in claim 1, wherein the media gateway controller processes the received message specifically according to the situation of the opposite receiver , if the opposite end is a traditional voice access device, the voice packet will be sent directly according to the signaling information; if the opposite end voice access device is connected to a NAT device, the packet will be repackaged and sent. 3. The method for voice signaling to penetrate through a firewall and a network address translator NAT as claimed in claim 1, wherein the method further comprises that the voice access device regularly sends a tunnel protocol handshake frame to the media gateway controller, In order to ensure that the NAT and firewall paths can be maintained; at the same time, the active state of the voice access device is maintained in the media gateway controller. 4. The method for voice signaling to penetrate firewalls and network address translators (NAT) according to any one of claims 1 to 3, wherein the general port opened by the media gateway controller is specifically a UDP port or TCP port.

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