KR20110129557A - Method for updating the nat port mapping table, and terminal and system using it - Google Patents

Abstract

PURPOSE: A method for updating a NAT(Network Address Translation) port mapping table, a terminal using the same, and a system thereof are provided to update the NAT port mapping table by using a service packet and an update packet. CONSTITUTION: A wireless communication unit(110) transmits a service packet for providing a specific service or update packet for updating an NAT port mapping table to an access point. A control unit(180) determines whether the service packet is transmitted at a second point within preset time from a first point to transmit the packet. The control unit transmits the update packet at the elapsed point of the preset time from the first or second point according to the transmission state of the service packet.

Description

METHODS FOR UPDATING THE NAT PORT MAPPING TABLE, AND TERMINAL AND SYSTEM USING IT}

The present invention relates to a method and system for updating and maintaining a NAT port mapping table.

Technological advances in computing devices and networking have facilitated access to a variety of information and services, making them accessible from virtually anywhere in the world. For example, home networks are becoming more and more common as they have more communication and / or computing devices to access the network.

Compared to registering individual IP addresses for each network device, a technique called Network Address Translation (NAT) allows multiple IP nodes behind a repeater or router to share a public IP address. .

To use a packet service on a client side that wants to use a particular packet service, there is a need to maintain or update a NAT port mapping table that maps a private IP on the client side and an external IP of a repeater or router.

On the terminal side to use packet service by using NAT, the internal IP of the terminal must be converted to the external IP to the server for the packet service through the NAT port mapping table. In that regard, the NAT port mapping table must be maintained or updated to provide packet services.

The present invention provides a system and a terminal for updating a NAT port mapping table using an update packet for periodically updating the NAT port mapping table and a service packet for providing a service.

In order to solve the above problems, the present invention relates to a network address translation (NAT) port mapping table updating system, in which at least one of a service packet for providing a specific service and an update packet for updating a NAT port mapping table is selected from an access point. And an access point configured to receive at least one of the service packet and the update packet from the terminal, and to update a NAT port mapping table using the received packet. Transmitting the update packet at an elapsed time of the prescribed time from any one of the first and second time points according to whether the service packet was transmitted at a second time point within a prescribed time from the first time point of transmission To provide a system.

In the system, when the terminal does not transmit the service packet at the second time point, the terminal transmits the update packet at the elapsed time point of the prescribed time from the first time point, and transmits the service packet at the second time point. When the update packet is transmitted from the second time point, the update packet is transmitted. If there is no transmission of the service packet, the update packet is periodically transmitted at the prescribed time interval.

In addition, in order to solve the above problems, the present invention provides a mobile communication module for transmitting at least one packet of a service packet for providing a specific service and an update packet for updating the NAT port mapping table, and transmitting the packet. It is determined whether the service packet has been transmitted at a second time point within a prescribed time from one first time point, and the update is made when the prescribed time elapses from any one of the first and second time points according to whether or not the service packet has been transmitted. It provides a mobile terminal, including a control unit for controlling to transmit a packet.

In addition, in order to solve the above problems, the present invention provides a terminal with at least one packet of a service packet for providing a specific service and an update packet for updating a network address translation (NAT) port mapping table. Determining whether the service packet was transmitted at a second time point within a prescribed time from the first time point at which the packet was transmitted, and as a result of the determination, not transmitting the service packet at the second time point. If not, the update packet is transmitted from the first time point at the elapse of the prescribed time, and when the service packet is transmitted at the second time point, the update packet at the elapsed time of the prescribed time from the second time point. It provides a NAT port mapping table update method comprising the step of transmitting a message.

According to the present invention, the NAT port mapping table can be updated by using not only an update packet for updating but also a service packet for providing a service.

Since the NAT port mapping table can be updated using service packets transmitted and received between the terminal and the AP, there is an effect of preventing power consumption and lifespan reduction due to periodic transmission of the update packet.

1 is a block diagram of a system in accordance with an embodiment of the present invention.
2 is a block diagram of a mobile terminal according to an embodiment of the present invention.
3 is a block diagram of an access point (AP) according to an embodiment of the present invention.
4 is a block diagram schematically illustrating a method of updating a NAT port mapping table according to an embodiment of the present invention.
5 is a diagram illustrating a concept of a method of updating a NAT port mapping table according to an embodiment of the present invention.
6 is a diagram illustrating a concept of a method of updating a NAT port mapping table according to another embodiment of the present invention.
7 is a flowchart schematically illustrating a method of updating a NAT port mapping table according to an embodiment of the present invention.

Hereinafter, a system and a mobile terminal related to the present invention will be described in more detail with reference to the accompanying drawings. The suffixes "module" and "unit" for various components used in the following description are given or used in consideration of ease of specification, and do not have distinct meanings or roles.

1 is a view schematically showing the structure of a system related to the present invention.

The mobile terminal 100 transmits at least one of an update packet or a service packet to the AP 200. When the AP 200 receives the update packet, the AP 200 uses the update packet to update the NAT port mapping table as described below. When the service packet is received, the AP 200 uses the corresponding service packet to map the NAT port. The table is updated or the service packet is converted through the NAT port mapping table and the packet is transmitted to the server 300. The server 300 may receive the packet and transmit the corresponding packet back to the AP 200. Through this, the terminal 100 can use a desired packet service.

Hereinafter, the structure of the terminal 100 and the AP 200 constituting the system will be described.

The terminal 100 described herein may include a mobile phone, a smart phone, a laptop computer, a digital broadcasting terminal, a personal digital assistant (PDA), a portable multimedia player (PMP), navigation, and the like. . However, it will be readily apparent to those skilled in the art that the configuration according to the embodiments described herein may also be applied to fixed terminals such as digital TVs, desktop computers, etc., except when applicable only to mobile terminals.

2 is a block diagram of a mobile terminal according to the present invention.

The mobile terminal 100 includes a wireless communication unit 110, an A / V input unit 120, a user input unit 130, a sensing unit 140, an output unit 150, a memory 160, and an interface. The unit 170, the controller 180, and the power supply unit 190 may be included. The components shown in FIG. 1 are not essential, so that a mobile terminal having more or fewer components may be implemented.

Hereinafter, the components will be described in order.

The wireless communication unit 110 may include one or more modules that enable wireless communication between the mobile terminal 100 and the wireless communication system or between the mobile terminal 100 and a network in which the mobile terminal 100 is located. For example, the wireless communication unit 110 may include a broadcast receiving module 111, a mobile communication module 112, a wireless Internet module 113, a short range communication module 114, and a location information module 115 .

The mobile communication module 112 transmits and receives a wireless signal with at least one of a base station, an external terminal, and a server on a mobile communication network. The wireless signal may include various types of data according to transmission and reception of a voice call signal, a video call call signal, or a text / multimedia message.

The wireless internet module 113 refers to a module for wireless internet access and may be embedded or external to the mobile terminal 100. Wireless Internet technologies may include Wireless LAN (Wi-Fi), Wireless Broadband (Wibro), World Interoperability for Microwave Access (Wimax), High Speed Downlink Packet Access (HSDPA), and the like.

The memory unit 160 may store a program for processing and controlling the controller 180, and temporarily stores input / output data (for example, a phone book, a message, an audio, a still image, a video, etc.). It can also perform a function for. The memory unit 160 may also store the frequency of use of each of the data (for example, each telephone number, each message, and frequency of use for each multimedia). In addition, the memory unit 160 may store data regarding vibration and sound of various patterns output when a touch input on the touch screen is performed.

The memory 160 may be a flash memory type, a hard disk type, a multimedia card micro type, a card type memory (for example, SD or XD memory), RAM (Random Access Memory, RAM), Static Random Access Memory (SRAM), Read-Only Memory (ROM), Electrically Erasable Programmable Read-Only Memory (EEPROM), Programmable Read-Only Memory (PROM), Magnetic Memory, Magnetic It may include a storage medium of at least one type of disk, optical disk. The mobile terminal 100 may operate in connection with a web storage that performs a storage function of the memory 160 on the Internet.

The interface unit 170 serves as a path with all external devices connected to the mobile terminal 100. The interface unit 170 receives data from an external device, receives power, transfers the power to each component inside the mobile terminal 100, or transmits data inside the mobile terminal 100 to an external device. For example, a wired / wireless headset port, an external charger port, a wired / wireless data port, a memory card port, a port for connecting a device having an identification module, an audio I / O port, A video input / output (I / O) port, an earphone port, and the like may be included in the interface unit 170.

The controller 180 typically controls the overall operation of the mobile terminal. For example, perform related control and processing for voice calls, data communications, video calls, and the like. The controller 180 may include a multimedia module 181 for playing multimedia. The multimedia module 181 may be implemented in the controller 180 or may be implemented separately from the controller 180.

The controller 180 may perform a pattern recognition process for recognizing a writing input or a drawing input performed on the touch screen as text and an image, respectively.

The power supply unit 190 receives an external power source and an internal power source under the control of the controller 180 to supply power for operation of each component.

Various embodiments described herein may be implemented in a recording medium readable by a computer or similar device using, for example, software, hardware or a combination thereof.

According to a hardware implementation, the embodiments described herein include application specific integrated circuits (ASICs), digital signal processors (DSPs), digital signal processing devices (DSPDs), programmable logic devices (PLDs), field programmable gate arrays (FPGAs), and the like. It may be implemented using at least one of processors, controllers, micro-controllers, microprocessors, and electrical units for performing other functions. The described embodiments may be implemented by the controller 180 itself.

According to the software implementation, embodiments such as the procedures and functions described herein may be implemented as separate software modules. Each of the software modules may perform one or more functions and operations described herein. Software code can be implemented in a software application written in a suitable programming language. The software code may be stored in the memory 160 and executed by the controller 180.

3 is a block diagram illustrating a structure of an access point (AP) according to the present invention.

In the present invention, the AP receives a packet from the mobile terminal and converts the packet using a NAT port mapping table to transmit the packet to the server.

The AP 200 includes a wireless communication module 210, a control module 220 and a memory 230.

The wireless communication module 210 receives a packet from the mobile terminal 100 and transmits the packet to the server. The control module 220 updates the NAT port mapping table using the received packet and controls to convert the packet using the corresponding NAT port mapping table. The memory 230 is responsible for storing a NAT port mapping table for a particular server.

The components of such an AP are exemplary and may include other components as necessary.

Hereinafter, a network address translation (NAT) and a NAT port mapping table will be described.

NAT is an Internet Engineering Task Force (IETF) standard used to enable multiple PCs or devices to share a single, globally routable IP address on a private network. Using NAT in a private network can cause network layer problems because all hosts outside the private network communicate through a single, shared IP address. NAT is not the same as a firewall or proxy server, but it also protects the network.

The terminal 100 related to NAT is generally assigned a private IP address through Dynamic Host Configuration Protocol (DHCP) or static configuration by an administrator. When the communication occurs outside the private network, the mobile terminal 100 performs the following tasks.

The upstream process of transmitting a packet from the terminal 100 to the server 300 is as follows.

When the service program attempts to communicate with the server 300, it opens a socket associated with the source IP, source port, destination IP address, destination port and network protocol. This process identifies the starting and ending points of communication. When the service program transmits the information using the socket, the personal IP address (source IP address) and port (source port) of the terminal 100 are inserted into the source field of the packet. Since these packets must reach the target point outside the private network, the terminal 100 forwards these packets to the designated default gateway. The default gateway is a NAT device, which corresponds to the AP 200 in the present invention.

The process of generating a packet transmitted from the NAT device, that is, the AP 200 at the terminal 100, in the NAT device is as follows.

The NAT device receives the transmitted packet and creates a port mapping using the destination IP address (server), destination port, NAT device's external IP address, external port, network protocol, and terminal's internal IP address and port. The NAT device manages this mapping table by storing these port mappings in a table. This mapping table is called the NAT port mapping table. The external IP address and port are the public IP address and port used for this data traffic instead of the internal client's IP address and port.

The NAT device then converts the packet by replacing the packet source fields in the terminal's private, internal IP address and port with the public, external IP address and port of the NAT device. Packets translated to external IP addresses and ports arrive at the server at that address.

4 is a diagram schematically illustrating a process of transmitting a packet through a NAT port mapping table.

Terminal 100 has its source IP address (10.0.0.2) and source port number (3123), destination IP address (143.23.0.4) and destination port number (80) of destination server 300 in the packet, gateway The address (10.0.0.1) of the AP 200 corresponding to the packet is inserted. The mobile terminal transmits a packet to the corresponding AP 200.

The AP 200, which is a NAT device, sets up a NAT port mapping table using the received packet. Set up the NAT port mapping table with the destination IP address, destination port, NAT device's external IP address, external port, and terminal's internal IP address and port.

The packet converted through the port mapping is transmitted to the server 300 by changing the external IP address (157.55.1.10) of the AP 200 whose source IP is a NAT device.

The downstream process of transmitting a packet from the server 300 side to the terminal 100 side is as follows.

Upon receiving the packet at server 300, server 300 may recognize that it is communicating with a single device having a routable IP address. The server 300 then sends a response packet to the external IP address and port of the NAT device using its IP address and port in the source field.

The packet received from the server 300 to the NAT device 200 is received by the NAT device 200 and compared with the NAT port mapping table. The source IP address and source port, destination port, and network protocol of the packet received at the NAT device 200 find a port mapping that matches the remote host IP address, remote port, external port, and network protocol of the port mapping. If you find a found port mapping, perform an inverse transformation. The AP 200, which is a NAT device, converts an external IP address and an external port of a packet target field into a private IP address and an internal port of the terminal 100.

The NAT device 200 transmits the converted packet to the terminal 100 side through the internal network. However, if the AP 200, which is a NAT device, does not find a matching port mapping, the packet to be transmitted is lost and the connection is lost.

Due to this risk, there is a need to maintain and update the port mapping table for proper port mapping between the mobile terminal 100 and the NAT device 200 in the case of a video call or a packet service such as a fixed mobile convergence (FMC) service. .

The advantage of the NAT system is that it can communicate over the Internet with a private IP address without any additional work on the terminal side. That is, the application service program does not need to call a separate API and the terminal 100 does not need to perform a separate configuration. In addition, the terminal 100 does not need to perform a separate configuration. In this case, NAT is transparent and smooth to both the terminal 100 and the server application service program.

If the mobile terminal 100 wants to receive a specific service such as a video call or an FMC call, a connection with a server for the service is required. As the information of the connected mobile terminal 100, when the corresponding server 300 of the network attempts to deliver the packet to the mobile terminal 100, information capable of correctly delivering the packet to the mobile terminal 100 is required. In this regard, the IP address inserted into the packet from the server 300 is accurately converted through the NAT port mapping table described above, and the packet is transmitted to the desired mobile terminal 100.

Therefore, when a specific packet service such as a video call or an FMC is desired, the NAT port mapping table must be updated and maintained at all times to provide the desired service.

Hereinafter, a method of updating a NAT port mapping table using an update packet or a service packet will be described.

First, the update packet and the service packet will be briefly described.

The update packet described herein refers to a packet transmitted from the mobile terminal 100 to the AP 200 in order to update the NAT port mapping table. In addition, the service packet refers to a packet for transmitting and receiving a packet service such as a video call or FMC. Therefore, transmitting the FMC call packet for the FMC call through the mobile terminal 100 means transmitting the service packet.

Both service packets and update packets are UDP packets. UDP packet consists of Source Port, Destination Port, Length, Checksum and Data. Therefore, there is no general configuration difference between the service packet and the update packet.

However, service packets and update packets are packets whose purpose is different. The service packet is for sending and receiving services, and the update packet is for updating the NAT port mapping table. Therefore, there is a difference in the data portion of the constituent portion of the UDP packet according to the difference in the purpose. That is, a service packet includes data for the service in the data portion. However, in the update packet, contents for updating are included in the data portion.

5 is a diagram illustrating a method of updating a NAT port mapping table using an update packet.

The update method of the NAT port mapping table shown in FIG. 5 is a method of transmitting an update packet from the mobile terminal 100 to the AP at regular intervals in order to maintain the NAT port mapping table.

As shown in the figure, an update packet is transmitted at a constant period (45 seconds in the figure). 45 seconds is exemplary and not limited. When the wireless communication unit 110 of the terminal 100 transmits an update packet, the wireless communication module 210 of the AP 200 receives it. The control module 220 of the AP 200 updates the NAT port mapping table using the received update packet.

The control module 220 of the AP 200 updates the NAT port mapping table using the source IP address and port of the update packet, the target IP address and port, and the internal IP address of the terminal 100. Through this, the NAT port mapping table stored in the AP 200 is updated and can access a related service.

Referring to the drawings, the first update packet 501 is transmitted through the wireless communication unit 110 of the terminal 100. The first update packet 501 is received via the wireless communication module 210 of the AP 200 and the control module 220 of the AP 200 uses the first update packet 501 to generate a NAT port mapping table. Update After the 45 second update period, the controller 180 of the terminal 100 controls the wireless communication unit 110 to transmit the second update packet 503. The transmitted second update packet 503 is received by the AP 200, and the control module 220 of the AP 200 re-updates the NAT port mapping table using the second update packet 503. Thereafter, after transmitting the second update packet 503, the third update packet 504 is transmitted 45 seconds later, and the NAT port mapping table is updated again. This process is repeated. If this process is stopped, the service is disconnected.

In the figure, an FMC call packet 502 which is a service packet is transmitted between the first update packet 501 and the second update packet 503. However, here the FMC call packet 502 does not update the NAT port mapping table. The FMC call packet 502 is translated through the NAT port mapping table and sent to the server 300.

Through this process, the update packet is periodically transmitted and the NAT port mapping table is updated using the update packet.

6 is a diagram illustrating a method of updating a NAT port mapping table using an update packet and a service packet.

The update method of the NAT port mapping table shown in FIG. 6 uses a service packet as well as an update packet to maintain a NAT port mapping table.

As described with reference to FIG. 5, the wireless communication unit 110 of the terminal 100 transmits an update packet and a service packet. The transmitted packets are received via the wireless communication module 210 of the AP 200. The control module 220 of the AP 200 updates the NAT port mapping table using the received packets. That is, the control module 220 of the AP 200 updates the NAT port mapping table using the source IP address and port of the packet, the destination IP address and port, and the internal IP address of the terminal 100. Through this, the NAT port mapping table stored in the AP 200 is updated and can access a related service.

Referring to the drawings, the wireless communication unit 110 of the terminal 100 transmits the first update packet 610. The transmitted first update packet 610 is received via the wireless communication module 210 of the AP 200. The control module 220 of the AP 200 updates or sets the NAT port mapping table using the received first update packet 610. Although only the NAT port mapping table is updated in the figure, the process is the same when the NAT port mapping table is updated or configured by using an update packet or a service packet received by the AP 200.

After the NAT port mapping table is updated by the first update packet 610 and before a certain period of time (45 seconds in the drawing) of the update packet is transmitted, the service packet 612 is connected to the wireless communication unit of the terminal 100. 110).

In the present embodiment, the NAT port mapping table may be updated not only by the update packet but also by the service packet. Therefore, the FMC call packet 612, which is a service packet, is transmitted from the terminal 100 and received by the AP 200. The control module 220 of the AP 200 updates the NAT port mapping table using the received FMC call packet 612.

When the NAT port mapping table is updated by the service packet, the second update packet 614 which is to be transmitted after the period of the update packet has elapsed is not transmitted. Therefore, the controller 180 of the terminal 100 determines whether to transmit the update packet or the service packet, and does not transmit the update packet when the service packet is transmitted.

The controller 180 of the terminal 100 calculates the transmission time of the next update packet not from the transmission time of the immediately previous update packet, but from the time when the NAT port mapping table is updated. In other words, if there is no service packet transmission after the update packet is transmitted, the next update packet is transmitted when the update cycle has elapsed therefrom. When the period elapses, the next update packet is transmitted.

Referring to the figure, when the NAT port mapping table is updated through the FMC call packet 612, which is a service packet, the update packet 614 is not transmitted after the update period of the first update packet 610. Instead, the FMC call packet 612 is transmitted to transmit the second update packet 616 45 seconds after the update period from the time when the NAT port mapping table is updated. The second update packet 616 is received by the wireless communication module 210 of the AP 200 and the control module 220 of the AP 200 updates the received second update packet 616.

This process is repeated and in the case where the FMC call packet 618 is transmitted after the second update packet 616 is transmitted, the update period is counted again from the time when the FMC call packet 618 is transmitted.

Through this process, the NAT port mapping table is updated and maintained. Accordingly, the terminal 100 can be connected to the desired service program.

For convenience of description, the service is described as an FMC call, but all the services based on the packet service can be applied to the present invention. For example, the video call service, which is a packet service, may also update the NAT port mapping table through the video call packet, and accordingly, the present invention may be applied.

7 is a flowchart illustrating a method of updating a NAT port mapping table according to an embodiment of the present invention.

The mobile terminal 100 transmits a service packet or an update packet at the first time point in step S710.

The AP 200 updates the NAT port mapping table using the packets (S720).

The controller 180 of the mobile terminal 100 determines whether the service packet is transmitted within a prescribed time which is an update period after transmitting the packet at the first time point (S730).

If it is determined that the service packet has been transmitted, the mobile terminal 100 transmits the service packet at the second time point. The control module 220 of the AP 200 updates the NAT port mapping table by using the corresponding service packet. In addition, the update packet is transmitted after the elapse of the prescribed time from the second time point at which the service packet is transmitted (S740). The control module 220 of the AP 200 updates the NAT port mapping table using the corresponding packet (S760).

If it is determined that the service packet has not been transmitted, the wireless communication unit 110 of the mobile terminal 100 transmits an update packet after the prescribed time elapses from the first time point (S750). The wireless communication module 210 of the AP 200 receives the update packet and the control module 220 of the AP 200 updates the NAT port mapping table using the update packet (S760).

The above steps are repeated and stop sending packets if you want to terminate the service.

In addition, according to an embodiment of the present invention, the above-described updating method of the NAT port mapping table can be implemented as code that can be read by a processor in a medium in which a program is recorded. Examples of processor-readable media include ROM, RAM, CD-ROM, magnetic tape, floppy disk, optical data storage, and the like, and may be implemented in the form of a carrier wave (for example, transmission over the Internet). Include.

The method of updating the NAT port mapping table described above and the terminal and system using the same are not limited to the configuration and method of the above-described embodiments, but the embodiments may be modified in various ways. All or some of these may optionally be combined.

100 terminal 110 wireless communication unit
180 control unit 200 AP
210 Wireless Communication Module 220 Control Module
300 servers

Claims (12)

In the network address translation (NAT) port mapping update system,
A terminal for transmitting at least one packet of a service packet for providing a specific service and an update packet for updating a NAT port mapping table; And
An access point for receiving at least one of the service packet and the update packet from the terminal and updating a NAT port mapping table using the received packet;
The terminal, at a second time point within a prescribed time from the first time point of transmitting the packet, elapses time point of the prescribed time from any one of the first and second time points according to whether the service packet is transmitted. Send the update packet to the system. The method of claim 1,
The terminal,
If the service packet is not transmitted at the second time point, the update packet is transmitted from the first time point when the prescribed time elapses,
And when the service packet is transmitted at the second time point, the update packet is transmitted from the second time point when the prescribed time elapses. The method of claim 1,
The terminal,
And if there is no transmission of the service packet, periodically sending the update packet at the prescribed time interval. The method of claim 1,
The specific service includes at least one of a video call and a Fixed Mobile Convergence (FMC) service. A wireless communication unit which transmits at least one packet of a service packet for providing a specific service and an update packet for updating a NAT port mapping table; And
It is determined whether the service packet has been transmitted at a second time point within a prescribed time from the first time point of transmitting the packet, and depending on whether or not the packet is transmitted, from the time point of any one of the first and second time points, And a control unit controlling to transmit the update packet at an elapsed time point. The method of claim 5, wherein
At least one of the service packet and the update packet is transmitted to the access point and used for updating the NAT port mapping table. The method of claim 5, wherein
The control unit,
If the service packet is not transmitted at the second time point, control the wireless communication unit to transmit the update packet from the first time point when the prescribed time elapses,
And when the service packet is transmitted at the second time point, controlling the wireless communication unit to transmit the update packet at a time point when the prescribed time elapses from the second time point. The method of claim 5, wherein
The control unit,
And if there is no transmission of the service packet, controlling the wireless communication unit to periodically transmit the update packet at the prescribed time interval. The specific service includes at least one of a video call and a fixed mobile convergence (FMC) service. Transmitting, by the terminal, at least one packet of a service packet for providing a specific service and an update packet for updating a network address translation (NAT) port mapping table to an access point;
Determining whether the service packet was transmitted at a second time point within a prescribed time from the first time point at which the packet was transmitted; And
If the service packet is not transmitted at the second time point as a result of the determination, the update packet is transmitted from the first time point when the prescribed time has elapsed, and the service packet is transmitted at the second time point. And transmitting the update packet from a time point 2 to the elapsed time of the prescribed time. The method of claim 10,
And if there is no transmission of the service packet, periodically transmitting the update packet at the prescribed time interval. The method of claim 10,
At least one of the service packet and the update packet is transmitted to the access point and used for updating the NAT port mapping table.

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