KR100612007B1 - Interconnection method and apparatus between IPv4 network and IPv6 network - Google Patents

Abstract

The present invention relates to IPv6 (Internet Protocol version 6), and more particularly, to interworking between an IPv6 network and an IPv4 network. An interworking system between an IPv6 network and an IPv4 network of the present invention is an interworking system between an IPv6 network and an IPv4 network including a NAT-PT (NAT-PT) performing apparatus for performing packet forwarding between an IPv6 node and an IPv4 node. A first NAT-PT performing apparatus for performing IP packet forwarding; And a second NAT-PT performing apparatus for performing the IP packet forwarding when the processing capacity of the first NAT-PT performing apparatus is exceeded. The first NAT-PT performing apparatus and the second NAT-PT performing apparatus are provided. The performing apparatus is characterized by sharing each packet processing state information using a predetermined message. The IPv4-IPv6 interworking method of the present invention has an effect of improving the packet processing speed and performance than using a conventional NAT-PT performing apparatus by properly arranging the NAT-PT performing apparatus according to the size of the network.

Description

Interconnection method and apparatus between IPv4 network and IPv6 network

1 is a diagram illustrating interworking between an IPv6 network and an IPv4 network using a NAT-PT performing apparatus.

2 is a diagram illustrating conversion between an IPv4 packet header and an IPv6 packet header performed by SIIT.

3 is a diagram illustrating a process of establishing a session from an IPv6 node to an IPv4 node using NAT-PT as an example.

4 illustrates an ICMPv6 redirect message format.

5 is a diagram illustrating interworking between an IPv6 network and an IPv4 network using a plurality of NAT-PT execution apparatuses.

6 is a detailed block diagram of a NAT-PT performing apparatus.

7 is a flowchart of a method for interworking between an IPv6 network and an IPv4 network using a plurality of NAT-PT devices of the present invention.

8 is a flowchart of a method for interworking between an IPv6 network and an IPv4 network using the DNS-ALG of the present invention.

9 is a format of Reply data.

10 is a block diagram of a DNS-ALG function unit included in a NAT-PT performing apparatus when using the DNS-ALG function.

The present invention relates to IPv6 (Internet Protocol version 6), and more particularly, to interworking between an IPv6 network and an IPv4 network.

As network devices using IPv6 increase in recent years, the IPv6 network has spread significantly. However, since most network devices are mostly used in existing IPv4 networks, interworking between IPv6 networks and IPv4 networks is required, and for this purpose, IP address interchange is required.

That is, in order for the nodes connected to the IPv6 network and the nodes connected to the IPv4 network to communicate with each other, an address translator for translating an IPv6 address and an IPv4 address is required. Among the methods of translating IPv6 and IPv4 addresses, Network Address Translation-Protocol Translation (NAT-PT) is an address translation and protocol translation technique used in IPv6-IPv4 networks.
NAT-PT is a standard established by the Internet Engineering Task Force (IETF), the Internet International Standardization Organization, as RFC 2766, and describes IPv6-IPv4 translation. With NAT-PT, hosts or applications connected to an IPv6 network can also communicate with hosts or applications connected to an IPv4 network. Of course, each of these hosts has only IPv6 and IPv4 stacks, and the device performing NAT-PT is located at the boundary between IPv6 and IPv4 networks. Devices that perform NAT-PT are typically located where the perimeter router is located and have an IPv4 / IPv6 dual stack. In addition, the device performing NAT-PT has an IPv4 address pool that collects IPv4 addresses that are dynamically allocated when hosts connected to IPv6 networks want to communicate with hosts connected to IPv4 networks. These addresses are, of course, official IPv4 addresses.
NAT-PT performs two functions, as its name suggests. The first is the NAT (Network Address Translation) function, which performs address translation by placing an IPv4 address pool for dynamically assigning an IPv4 address to an IPv6 node every time the session is initiated and located at a boundary router between two networks. In other words, it acts as an address mapper and changes the address in the IPv4 and IPv6 packet headers.
The second is Protocol Translation (PT), which performs address translation based on the RFC 2765 standard document Stateless IP / ICMP Translation Algorithm (SIIT) that defines the translation function at the host. In addition, in order to dynamically allocate and convert an address, additional requirements are generated by applications including IP address or port information in a payload region, and an application level gateway (ALG) must be used to support this. Typical examples include DNS-ALG and FTP-ALG. DNS ALG performs AAAA and A format conversion and exchanges address information between DNSv4 and DNSv6. Such ALGs are distinct from application proxies and, unlike application proxies, do not require additional proprietary protocols.

1 is a diagram illustrating interworking between an IPv6 network and an IPv4 network using a NAT-PT performing apparatus.

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NAT-PT performing apparatus 110 converts an IPv4 address into an IPv6 address, or vice versa. The NAT-PT performing apparatus 110 also includes a stateless IP / ICMP translation (SIIT) performing unit that provides a function of converting a 32-bit IPv4 header and a 128-bit IPv6 header.

2 is a diagram illustrating conversion between an IPv4 packet header and an IPv6 packet header performed by SIIT.

The ToS field 201 of the IPv4 packet header 200 corresponds to the Class field 251 of the IPv6 packet header 250, and a value obtained by subtracting the header length from the Total Length 202 of the IPv4 packet header 200 is an IPv6 packet. It is mapped to the Payload Length field 251 of the header 250. In addition, the TTL field 203 of the IPv4 packet header 200 corresponds to the Hop Limit field 253 of the IPv6 packet header 250, and the Protocol 204 is mapped to the Next Header 254. Other fields of the IPv6 packet header 250 that are not defined in the IPv4 packet header 200 are calculated and inserted by themselves.

The DNSv6 server 120 supports a AAAA type query for searching an IPv6 address and is a domain name server that provides an IP address for a host name of an IPv6 network.

In the NAT-PT specification defined in RFC 2766, an IPv4 pool that stores IPv4 addresses mapped to IPv6 addresses when IPv6 to IPv4 addresses are translated, and an IPv4 node to find IPv6 nodes to which packets are sent. Is a DNS static mapping section that sends a query to the DNSv6 server to retrieve the address of an IPv6 node and performs the mapping from an IPv4 address to an IPv6 address, the upper prefix used when the IPv4 address is converted to a 128-bit IPv6 address. A mapping table, which is a table that stores a 96-bit dummy prefix that is a prefix and relationship information between the converted IPv4 address and the IPv6 address, is defined.

In order for one node 130a of IPv6 to be connected to one node 140a of the IPv4 network, the following process is performed.

Since the address of the IPv4 node 140a needs to be found, the DNSv6 server 120 performs an A-type DNS query. However, the DNSv6 server 120 cannot find the address of the IPv4 node 140a. Therefore, the packet is sent to the DNSv4 server 150 by looking at the address of the DNSv4 server 150 stored in the secondary DNSv6 server. The DNSv4 server 150 transmits the address of the IPv4 node 140a to the NAT-PT performing apparatus 110. The NAT-PT performing apparatus 110 attaches a 96-bit prefix to the address of the IPv4 node 140a included in the data packet, generates a 128-bit IPv6 address, and transmits the data packet to the IPv6 node 140a.

After obtaining the IPv4 address in this manner, the IPv6 node forwards the packet to be transmitted to the NAT-PT performing unit 110. The NAT-PT performing unit 110 receiving the packet converts an IPv6 address into an IPv4 address. In other words, the source address gets the IPv4 address mapped from the IPv6 address from the IPv4 address pool, and the destination address is the IPv6 address with 96-bit dummy prefix to the IPv4 address to be connected. Use the lower 32 bits.

The data packet is sent to the IPv4 node with the source address and the destination address. On the contrary, in order to transmit data from the node connected to the IPv4 network to the node connected to the IPv6 network, the mapping table in the NAT-PT performing unit 110 is generated and the address is translated. That is, the mapping table is a table in which an IPv4 address and an IPv6 address are corresponded. NAT-PT performing unit 110 transmits the packet to the final IPv4 destination. On the contrary, in order to transmit data from the node connected to the IPv4 network to the node connected to the IPv6 network, the mapping table in the NAT-PT performing unit 110 is generated and the address is translated.

3 is a diagram illustrating a process of establishing a session from an IPv6 node to an IPv4 node using NAT-PT as an example.

If the source address of the IPv6 host 310 is FEDC: BA98 :: 7654: 3210, and the destination address is 132.146.243.30, the NAT-PT device 320 uses the address pool 330 to source FEDC: BA98 :: The IPv4 address corresponding to 7654: 3210 is assigned. If the assigned IPv4 address is 120.130.26.10, the source address is set to 120.130.26.10 from now on to the destination IPv4 host 340.

However, when using such a NAT-PT technology, all packets must be processed by the NAT-PT device 320. Therefore, when there are more nodes connected to the IPv6 network, the amount of data to be processed by the NAT-PT device 320 increases rapidly. Therefore, there is a problem that it is difficult to use in a large network.

In order to solve this problem, a subnet may be formed by grouping nodes connected to an IPv6 network and an IPv4 network, or a network may be configured to include a plurality of NAT-PT devices, but information between subnets or between a plurality of NAT-PT devices may be used. There is a problem that can not be shared.

The technical problem to be achieved by the present invention is to provide a plurality of NAT-PT devices, and share information related to data processing between the plurality of NAT-PTs using a redirect message defined in the NDP (Neighbor Discovery Protocol). The present invention provides an IPv6-IPv4 network interworking method and interworking device.

Another technical problem to be solved by the present invention is to sequentially allocate a plurality of prefixes used when converting between IPv4 and IPv6 addresses using the DNS-ALG function provided by a NAT-PT device, or to perform the least load of NAT-PT. An object of the present invention is to provide a method for interworking with an IPv6-IPv4 network that allocates a prefix of a device.

According to an aspect of the present invention, in an interworking system between an IPv6 network and an IPv4 network including an IP packet forwarding apparatus for performing IP packet forwarding between an IPv6 node and an IPv4 node, the first IP packet forwarding performing IP packet forwarding is performed. Device; And a second IP packet forwarding device that performs the IP packet forwarding when the processing capacity of the first IP packet forwarding device is exceeded, wherein the first IP packet forwarding device and the second IP packet forwarding device include: It is achieved by an interworking system between an IPv6 network and an IPv4 network, wherein processing status information of the IP packet is shared with each other using a predetermined message.
The first IP packet forwarding device and the second IP packet forwarding device preferably forward packets using NAT-PT (Network Address Translation-Protocol Translation).
In addition, according to the present invention, in the interworking system between the IPv6 network and the IPv4 network having a network address translation-protocol translation (NAT-PT) performing apparatus for performing packet forwarding between the IPv6 node and IPv4 node, IP A first NAT-PT performing apparatus for performing packet forwarding; And a second NAT-PT performing apparatus for performing the IP packet forwarding when the processing capacity of the first NAT-PT performing apparatus is exceeded. The first NAT-PT performing apparatus and the second NAT-PT performing apparatus are provided. The performing apparatus is also achieved by an interworking system between an IPv6 network and an IPv4 network, wherein each packet processing state information is shared using a predetermined message.
The predetermined message is preferably an ICMPv6 redirect message defined by the NDP (Neighbor Discovery Protocol).
On the other hand, according to another field of the present invention, the technical problem in the NAT-PT performing apparatus, receiving the IPv6 packet, and can process the received IPv6 packet according to the current packet processing state of the NAT-PT performing apparatus. Determination unit for determining whether there is; An IPv4 address pool storing an IPv4 address that can be used by mapping an address of an IPv6 node that has transmitted the IPv6 packet to an IPv4 address; A mapping table generation and storage unit for generating and storing a table for mapping an IPv4 address corresponding to the address of the IPv6 node; And an IP header converting unit for converting the IPv6 packet header into the IPv4 packet header.
On the other hand, according to another field of the present invention, the technical problem is an IPv6 network to the IPv6-IPv4 interworking system having a NAT-PT (Network Address Translation-Protocol Translation) performing apparatus for performing packet transfer between the IPv6 node and IPv4 node In the interworking method between the network and the IPv4 network, a plurality of NAT-PT performing apparatuses exist, and each packet processing state information is shared by using a predetermined message between the NAT-PT performing apparatuses. It is also achieved by the interworking method between the network and the IPv4 network.

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The predetermined message is preferably an ICMPv6 redirect message defined by the NDP (Neighbor Discovery Protocol).
In the NAT-PT performing method performed in a NAT-PT performing apparatus, the technical problem may include (a) receiving an IPv6 packet and processing the received IPv6 packet according to a current packet processing state of the NAT-PT performing apparatus. Determining whether it is possible; (b) mapping the address of the IPv6 node that has transmitted the IPv6 packet to the IPv4 address from the IPv4 address pool storing the available IPv4 address, if the determined result can process the received IPv6 packet; And (c) converting the header of the received IPv6 packet into an IPv4 packet header.
The technical problem is a method for interworking between a network composed of the IPv6 node and a network composed of the IPv4 node in a network having at least one device for performing IP packet forwarding between an IPv6 node and an IPv4 node. Receiving a DNS message looking for an IPv4 address for the server and delivering it to a DNSv4 server to receive an IPv4 address for the destination domain name; (b) converting the received IPv4 address into an IPv6 address by attaching a predetermined prefix to the received IPv4 address; And (c) it is also achieved by the interworking method between the IPv6 network and IPv4 network comprising the step of transmitting the converted IPv6 address information to the IPv6 node.

On the other hand, according to another field of the present invention, the technical problem is to link between the network consisting of the IPv6 node and the network consisting of the IPv4 node of the network having one or more devices for performing IP packet forwarding between IPv6 node and IPv4 node. An interworking apparatus comprising: a DNS message receiving unit for receiving a DNS message for finding an IPv4 address for a destination domain name; An IPv4 address receiving unit for transmitting the received DNS message to a DNSv4 server and receiving an IPv4 address for the destination domain name; An address conversion unit converting the received IPv4 address into an IPv6 address by attaching a predetermined prefix to the received IPv4 address; And a transmission unit for transmitting the converted IPv6 address information to the IPv6 node.

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In order to achieve the above object, the present invention provides a computer-readable recording medium recording a program for executing the method on a computer.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

4 illustrates an ICMPv6 redirect message format.

Internet Control Message Protocol (ICMP) is defined in RFC 792 as a protocol for controlling messages and reporting errors between a host server and an Internet gateway. ICMP uses IP datagrams, but the messages are processed by TCP / IP software and are not directly visible to the application user. As an example, the ping command uses ICMP to test the Internet connection. ICMPv6 is the ICMP used for IPv6.

The ICMPv6 redirect message includes a type field 410, code information 420, checksum 430, reserved 440, target address 450, It consists of a destination address 460 and an option field 470.

In the ICMP message standard, a value of 137 is stored in the type field 410, and 0 is stored in the code information 420. These values are set in the ICMP message specification. The checksum 430 is for checking for errors and is a checksum of ICMPv6. The target address 450 redirects the packet to the neighboring NAT-PT performer when the current NAT-PT performer has too many packets to process and cannot process all of them. The address of is stored. The destination address 460 stores the address of the current NAT-PT performing apparatus.

A flag 441 may be provided in the reserved field 440 to store information indicating that there are too many packets to be processed by the current NAT-PT so that another neighboring NAT-PT should process the packet.

5 is a diagram illustrating interworking between an IPv6 network and an IPv4 network using a plurality of NAT-PT execution apparatuses.

In the present invention, a plurality of NAT-PT execution apparatuses 510a, 510b, and 510c are provided, and a plurality of NAT-PT execution apparatuses use a redirect message defined in NDP to process the amount of packets processed by a specific NAT-PT execution apparatus. If so, then it can be processed by other NAT-PT performers.

Each NAT-PT implementer can know the current packet processing status by using the mapping table that stores the translated IPv4-IPv6 address. In other words, the mapping table is dynamically created and deleted over time. When the mapping table grows to a certain extent, it can be seen that a large amount of packets are currently being processed. If the size of the mapping table is determined, the current packet processing status of the NAT-PT performing apparatus can be known by observing the utilization rate of the mapping table indicating how much the mapping table is currently used. You can also see the current packet processing status by observing how many IPv4 addresses are allocated and used in the IPv4 pool.

At this time, the efficiency of each NAT-PT performing apparatus is increased by using a threshold that means an appropriate amount of packets that each NAT-PT performing apparatus can process. Each threshold can be set by the user. For example, if you set the threshold to 80% on each NAT-PT performer, and the 80% of the NAT-PT performer's ability to process the packet reaches the other NAT-PT performer via a redirect message. Send it for processing.

Now, assuming that the threshold is set to 80%, the process of connecting the IPv6 node to the IPv4 node will be described. First, the IPv6 node sends a packet to the NAT-PT performer. The NAT-PT performing apparatus that receives the packet converts the received packet into an IPv4 header and transmits the received packet to the IPv4 node when its packet processing status is 80% or less. If the NAT-PT performer receiving the packet has a packet processing status of 80% or more, the ICMPv6 redirect message is used to send the packet to another NAT-PT performer.

That is, if the address of the NAT-PT performer in the neighbor is loaded in the target address area of the ICMPv6 redirect message and the flag bit is set, the IPv6 node receiving the redirect message sends a new packet. The packet is sent to the NAT-PT performing apparatus having the target address, and then the packet is distributed to the IPv4 node after the session establishment process described with reference to FIG. 3.

6 is a detailed block diagram of a NAT-PT performing apparatus.

The NAT-PT performing apparatus 600 includes a determination unit 610, an IPv4 address pool 620, a mapping table generation and storage unit 630, and an IP header conversion unit 640.

The determination unit 610 receives the IPv6 packet, and determines whether the node can process the IPv6 packet according to the current packet processing state of the NAT-PT performing apparatus 600. As described above, the current packet processing status of the NAT-PT performing apparatus 600 can be known by observing the size or usage rate of the mapping table or the usage status of the IPv4 address pool. Receiving a packet processing state above a predetermined threshold means that the NAT-PT performer 600 is difficult to process IPv6 packets, so from now on, send the packet to another neighboring NAT-PT performer. Must issue the command as an IPv6 node, using a redirect message.

This may be indicated by placing a flag bit in the reserved field of the redirect message or may not use the flag bit. In the target address field of the ICMPv6 redirect message, the address information of the neighboring NAT-PT performing device is displayed.

The IPv4 address pool 620 stores IPv4 addresses that can be used by mapping IPv6 addresses to IPv4 addresses. The mapping table generation and storage unit 630 generates a table for mapping an IPv4 address corresponding to the address of the IPv6 node.

The IP header converter 640 converts the IPv4 packet header into an IPv6 packet header. The transformation can use SIIT technology. The conversion of the header is as described with reference to FIG.

7 is a flowchart of a method for interworking between an IPv6 network and an IPv4 network using a plurality of NAT-PT devices of the present invention.

First, an IPv6 packet is received (S710), and a current packet processing state of the NAT-PT performing apparatus is received (S720). If the current packet processing state is equal to or greater than a predetermined threshold set in consideration of the processing capacity that can be processed by the NAT-PT performing apparatus, the received IPv6 packet cannot be processed, and thus, the IPv6 packet can no longer be processed. The information is transmitted to the IPv6 node (S740). The processing status of the current packet can be known by observing the size or usage rate of the mapping table or the usage status of the IPv4 address pool as described above. Information that it can no longer handle IPv6 packets and other NAT-PT address information is forwarded to the IPv6 node using ICMPv6 redirect messages.

If it is less than the predetermined threshold, the IPv4 address mapped to the IPv6 node address is read from the IPv4 address pool (S750), the header of the received IPv6 packet is converted into an IPv4 header (S760), and the packet received from the IPv6 node is IPv4. Send to the node (S770).

8 is a flowchart of a method for interworking between an IPv6 network and an IPv4 network using the DNS-ALG of the present invention.

The DNS-ALG Execution Unit contains all prefix information of the network. That is, it has all the prefix information assigned to each NAT-PT execution device. This prefix information is used to translate an IPv4 address into an IPv6 address. The DNS-ALG Execution Unit resides in the NAT-PT Execution Unit.

First, the DNS-ALG execution unit receives a DNS message that finds an IPv4 address for a destination domain name (S810). Then, the received DNS message is delivered to the DNSv4 server to receive an IPv4 address for the destination domain name (S820). The DNS message contains the address of the IPv4 node and the address of the DNSv4 server, and the DNSv4 server address must be translated into an IPv4 address. That is, when an IPv6 node wants to access an IPv4 node, the IPv6 node finds address information of the IPv4 node through a DNSv4 server.

Subsequently, a predetermined prefix is attached to the received IPv4 address and converted into an IPv6 address (S830). Here, the predetermined prefix is one of the prefixes assigned to NAT-PT performing apparatuses performing IP packet forwarding sequentially. Alternatively, the load information of the NAT-PT devices may be received to determine which NAT-PT is currently the most relaxed, and may be translated into an IPv6 address with the prefix assigned to the NAT-PT device. The load information is received using the Code field of the ICMPv6 redirect message described with reference to FIG. 4 and the Qtype field of the reply data message as described with reference to FIG. 9 described later. Code value and Qtype value are not specified. Finally, the converted IPv6 address information is transmitted to the IPv6 node (S840).

9 is a format of Reply data.

The reply data includes a Qtype field 910, an unused field 920, an L field 930, a T field 940, and a P field 950. If the L field 930 is set to 1, it means that a link local address is required. If the T field 940 is set to 1, it means that a threshold is required. If set to 1, it means that prefix information is requested.

10 is a block diagram of a DNS-ALG function unit included in a NAT-PT performing apparatus when using the DNS-ALG function.

The DNS-ALG function unit includes a DNS message receiver 1010, an IPv4 address receiver 1020, an address translator 1030, and a transmitter 1040.

The DNS message receiving unit 1010 receives a DNS message that finds an IPv4 address for a destination domain name. The IPv4 address receiving unit 1020 transmits the received DNS message to the DNSv4 server and receives the IPv4 address for the destination domain name. The address conversion unit 1030 converts the received IPv4 address into an IPv6 address by attaching a predetermined prefix to the received IPv4 address. The transmitter 1040 transmits the converted IPv6 address information to the IPv6 node.

The prefix allocated by the address translator 1030 may be a sequence of prefixes allocated to a plurality of NAT-PT performing apparatuses, and load information of the NAT-PT performing apparatus is described with reference to FIGS. 8 and 9. Similarly, prefixes received using ICMPv6 redirect messages and reply messages can be used to assign the least loaded NAT-PT execution device.

The invention can also be embodied as computer readable code on a computer readable recording medium. The computer-readable recording medium includes all kinds of recording devices in which data that can be read by a computer system is stored. Examples of computer-readable recording media include ROM, RAM, CD-ROM, magnetic tape, floppy disk, optical data storage, and the like, and may also be implemented in the form of a carrier wave (for example, transmission over the Internet). Include. The computer readable recording medium can also be distributed over network coupled computer systems so that the computer readable code is stored and executed in a distributed fashion.

So far I looked at the center of the preferred embodiment for the present invention. Those skilled in the art will appreciate that the present invention can be implemented in a modified form without departing from the essential features of the present invention. Therefore, the disclosed embodiments should be considered in descriptive sense only and not for purposes of limitation. The scope of the present invention is shown in the claims rather than the foregoing description, and all differences within the scope will be construed as being included in the present invention.

As described above, in the interworking method between the IPv6 network and the IPv4 network of the present invention, by appropriately disposing a NAT-PT performing apparatus according to the size of the network, the packet processing speed and performance are higher than those of the conventional single NAT-PT performing apparatus. There is an improved effect. Since the threshold value is set, the overload of the NAT-PT performing apparatus can be prevented. In addition, since it uses the NMP ICMPv6 redirect message used in the existing router, it is easy to implement a distributed processing environment.

In addition, by appropriately selecting one of the prefixes assigned to the plurality of NAT-PT executing apparatuses using the DNS-ALG function and converting it into an IPv6 packet, the load between NAT-PT executing apparatuses is equalized.

Claims (35)

delete delete In an interworking system between an IPv6 network and an IPv4 network having a NAT-PT (Network Address Translation-Protocol Translation) performing apparatus for performing packet forwarding between an IPv6 node and an IPv4 node, A first NAT-PT performing apparatus for performing IP packet forwarding; And And a second NAT-PT executing apparatus for performing the IP packet forwarding when the processing capacity of the first NAT-PT executing apparatus is exceeded. The first NAT-PT executing apparatus and the second NAT-PT executing apparatus share each packet processing state information using an ICMPv6 redirect message defined by a neighbor discovery protocol (NDP). Interworking system between IPv4 networks. delete The method of claim 3, wherein the ICMPv6 redirect message is A flag bit indicating a packet processing state of the first NAT-PT performing apparatus; And And a target address field for storing an address of the second NAT-PT performing apparatus neighboring the first NAT-PT executing apparatus. The packet processing state of claim 3, wherein the first NAT-PT performing apparatus or the second NAT-PT executing apparatus is The current packet processing state obtained by the size of the IPv6-IPv4 address translation mapping table included in each NAT-PT performing apparatus or the degree of use of the mapping table is a predetermined value indicating the packet processing capacity that NAT-PT can process. An interworking system between an IPv6 network and an IPv4 network, characterized by being above a threshold. The packet processing state of claim 3, wherein the first NAT-PT performing apparatus or the second NAT-PT executing apparatus is Indicates whether the current packet processing state obtained by the usage state of the IPv4 address pool provided in each NAT-PT performing apparatus is greater than or equal to a predetermined threshold indicating the packet processing capacity that NAT-PT can process. An interworking system between an IPv6 network and an IPv4 network. In the apparatus for performing NAT-PT, Receives an IPv6 packet, determines whether the received IPv6 packet can be processed according to a current packet processing state, and if it is determined that the IPv6 packet cannot be processed, the IPv6 packet through a predetermined message. A determination unit for instructing an IPv6 node that transmits the IPv6 packet to a NAT-PT performing apparatus other than the NAT-PT performing apparatus; An IPv4 address pool storing an IPv4 address that can be used by mapping an address of an IPv6 node that has transmitted the IPv6 packet to an IPv4 address; A mapping table generation and storage unit for generating and storing a table for mapping an IPv4 address corresponding to the address of the IPv6 node; And NAT-PT performing apparatus for converting an IPv6 packet header to an IPv4 packet header. The method of claim 8, wherein the determination unit The reception state of the current packet of the NAT-PT performing apparatus is determined depending on whether the value obtained by the size of the mapping table or the degree of use of the mapping table or the state of use of the IPv4 address pool is equal to or greater than a predetermined threshold value. NAT-PT performing apparatus for determining whether one of the IPv6 packets can be processed. delete The method of claim 8, And the predetermined message is a redirect message of ICMPv6. The method of claim 11, wherein the redirect message is A flag bit indicating a packet processing state of the NAT-PT performing apparatus; And NAT-PT performing apparatus comprising a target address field for storing the address of another NAT-PT performing apparatus adjacent to the NAT-PT performing apparatus. The method of claim 8, wherein the IP header conversion unit NAT-PT performing apparatus for converting an IP header using a stateless IP / ICMP Translation Algorithm (SIIT). In an interworking method between an IPv6 network and an IPv4 network in an IPv6-IPv4 interworking system having a NAT-PT (NAT-PT) performing apparatus for performing packet forwarding between an IPv6 node and an IPv4 node, There are a plurality of NAT-PT performing apparatuses, and each packet processing state information is shared between each NAT-PT performing apparatuses using ICMPv6 redirect messages defined by NDP (Neighbor Discovery Protocol). Interworking method between IPv6 network and IPv4 network. delete 15. The method of claim 14, wherein the ICMPv6 redirect message is A flag bit indicating a packet processing state of the NAT-PT performing apparatus; And And a target address field for storing an address of another NAT-PT performing apparatus adjacent to the NAT-PT performing apparatus. 15. The method of claim 14, wherein the packet processing state of each NAT-PT performing apparatus is A predetermined threshold value indicating a packet processing capacity that can be processed by the NAT-PT is the current packet processing state obtained by the size of the IPv6-IPv4 address translation mapping table included in the NAT-PT performing apparatus or the degree of use of the mapping table. An interworking method between an IPv6 network and an IPv4 network, characterized by whether or not it is abnormal. 15. The method of claim 14, wherein the packet processing state of each NAT-PT performing apparatus is Characterized in that the current packet processing state obtained by the use state of the IPv4 address pool provided in the NAT-PT performing apparatus is greater than or equal to a predetermined threshold indicating the packet processing capacity that the NAT-PT can process. Interworking method between IPv6 network and IPv4 network. In the NAT-PT method performed in the NAT-PT performing apparatus, (a) receiving an IPv6 packet and determining whether the received IPv6 packet can be processed according to a current packet processing state; And (b) if it is determined that the received IPv6 packet can be processed, the address of the IPv6 node which has transmitted the IPv6 packet from the IPv4 address pool storing the available IPv4 address is mapped to the IPv4 address and the received IPv6 packet; If it is determined that the received header is unable to process the received IPv6 packet, it is different from the NAT-PT performing apparatus to the IPv6 node that has transmitted the IPv6 packet through a predetermined message. And instructing a NAT-PT executing apparatus to transmit the IPv6 packet. The method of claim 19, wherein step (a) The received IPv6 is determined according to whether the value of the current packet processing of the NAT-PT performing apparatus depends on the size of the mapping table, the degree of use of the mapping table, or the value obtained by the state of use of the IPv4 address pool. NAT-PT performing method characterized in that it is determined whether the packet can be processed. delete The method of claim 19, And the predetermined message is a redirect message of ICMPv6. The method of claim 22, wherein the redirect message is A flag bit indicating a packet processing state of the NAT-PT performing apparatus; And NAT-PT performing method characterized in that it comprises a target address field for storing the address of the other NAT-PT performing apparatus neighboring the NAT-PT performing apparatus. 20. The method of claim 19, wherein step (b) NAT-PT method, characterized in that for converting the received IPv6 packet header using the stateless IP / ICMP Translation Algorithm (SIIT) to the IPv4 packet header when the determination result can be processed. Program to execute the interworking method between IPv6 network and IPv4 network in IPv6-IPv4 interworking system equipped with NAT-PT (NAT-PT) execution device that performs packet forwarding between IPv6 node and IPv4 node. In a computer-readable recording medium, There are a plurality of NAT-PT performing apparatuses, and each packet processing state information is shared between each NAT-PT performing apparatuses using ICMPv6 redirect messages defined by NDP (Neighbor Discovery Protocol). A computer-readable recording medium that records a program for executing an interworking method between an IPv6 network and an IPv4 network on a computer. (a) receiving an IPv6 packet and determining whether the received IPv6 packet can be processed according to a current packet processing state; And (b) if it is determined that the received IPv6 packet can be processed, the address of the IPv6 node which has transmitted the IPv6 packet from the IPv4 address pool storing the available IPv4 address is mapped to the IPv4 address and the received IPv6 packet; If it is determined that the received header is unable to process the received IPv6 packet, it is different from the NAT-PT performing apparatus to the IPv6 node that has transmitted the IPv6 packet through a predetermined message. And instructing a NAT-PT executing apparatus to transmit the IPv6 packet. A computer-readable recording medium having recorded thereon a program for executing a NAT-PT performing method on a computer. In a network having at least one device for performing IP packet forwarding between an IPv6 node and an IPv4 node, the interworking method between a network composed of the IPv6 node and a network composed of the IPv4 node, (a) receiving a DNS message for finding an IPv4 address for a destination domain name and delivering it to a DNSv4 server to receive an IPv4 address for the destination domain name; (b) converting the received IPv4 address into an IPv6 address by attaching a predetermined prefix to the received IPv4 address; And (c) transmitting the converted IPv6 address information to the IPv6 node. The method of claim 27, (d) interworking between the IPv6 network and the IPv4 network, further comprising transmitting a data packet using the received IPv6 node address as a destination address. 29. The method of claim 27, wherein the predetermined prefix is Interworking method between an IPv6 network and an IPv4 network, characterized in that the prefix sequentially assigned to any one of the prefixes assigned to the devices for performing IP packet forwarding. 29. The method of claim 27, wherein the predetermined prefix is A method for interworking between an IPv6 network and an IPv4 network, wherein the load information of the devices that perform IP packet forwarding is received through a predetermined message, and the prefix is assigned to the device having the least load. The method of claim 30, wherein the predetermined message is An interworking method between an IPv6 network and an IPv4 network using a code field of an ICMPv6 redirect message and a QType field of reply data. In the interworking apparatus for interworking between the network consisting of the IPv6 node and the network consisting of the IPv4 node of the network having one or more devices for performing IP packet forwarding between an IPv6 node and an IPv4 node, A DNS message receiver for receiving a DNS message for finding an IPv4 address for a destination domain name; An IPv4 address receiving unit for transmitting the received DNS message to a DNSv4 server and receiving an IPv4 address for the destination domain name; An address conversion unit converting the received IPv4 address into an IPv6 address by attaching a predetermined prefix to the received IPv4 address; And An interworking device between an IPv6 network and an IPv4 network, characterized in that it comprises a transmission unit for transmitting the converted IPv6 address information to the IPv6 node. 33. The method of claim 32, wherein the predetermined prefix is An interworking device between an IPv6 network and an IPv4 network, wherein the prefix is a prefix sequentially assigned to any one of the prefixes assigned to the devices for performing IP packet forwarding. 33. The method of claim 32, wherein the predetermined prefix is Interworking device between an IPv6 network and an IPv4 network, characterized in that the load information of the devices performing the IP packet transmission via a predetermined message, the prefix assigned to the device with the least load. 35. The method of claim 34 wherein the predetermined message is An interworking device between an IPv6 network and an IPv4 network, using a code field of an ICMPv6 redirect message and a QType field of reply data.

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