JP3017217B1 - IPv4-IPv6 conversion device - Google Patents

Abstract

Abstract: An IPv4-only storage of the sum of checksum values of one fragment packet and each fragment packet is provided.
The storage area required for IPv6 conversion is reduced. SOLUTION: A checksum in an upper layer protocol header of a fragment packet subjected to header conversion by a header conversion unit 21 is calculated, the result is added to a value already stored, and a checksum value storage unit 32 stores the result. Check sum recalculation means 22 is provided, and transmission / save control means 23
When all the fragment packets have arrived, the checksum value in the checksum value storage unit 32 is substituted for the upper layer protocol checksum of the fragment packets in the fragment packet storage unit, and the fragment packets are transmitted.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an Internet Protocol (hereinafter referred to as "IP") packet having an Internet Protocol version 4 (hereinafter referred to as IP).
v4) and Internet Protocol version 6 (hereinafter IPv6) from one to the other, so that nodes on an IPv4 network can
The present invention relates to an IPv4-IPv6 translator that enables communication with a node on a v6 network.

[0002]

2. Description of the Related Art Among transmission control protocol / internet protocol (hereinafter referred to as TCP / IP) communication technologies, IP, which is the most basic protocol, provides an unreliable connectionless datagram transfer service. The currently widespread IP is IPv4, and this IP uses an IP address to identify a node on a network. This IP address is
Header of IP packet exchanged between nodes (IP
In the header, the “source address” for identifying the sender and the “destination address” for identifying the recipient are stored. Incidentally, in IPv4, the IP address is 32 bits long.

[0003] On the other hand, with the spread of the Internet, the number of nodes connected to the network has increased rapidly, leading to a shortage of IP addresses. This is generally called an IP address exhaustion problem. To solve this depletion problem, a new version of IP, IPv6, has been proposed. In IPv6, since the IP address is extended to a 128-bit length, the number of nodes that can be connected to the network can be dramatically increased. However, since there is no compatibility between IPv4 and IPv6, I
Nodes on the Pv4 network and nodes on the IPv6 network cannot communicate directly with IP. In addition, since transition from IPv4 to IPv6 still takes time, supporting communication in a network environment in which both nodes coexist has become an important issue in the future.

On the other hand, in such a network environment, a method in which a node on an IPv4 network and a node on an IPv6 network communicate via an IPv4-IPv6 conversion device is disclosed in Japanese Patent Application Laid-Open No. H10-154994,
JP-A-10-136052, JP-A-10-230
No. 72 is proposed. IETF (Int
ernet Engineering Task Fo
rse) Internet-Draf
ts “Network Address Trans
lation-Protocol Translati
“on (NAT-PT)”, a basic method for address translation and protocol translation has been proposed. In these systems, when the IPv4-IPv6 translator relays an IP packet, it converts the IP header from the IPv4 format to the IP address.
By converting the format from the IPv6 format to the IPv6 format or from the IPv6 format to the IPv4 format, communication between the IPv4 node and the IPv6 node is enabled.

[0005]

However, in such a conventional IPv4-IPv6 conversion apparatus, when converting an IP header between IPv4 and IPv6, a transmission control protocol (TCP) and a user datagram protocol (UDP) are used. ), A checksum value in an upper layer protocol header such as Internet Control Message Protocol (ICMP) must be recalculated and rewritten. If an IPv4 packet or an IPv6 packet is input to the IPv4-IPv6 translator as a plurality of fragments, the packet is once assembled in the translator, an original packet is created, and the upper layer protocol header is checked. It is necessary to update the sum, and the IPv4-IPv6 translation device needs to hold the fragment packets until all the fragment packets arrive, and a large storage area is required due to an increase in the amount of communication. There were challenges.

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problem, and calculates a checksum in an upper layer protocol header of a fragmented IP packet and processes the fragmented packet without reorganizing it. -IPv4 that can reduce the required storage area
6 It is intended to obtain a conversion device.

[0007]

To achieve the above object,
In the IPv4-IPv6 translating apparatus according to the first aspect of the present invention, a portion other than the IP header of the received original IP packet is divided and fragmented, and an IP header copied from the original IP packet is added to these portions. Header converting means for converting a plurality of fragmented packets from one of an IPv4 format header and an IPv6 format header to the other, and calculating a checksum in an upper layer protocol header of the fragmented packet which has been header-converted by the header converting means; Checksum recalculating means for adding the result to a value already stored and storing the result in a checksum value storage unit. The transmission / storage control means includes an upper layer protocol header in the fragment packet. If it is included, this fragment packet is stored in the fragment packet storage unit, When a single packet arrives, the checksum value in the checksum value storage unit is substituted into the upper layer protocol checksum of the fragment packet in the fragment packet storage unit, and then the fragment packet is transmitted. .

[0008] Further, according to the second aspect of the present invention, IPv4-
The IPv6 translator holds the position and length from the beginning on the original IP packet before fragmentation of the fragment packet obtained from the header translator, so that the arrival status of the fragment packet can be referred to. A fragment position recording unit is provided.

[0009] Further, the IPv4 according to the third aspect of the present invention.
The IPv6 translator uses the upper layer protocol as a transmission control protocol.

[0010] Further, according to the fourth aspect of the present invention, IPv4-
Prior to receiving the fragment packet, the IPv6 translator initializes a variable for recording the position of the received fragment packet and a variable for holding an addition result of the checksum value of each fragment packet, The data is stored in the fragment position recording unit and the checksum value storage unit.

[0011] Further, according to the fifth aspect of the present invention, the IPv4-
The IPv6 translator is provided with an address translator, whereby a portion of the received original IP packet other than the IP header is divided and fragmented, and an IP header copied from the original IP packet is added thereto. A plurality of fragmented packets are converted from one of an IPv4 format address and an IPv6 format address to the other.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing an IPv4-IPv6 conversion device, which includes a receiving device 1 for receiving an IP packet, a data processing device 2 operated under program control, and a storage device 3 for storing various information.
And a transmitting device 4 for transmitting an IP packet. Of these, the receiving device 1 is connected to the I
The P packet is received and passed to the data processing device 2. The receiving apparatus 1 receives an IPv4 packet when the receiving apparatus 1 is connected to an IPv4 network, and receives an IPv4 packet when the receiving apparatus 1 is connected to an IPv6 network.
Receive a v6 packet.

The data processing device 2 includes a header conversion unit 21, a checksum recalculation unit 22, and a transmission / save control unit 23. Among these, the header conversion means 21 converts the header format of the IP packet passed from the receiving device 1. That is, when the packet passed from the receiving device 1 is an IPv4 packet, the packet is converted from an IPv4 format header to an IPv6 format header, and
If the packet passed from is an IPv6 packet,
The header in the v6 format is converted into a header in the IPv4 format. Further, the header conversion unit 21 records the position information of the fragment packet, which is the received IP packet, in the fragment position recording unit 31. The fragment packet that has undergone the header conversion process is passed to the checksum recalculation means 22.

[0014] The checksum recalculation means 22 comprises an IP
The checksum in the upper layer protocol header is recalculated for the packet whose header has been converted to the v4 or IPv6 format. The checksum in the upper layer protocol header must be calculated for the entire IP packet, and when the IP header is converted, the contents of the header are changed, so that the checksum must be recalculated. Also,
If the packet is fragmented, it is necessary to calculate the partial checksum for each fragment, sum them, and calculate the overall checksum. Therefore, the result of the recalculation is stored while being added to the checksum value storage unit 32. The fragment packet for which the checksum recalculation has been completed is passed to the transmission / storage control means 23.

The transmission / save control means 23
Determines whether to store the fragment packet in the IPv4-IPv6 translation device or to transmit the fragment packet onto the network through the transmission device 4, and executes the determination. When storing, the fragment packet is stored in the fragment packet storage unit 33, and when transmitting, the fragment packet is passed to the transmitting device 4. In addition, with reference to the fragment packet arrival status stored in the fragment position recording unit 31, it is determined whether or not to transmit the fragment packet stored in the fragment packet storage unit 33, and the process is executed.

The storage device 3 includes the fragment position recording unit 31, a checksum value storage unit 32, and a fragment packet storage unit 33. Among these, the fragment position recording unit 31 is a place where the position information of the received fragment packet is recorded. The content to be recorded is the offset value of each fragment packet, that is, the position and length from the head on the original IP packet before fragmentation. The arrival status can be referenced. The fragment position recording unit 31 is referred to by the transmission / save control unit 23 in order to determine whether all fragment packets have been received. Further, the checksum value storage section 32 stores the value calculated by the checksum recalculation means 22. Further, the checksum value stored here is referred to by the transmission / storage control means 23 when transmitting the fragment packet stored in the fragment packet storage unit 33.

Further, the fragment packet storage unit 33 stores a fragment packet including an upper layer protocol header portion (strictly, a checksum field in the upper layer protocol header) in a series of fragmented packets. A place to save. This fragment packet is held until a series of fragment packets are received and the header conversion process is completed. Since the checksum value in the upper layer protocol header is not determined until all the fragment packets are received, the fragment packet including the checksum field needs to be held until the last fragment packet arrives. As a result, the transmission order of the fragments transmitted from the IPv4-IPv6 header translator is different from that at the time of reception, but in IP, the problem does not occur due to the change in the transmission order of the fragment packets. The transmission device 4 receives the IP packet on which the header conversion and the checksum recalculation processing are completed from the transmission / save control unit 23 and transmits the IP packet over the network.

Next, the operation will be described in detail. First, fragmentation of an IPv4 packet will be described. Referring to FIG. 2, the original IPv4 packet P0 has I
The portion other than the Pv4 header (the upper layer header and the data portion) is divided, and the above-mentioned IPv4
4 packet P0 is copied with an IPv4 header, and fragmented packets P1, P2,. . . , Pn.

Next, the IP for these fragmented packets is
The processing contents of the v4-IPv6 conversion device will be described. For the sake of simplicity, here, as shown in FIG. 2, a group of IPv4 fragment packets P1, P2,. . . P
Focus on n only, and do not discuss the handling of other packets. The upper layer protocol of the IPv4 packet P0 is TCP. TCP is IPv4 packet P0
Requires a global checksum calculation.

FIG. 3 is a flowchart showing a conversion processing procedure by the IPv4-IPv6 conversion device. According to this, first, before receiving a fragmented IPv4 packet, two initializations are performed (step A1). The first is to initialize a variable A for recording the position of the received fragment packet, and this variable is stored in the fragment position recording unit 31. The second is to initialize a variable B for holding the addition result of the checksum value of each fragment packet, and this variable is stored in the checksum value storage unit 32. Then, the receiving device 1 transmits the fragmented packets P1, P2,. . . , Pn one by one (Step A2), and sequentially passes them to the data processing device 2. The fragment packet passed to the data processing device 2 is
In step 1, the header format is converted from the IPv4 format to the IPv6 format (step A3). As shown in FIGS. 4 (a) and 4 (b), header conversion from IPv4 to IPv6
This is performed by replacing the IPv4 header with the IPv6 header for each of the cases including and not including the P header. Further, the header conversion means 21 records the position information of the fragment packet with respect to the original IPv4 packet P0 before fragmentation as the variable A in the fragment position recording unit 31 (step A4).

Next, a checksum value for the upper layer protocol (TCP) of the fragment packet subjected to the header conversion is calculated, added to the variable B, and stored in the checksum value storage unit 32 (step A5). The checksum in the TCP header is calculated by dividing the entire IP packet into 2 bytes and summing up the checksums in each section. Therefore, the checksum value of each fragment packet is individually calculated, and the checksum values of the fragment packets are summed to calculate the checksum as a whole. According to the rules of the IP, the packet is not divided at a position other than the 2-byte boundary in the fragmentation of the packet, so that the checksum calculation can be completed by one fragmented packet. The checksum is calculated by the first fragment packet P1 and the other fragment packets P2,. . . , Pn. In the case of P1, the entire fragmented packet including the IPv4 header is to be calculated, while
2,. . . , Pn, only data fragments excluding the IPv4 header are to be calculated.

Subsequently, it is checked whether a TCP header (strictly, a TCP checksum field) is included in the fragment packet (step A6). If the TCP packet is not included, the fragment packet is transmitted from the transmitting device 4. The packet is transmitted (step A7), and if it is included, the fragment packet is stored in the fragment packet storage unit 33 (step A).
8). Next, the variable A of the fragment position recording unit 31 is checked, and if all fragment packets have been received (step A
9), the TCP checksum value of the fragment packet stored in the fragment packet storage unit 33 is updated with the value of the variable B stored in the checksum value storage unit 32, and this fragment is transmitted (step A10). .

Next, another embodiment of the present invention will be described with reference to the flowchart of FIG. FIG. 5 differs from FIG. 3 in that the format of the header is converted from IPv6 to IPv4. Header format from IPv6 to IPv4
In the case of conversion to IPv6, it is necessary to recalculate the checksum in the TCP header which is an upper layer protocol.
The same fragment packet processing method as in the case of converting from IPv4 to IPv6 can be used. FIG. 6 shows still another embodiment of the present invention. FIG. 6 differs from FIG. 3 in that only the IP address is changed without changing the format of the IP header. Regarding IPv4 address conversion technology, RFC16 issued by IETF
31 The IP Network Address
Translator (NAT).
By using this technology, even when the IP address in the IPv4 header is converted, it is necessary to recalculate the checksum in the upper layer protocol header.
The same fragment packet processing method as in the case of Pv4-IPv6 conversion can be applied.

[0024]

As described above, according to the present invention, a plurality of fragment packets to which an IP header copied from an original IP packet is attached can be converted into an IPv4 format and an IP packet.
A v6 format header or address is converted from one to the other, the checksum in the upper layer protocol header of the converted fragmented packet is calculated, and the result is added to the already stored value to store the checksum value. Department,
When the fragment packet includes an upper layer protocol header, the transmission / storage control means causes the fragment packet to be stored in a fragment packet storage unit, and when all the fragment packets arrive, the checksum After the checksum value in the value storage unit is substituted into the upper layer protocol checksum of the fragment packet in the fragment packet storage unit, the fragment packet is transmitted, so that the fragmented IP packet can be transmitted in IPv4 and IPv4.
When converting between 6, it is necessary to store only the sum of the checksum values of one fragment packet and each fragment packet without storing all the fragments received until the last fragment packet arrives. Therefore, the required storage area can be reduced.

[Brief description of the drawings]

FIG. 1 shows an IPv4-I according to an embodiment of the present invention.
It is a block diagram showing a Pv6 conversion device.

FIG. 2 is an explanatory diagram showing fragmentation of an IP packet according to the present invention.

FIG. 3 is a flowchart showing a conversion procedure from IPv4 to IPv6 according to the present invention.

FIG. 4 is an explanatory diagram showing a header conversion method from an IPv4 format to an IPv6 format according to the present invention.

FIG. 5 is a flowchart showing another conversion procedure from IPv4 to IPv6 according to the present invention.

FIG. 6 is a flowchart showing another conversion procedure from IPv4 to IPv6 according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 21 Header conversion means 22 Checksum recalculation means 23 Transmission / save control means 31 Fragment position recording part 32 Checksum value storage part 33 Fragment packet storage part

──────────────────────────────────────────────────の Continued on the front page (58) Fields surveyed (Int. Cl. ⁷ , DB name) H04L 12/28 H04L 12/56 H04L 12/66 H04L 29/06 G06F 11/10 310 INSPEC (DIALOG) JICST file (JOIS)

Claims (5)

(57) [Claims] 1. An IPv4 that enables communication between a node on an IPv4 network and a node on an IPv6 network by converting an IP header of an IP packet from one of an IPv4 format and an IPv6 format to the other.
In the IPv6 translator, a portion of the received original IP packet other than the IP header is divided and fragmented, and a plurality of fragmented packets to which the IP header copied from the original IP packet is attached are added to an IPv4 Header converting means for converting one of the header of the IPv6 format and the header of the IPv6 format into the other, and calculating the checksum in the upper layer protocol header of the fragmented packet which has been header-converted by the header converting means, and has already calculated the result. A checksum recalculating means for adding the stored value to the checksum value storage unit and storing it in a checksum value storage unit; and when the fragment packet includes an upper layer protocol header, the fragment packet is stored in the fragment packet storage unit. And when all the fragmented packets arrive, the checker A transmission / save control unit for transmitting the fragment packet after substituting the checksum value in the value storage unit for the upper layer protocol checksum of the fragment packet in the fragment packet storage unit; IPv6 translator. 2. In order to make it possible to refer to the arrival status of the fragment packet, the position and length from the head of the fragment packet obtained from the header conversion means on the original IP packet before fragmentation are held. The IPv4-IPv6 conversion device according to claim 1, further comprising a fragment position recording unit. 3. The IPv4 according to claim 1, wherein the upper layer protocol is a transmission control protocol.
An IPv6 translator. 4. A variable for recording a position of a received fragment packet and a variable for holding an addition result of a checksum value of each fragment packet are initialized before receiving the fragment packet. The IPv4-IPv6 conversion apparatus according to claim 1, wherein the data is stored in the fragment position recording unit and the checksum value storage unit. 5. An IPv4 that enables communication between a node on an IPv4 network and a node on an IPv6 network by converting an IP header of an IP packet from one of an IPv4 format and an IPv6 format to the other.
In the IPv6 translator, a portion of the received original IP packet other than the IP header is divided and fragmented, and a plurality of fragmented packets to which the IP header copied from the original IP packet is attached are added to an IPv4 Translation means for translating from one of an address in the form of IPv6 and an address in the form of IPv6 to the other, and calculates a checksum in the upper layer protocol header of the fragmented packet which has undergone the address translation by the address translation means, and the result is already calculated. A checksum recalculating means for adding the stored value to the checksum value storage unit and storing it in a checksum value storage unit; and when the fragment packet includes an upper layer protocol header, the fragment packet is stored in the fragment packet storage unit. And when all the fragment packets arrive, the A transmission / save control unit for transmitting the fragment packet after substituting the checksum value in the checksum value storage unit into the upper layer protocol checksum of the fragment packet in the fragment packet storage unit. An IPv6 translator.