WO2011103820A2

WO2011103820A2 - Method and apparatus for network address translation

Info

Publication number: WO2011103820A2
Application number: PCT/CN2011/072863
Authority: WO
Inventors: 徐靖
Original assignee: 华为技术有限公司
Priority date: 2011-04-15
Filing date: 2011-04-15
Publication date: 2011-09-01
Also published as: WO2011103820A3; CN102232288A

Abstract

The invention relates to a method and an apparatus for Network Address Translation (NAT). The method includes that: a NAT device receives a data package transmitted from an intranet host, parses the data package, obtains a first source Internet Protocol (IP) address, a first source port, a first destination IP address and a first IP data package Identifier (IPID) contained in the data package, performs processing, which includes the steps of translating the first source IP address into a second source IP address and translating the first source port into a second source port, for the first source IP address and the first source port in the data package, performs processing for the first IPID in the data package, and transmits the processed data package according to the first destination IP address. The method and apparatus for network address translation proposed in the invention can modify the IPIDs of messages at the same time when the address translation is performed at the NAT device, and thus ensure that no mistake will occur when a destination device performs message recombination.

Description

Network address translation method and device

Technical field

The present invention relates to the field of network technologies, and in particular, to a network address translation method and apparatus. Background technique

In the prior art, due to address planning and the like, IPv4 (Internet Protocol version 4) addresses are rapidly exhausted, for which the IETF (Internet Engineering Task Force) is in an IPv4 address. A private IP address segment is defined, including: ΙΟ.χ.χ.χ, 172.16.xx-172.31.xx, 192.168.xx. These private IP addresses can be used to build private networks (internal networks), such as companies and enterprise internal networks, thus greatly reducing the need for public network addresses, and to some extent, solving the problem of public network IP address exhaustion, but these private The IP address cannot be routed on the public network (Internet). In order to enable the private network host to access the host/server on the public network, a NAT (Network Address Translation) device is deployed at the private network exit to convert between the private IP address and the public IP address.

There are three ways to implement NAT, namely, Static Nat, Dynamic Nat, and Port Address Translation (PAT). Currently, the most widely used network is the port multiplexing mode. Port multiplexing converts "private IP address + port number" into "public network IP address + new port number". When converting the private IP address of the internal network to the public IP address, multiple internal privates can be used. The IP address is replaced with the same public IP address, but with different ports. Ports are multiplexed. All hosts on the internal network can share a valid public IP address to access the Internet. This saves public IP address resources and hides all hosts in the network. Attack from the internet.

At present, most of the traffic on the network is based on the TCP (Transmission Control Protocol) or UDP (User Datagram Protocol) protocol. The quintuple is the source IP address + source port number (TCP or UDP port number) + destination IP address + destination port number + IP protocol number can uniquely identify a traffic. In network data transmission, when the length of the packet exceeds the MTU (Maximum Transmission Unit) of the line, the packet is fragmented so that the length of each fragmented packet does not exceed the MTU of the line. After the TCP or UDP packet is fragmented, only the first packet has a TCP or UDP header. The subsequent fragment packet has only an IP header. There is no TCP or UDP header, that is, only the first fragment of the stationery active port number and destination. Port number. Subsequent fragments do not have a source port number and a destination port. The destination device, such as the server, generally performs packet reassembly based on the triplet: source IP address + destination IP address + IP packet identifier (IPID). Since the identifiers of the IP packets sent by the source host are generally incremented one by one, the identifiers of the IP packets sent by different source hosts may be identical. After NAT address replacement, multiple different streams (determined by quintuple) may have the same source IP address and destination IP address, and these packets also have the same IPID, in which case the destination device An error occurs when the packet is reorganized. Summary of the invention

To overcome the problems in the prior art, embodiments of the present invention provide a network address translation method and apparatus, so as to ensure that no error occurs when the destination device performs packet reassembly.

An embodiment of the present invention provides a network address translation method, where the method includes: a network address translation NAT device receives a data packet sent by an intranet host; parses the data packet, and obtains a first source Internet protocol included in the data packet. The IP address, the first source port, the first destination IP address, and the identifier IPID of the first IP data packet; processing the first source IP address and the first source port in the data packet, including: converting the first source IP address For the second source IP address, converting the first source port to the second source port; processing the first IPID in the data packet; and transmitting the processed data packet according to the first destination IP address.

An embodiment of the present invention further provides a network address translation apparatus, where the apparatus includes:

a receiving unit (501), configured to receive a data packet sent by an intranet host;

The parsing unit (502) is configured to parse the data packet, and obtain the first source Internet Protocol IP address, the first source port, the first destination IP address, and the identifier IPID of the first IP data packet included in the data packet;

The address conversion unit (503) is configured to convert the first source IP address in the data packet to the second source IP address, and convert the first source port to the second source port;

An IPID processing unit (504), configured to process the first IPID in the data packet;

The sending unit (505) is configured to send the processed data packet to the destination IP address.

The network address translation method and device provided by the present invention can simultaneously process the IPID of the data packet when the address is replaced on the NAT device, so that the destination device does not generate an error when the data packet is reassembled. DRAWINGS

The drawings described herein are provided to provide a further understanding of the embodiments of the invention, and are in no way In the drawing:

FIG. 1 is a schematic diagram of an application scenario provided by an embodiment of the present invention;

2 is a flowchart of a network address translation method according to an embodiment of the present invention; 3 is a flowchart of a network address translation method according to another embodiment of the present invention;

4 is a flowchart of a network address translation method according to another embodiment of the present invention;

FIG. 5 is a block diagram of a network address translation apparatus according to an embodiment of the present invention; FIG.

6a, 6b are block diagrams of a network address translation apparatus according to another embodiment of the present invention;

7a and 7b are block diagrams of a network address translation apparatus according to another embodiment of the present invention. detailed description

In order to make the objects, technical solutions, and advantages of the embodiments of the present invention more clearly, the embodiments of the present invention are further described in detail below in conjunction with the embodiments and drawings. The illustrative embodiments of the invention and the description thereof are intended to be illustrative of the invention, and are not intended to limit the invention.

1 is a schematic diagram of an application scenario of the embodiment of the present invention. As shown in FIG. 1, in the prior art, the intranet hosts 101 and 102 access the public network server 104 through the NAT device 103, wherein the address of the intranet host 101 is 10.1. 1.100, the address of the intranet host 102 is 10.1.1.200, and the public network address of the public network server 104 is

211.100.7.34. The NAT device 103 assigns the same public IP address to the intranet hosts 101 and 102.

162.105.178.65, and different port numbers 16384 and 16400 are assigned to the intranet hosts 101 and 102 respectively, so the public network server 104 can distinguish the traffic of the two hosts.

When the length of the packet sent by the intranet hosts 101 and 102 to the public network server 104 exceeds the MTU of the line, the packet is divided into multiple fragments that do not exceed the MTU. In the prior art, after the packet sent by the intranet host 101 or 102 is fragmented, only the first piece of the stationery active port number is 16384 or 16400, and the subsequent fragment does not include the source port number. The public network server 104 can only perform packet reassembly according to the triplet: source IP address 162.105.178.65, destination IP address 211.100.7.34, and IPID.

When the IDs of the IP packets sent by the intranet hosts 101 and 102 are the same, the subsequent fragments of the intranet hosts 101 and 102 received by the public network server 104 have the same source IP address 162.105.178.65, the same purpose. The IP address is 211.10.0.7.34 and the same IPID. Therefore, the public network server 104 generates an error when performing packet reassembly, and cannot distinguish the fragmented packets of the hosts 101 and 102. 2 is a flowchart of a network address translation method according to an embodiment of the present invention. As shown in FIG. 2, the network address translation method includes:

S201. The NAT device receives a data packet sent by an intranet host. S202. Parse the data packet, and obtain a first source IP address, a first source port, a first destination IP address, and a first IPID included in the data packet.

S203: Processing the first source IP address and the first source port in the data packet, including: converting the first source IP address in the data packet to the second source IP address, and converting the first source port to the second source port.

In the embodiment of the present invention, the NAT device allocates a public network IP address and a new port to the data packet sent by the intranet host, and converts the private network IP address and the source port in the data packet sent by the intranet host into the public network IP address. And the new end π.

5204. Process the first IPID in the data packet.

In the embodiment of the present invention, the NAT device processes the first IPID in the data packet, so that the IPID does not repeat when the data packet sent by the NAT device to the destination device has the same source IP address and destination IP address. Therefore, when the destination device reassembles the received data packet, no reorganization error occurs due to the duplicate IPID.

5205. Send the processed data packet according to the first destination IP address.

The network address translation method in the embodiment of the present invention, when the address replacement is performed on the NAT device, simultaneously processes the IPID of the data packet, so that the destination device does not generate an error when the data packet is reassembled. FIG. 3 is a flowchart of a network address translation method according to another embodiment of the present invention. As shown in FIG. 3, the network address translation method includes:

5301. The NAT device receives a data packet sent by an intranet host.

Taking the scenario shown in FIG. 1 as an example, the NAT device 103 can receive at least one of the intranet hosts 101 and 102 and send the data packet to the public network server 104. For the sake of simplicity, the NAT device 103 receives the data packets sent by the intranet hosts 101 and 102 to the public network server 104 as an example.

S302: Parse the data packet, and obtain a first source IP address, a first source port, a first destination IP address, and a first IPID included in the data packet.

For example, the NAT device 103 parses the received data packets sent by the intranet hosts 101 and 102 to the public network server 104, and obtains the first source IP address, the first source port, the first destination IP address, and the data packet. The first IPID, where the intranet host 101 sends the data packet, the first source IP address is 10.1.1.100, the first source port is 1025, the first destination IP address is 211.10.0.7.34, and the first IPID is 9527. Optionally, the first destination port 24 included in the data packet may also be obtained. S303. Convert the first source IP address in the data packet to the second source IP address, and convert the first source port to the second source port.

For example, the NAT device 103 allocates a public network IP address and a new port to the data packet sent by the intranet host 101, and converts the first source IP address 10.1.1.100 and the first source port 1025 in the data packet into a public network IP address, respectively.

162.105.178.65 and the new port 16384.

5304. Determine whether there is an IPID storage table corresponding to the second source IP address and the first destination IP address. If the corresponding IPID storage table does not exist, execute S305. If the corresponding IPID storage table exists, execute S306.

For example, the NAT device 103 determines whether there is an IPID storage table corresponding to the public network IP address 162.105.178.65 and the first destination IP address 211.100.7.34.

S305. Establish an IPID storage table corresponding to the second source IP address and the first destination IP address.

For example, when the NAT device 103 determines that there is no IPID storage table corresponding to the public network IP address 162.105.178.65 and the first destination IP address 211.10.0.7.34, the NAT device 103 can be based on the public network IP address 162.105.178.65 and the first The destination IP address 211.10.0.7.34 establishes an IPID storage table, which includes a second source IP address (ie, a public network IP address in this example), a first destination IP address, and an IPID (see Table 1 below).

Optionally, in the IPID storage table shown in Table 1, the initial value of the IPID is 0, and the value of the IPID is increased by 1 for each subsequent data packet sent by the NAT device 103. Of course, the initial value may also be set after each transmission. For a data packet, the data of the IPID is decremented by one, which is not limited by the embodiment of the present invention. Further, optionally, the length of the IPID value in the IPID storage table may be set, for example, may be 16 bits, and then returned to the initial value after overflow.

Table 1

5306. Processing the first IPID in the data packet, including: converting the first IPID in the data packet to the second IPID according to the IPID storage table corresponding to the second source IP address and the first destination IP address, where the foregoing The second IPID is the IPID contained in the IPID storage table.

For example, the NAT device 103 determines that there is an IPID storage table corresponding to the public network IP address 162.105.178.65 and the first destination IP address 211.10.0.7.34. As shown in Table 1, the NAT device 103 is based on the public network IP address 162.105. 178.65 The IPID storage table corresponding to the first destination IP address 211.10.0.7.34, and replace the first IPID (9527) in the data packet with the IPID (0) contained in the storage table.

5307. Send the processed data packet according to the first destination IP address. In the embodiment of the present invention, the NAT device 103 sends the processed data packet to the first destination IP address, that is, the public network server 104.

Optionally, after the data packet is sent, in the embodiment of the present invention, the value of the IPID in the IPID storage table may also be incremented or decremented by one.

The network address translation method proposed in the embodiment of the present invention, when performing address replacement on a NAT device, according to

The IPID storage table processes the IPID of the data packet so that the IPID does not overlap, so that when the destination device reassembles the received data packet, no reorganization error occurs due to duplicate IPID. 4 is a flowchart of a network address translation method according to an embodiment of the present invention. As shown in FIG. 4, the network address translation method includes:

5401. The NAT device receives a data packet sent by an intranet host.

Still taking the scenario shown in FIG. 1 as an example, the NAT device 103 receives the data packets sent by the intranet hosts 101 and 102 to the public network server 104.

S402. Parse the data packet, and obtain a first source IP address, a first source port, a first destination IP address, and a first IPID included in the data packet.

For example, the NAT device 103 parses the received data packets sent by the intranet hosts 101 and 102 to the public network server 104, and obtains the first source IP address, the first source port, the first destination IP address, and the data packet. The first IPID, in the IP packet sent by the intranet host 101, the first source IP address is 10.1.1.100, the first source port is 1025, the first destination IP address is 211.10.0.7.34, and the first IPID is 9527.

S403. Convert the first source IP address in the data packet to the second source IP address, and convert the first source port to the second source port.

162.105.178.65 and the new source port 16384.

S404. Determine whether there is an IPID storage table corresponding to the second source IP address and the first destination IP address. If the corresponding IPID storage table does not exist, S405 is performed; if there is a corresponding IPID storage table, S406 is performed.

S405. Establish an IPID storage table corresponding to the second source IP address and the first destination IP address. carried out For example, when the NAT device 103 determines that there is no IPID storage table corresponding to the public network IP address 162.105.178.65 and the first destination IP address 211.10.0.7.34, the NAT device 103 can be based on the public network IP address 162.105.178.65 and the first The destination IP address 211.10.0.7.34 establishes an IPID storage table, which includes a second source IP address (ie, a public network IP address in this example), a first destination IP address, and an IPID (see Table 2 below).

Optionally, in the embodiment of the present invention, for a certain set of IP address pairs (the second source IP address and the first destination IP address), the established IPID storage table may include one or more IPIDs, for example, may be stored. 128 IPIDs.

Table 2

S406. Determine whether the IPID storage table corresponding to the second source IP address and the first destination IP address includes an IPID equal to the first IPID in the data packet. When an IPID equal to the first IPID in the above packet is included, S407 is performed. When the IPID equal to the first IPID in the foregoing data packet is not included, in the embodiment of the present invention, the NAT device 103 acquires the IPID storage table according to the new source IP address 162.105.178.65 and the destination IP address 211.10.0.7.34. The IPID corresponding to the new source IP address and destination IP address,

S407. The processing, by the first IPID in the data packet, the first IPID in the data packet is converted into a second IPID according to the IPID storage table corresponding to the second source IP address and the first destination IP address, where The second IPID is different from the IPID contained in the IPID storage table.

In the embodiment of the present invention, if the IPID stored in the storage table includes an IPID equal to the first IPID in the data packet, it indicates that the first IPID of the data packet may be duplicated with the previously sent data packet, resulting in the public network server. 104 receives the data packet whose source IP address, destination IP address, and IPID are the same, thereby causing an error in reassembly. To avoid such an error, the NAT device 103 converts the first IPID in the data packet to ensure the IPID storage table. The stored IPID is different from the converted second IPID, so that the IPIDs in the recently transmitted N packets do not conflict. For example, when updating the first IPID in the data packet, a random number may be used to allocate a new IPID to the data packet, and at the same time ensure that the new IPID is different from the IPID stored in the IPID storage table. S408: Store the second IPID in the data packet in the IPID storage table corresponding to the second source IP address and the first destination IP address, and execute S410.

The processing of the first IPID in the data packet includes: storing the first IPID in the data packet in the IPID storage table corresponding to the second source IP address and the first destination IP address, and executing S410.

In the embodiment of the present invention, each time a data packet is sent, the IPID of the sent data packet is stored in

In the IPID storage table, N IPIDs can be stored for a new set of source IP addresses and destination IP addresses. For example, N can be set to 128, so that the N most recently used IPIDs can be stored in the IPID storage table.

5410. Send the processed data packet to the first destination IP address.

In the embodiment of the present invention, the NAT device 103 sends the processed data packet to the destination IP address, that is, the public network server 104.

The network address translation method of the embodiment of the present invention, when performing address replacement on the NAT device, processes the IPID of the data packet according to the IPID storage table, so that the IPID does not overlap, thereby ensuring that the destination device reassembles the received data packet. , there will be no reorganization errors due to duplicate IPIDs. FIG. 5 is a block diagram of a network address translation apparatus according to an embodiment of the present invention. As shown in FIG. 5, the network address translation apparatus 500 includes:

The receiving unit 501 is configured to receive a data packet sent by the intranet host.

The parsing unit 502 is configured to parse the data packet, and obtain a first source IP address, a first source port, a first destination IP address, and a first IPID included in the data packet.

The address conversion unit 503 is configured to convert the first source IP address in the data packet to the second source IP address, and convert the first source port to the second source port.

The IPID processing unit 504 is configured to process the first IPID in the data packet.

The sending unit 505 is configured to send the processed data packet to the destination IP address.

The network address translation device of the embodiment of the present invention processes the IPID of the data packet at the same time when the address is replaced on the NAT device, so that the destination device does not generate an error when the data packet is reassembled. Optionally, as shown in FIG. 6a, the foregoing network address translation apparatus may further include:

The first ID determining unit 604 is configured to determine whether there is an IPID storage table corresponding to the second source IP address and the first destination IP address, and if there is no corresponding IPID storage table, triggering the first establishing unit 605; if there is a corresponding The IPID storage table triggers the IPID processing unit 504. The first establishing unit 605 is configured to establish an IPID storage table corresponding to the second source IP address and the first destination IP address.

Optionally, as shown in FIG. 6b, the foregoing IPID processing unit 504 may include:

The first obtaining module 5041 is configured to obtain a second IPID, where the second IPID is an IPID included in an IPID storage table corresponding to the second source IP address and the first destination IP address;

The first conversion module 5042 is configured to convert the first IPID in the data packet to the second IPID.

The network address translation apparatus according to the embodiment of the present invention processes the IPID of the data packet according to the IPID storage table, so that the IPID does not overlap, thereby ensuring that the destination device does not reorganize the IPID when the received data packet is reorganized. error. Optionally, as shown in FIG. 7a, the foregoing network address translation apparatus may further include:

The second ID determining unit 704 is configured to determine whether there is an IPID storage table corresponding to the second source IP address and the first destination IP address, if there is no corresponding IPID storage table, triggering the second establishing unit 705; if there is a corresponding The IPID storage table triggers the IPID processing unit 504.

The second establishing unit 705 is configured to establish an IPID storage table corresponding to the second source IP address and the first destination IP address.

The storage table updating unit 706 is configured to store the first IPID in the data packet in the IPID storage table.

Optionally, as shown in FIG. 7b, the foregoing IPID processing unit 504 may include:

The second obtaining module 5043 is configured to obtain an IPID stored in an IPID storage table corresponding to the second source IP address and the first destination IP address.

The determining module 5044 is configured to determine whether the acquired IPID includes an IPID equal to the first IPID in the data packet, and if so, triggering the second converting module 5045; if not, triggering the storage table updating unit 706.

The second conversion module 5045 is configured to convert the first IPID in the data packet into a second IPID, where the second IPID and the IPID stored in the IPID storage table are different.

The update module 5046 is configured to store the second IPID in the data packet in the IPID storage table.

The network address translation apparatus according to the embodiment of the present invention processes the IPID of the data packet according to the IPID storage table, so that the IPID does not overlap, thereby ensuring that the destination device does not reorganize the IPID when the received data packet is reorganized. error. The above described embodiments of the present invention are further described in detail, and the embodiments of the present invention are intended to be illustrative only. The scope of the protection, any modifications, equivalents, improvements, etc., made within the spirit and scope of the invention are intended to be included within the scope of the invention.

Claims

Claim

A network address translation method, comprising:

Network address translation The NAT device receives the data packet sent by the intranet host;

Parsing the data packet, obtaining a first source Internet Protocol IP address, a first source port, a first destination IP address, and an identifier IPID of the first IP data packet included in the data packet;

Processing the first source IP address and the first source port in the data packet, including: converting the first source IP address to the second source IP address, and converting the first source port to the second source port;

Processing the first IPID in the data packet;

The processed data packet is sent according to the first destination IP address.

The network address translation method according to claim 1, wherein before the processing of the first IPID in the data packet, the method further includes:

It is determined whether there is an IPID storage table corresponding to the second source IP address and the first destination IP address.

The network address translation method according to claim 2, wherein if there is an IPID storage table corresponding to the second source IP address and the first destination IP address, processing the first IPID in the data packet, Specifically, the method includes: converting, according to the IPID storage table corresponding to the second source IP address and the first destination IP address, the first IPID in the data packet to the second IPID, where the second IPID is the second source IP address The IPID contained in the IPID storage table corresponding to the first destination IP address.

The network address translation method according to claim 2, wherein if there is no IPID storage table corresponding to the second source IP address and the first destination IP address, processing the first IPID in the data packet Previously, the method further includes:

Establishing an IPID storage table corresponding to the second source IP address and the first destination IP address;

The processing the first IPID in the data packet includes:

The first IPID in the data packet is converted into a second IPID, and the second IPID is an IPID included in the IPID storage table corresponding to the second source IP address and the first destination IP address.

5. The network address translation method according to claim 2, wherein if there is an IPID storage table corresponding to the second source IP address and the first destination IP address, before processing the first IPID in the data packet The method further includes:

Obtaining an IPID stored in an IPID storage table corresponding to the second source IP address and the first destination IP address;

It is determined whether the acquired IPID includes an IPID equal to the first IPID.

The network address translation method according to claim 5, wherein if the acquired IPID includes an IPID equal to the first IPID, the processing the first IPID in the data packet, specifically The method includes: converting, according to an IPID storage table corresponding to the second source IP address and the first destination IP address, a first IPID in the data packet to a second IPID, where the second IPID is related to the second source IP address and The IPIDs included in the IPID storage table corresponding to the first destination IP address are different.

The network address translation method according to claim 6, wherein after the first IPID in the data packet is converted into the second IPID, the method further includes:

The second IPID in the data packet is stored in the above IPID storage table corresponding to the second source IP address and the first destination IP address.

The network address translation method according to claim 5, wherein if the acquired IPID does not include an IPID equal to the first IPID, the processing the first IPID in the data packet, Specifically, the method includes: storing, in the IPID storage table corresponding to the second source IP address and the first destination IP address, the first IPID in the data packet.

The processing the first IPID in the data packet includes:

The first IPID in the data packet is stored in the IPID storage table corresponding to the second source IP address and the first destination IP address.

10. A network address translation apparatus, wherein the apparatus comprises:

The network address translation device according to claim 10, wherein the device further comprises: The first ID determining unit (604) is configured to determine whether there is an IPID storage table corresponding to the second source IP address and the first destination IP address, if there is no IPID corresponding to the second source IP address and the first destination IP address Storing the table, triggering the first establishing unit (605); if there is an IPID storage table corresponding to the second source IP address and the first destination IP address, triggering the IPID processing unit (504);

The first establishing unit (605) is configured to establish a correspondence with the second source IP address and the first destination IP address.

IPID storage table.

The network address translation device according to claim 11, wherein the IPID processing unit (504) comprises:

The first obtaining module (5041) is configured to obtain a second IPID, where the second IPID is an IPID included in an IPID storage table corresponding to the second source IP address and the first destination IP address;

The first conversion module (5042) is configured to convert the first IPID in the data packet to the second IPID.

The network address translation apparatus according to claim 10, wherein the apparatus further comprises: a second ID determining unit (704), configured to determine whether there is a second source IP address and a first destination IP address The IPID storage table corresponding to the address, if there is no IPID storage table corresponding to the second source IP address and the first destination IP address, triggering the second establishing unit (705); if there is a second source IP address and the first destination IP address The IPID storage table corresponding to the address, triggering the IPID processing unit (504);

The second establishing unit (705) is configured to establish an IPID storage table corresponding to the second source IP address and the first destination IP address;

The storage table updating unit (706) is configured to store the first IPID in the data packet in an IPID storage table corresponding to the second source IP address and the first destination IP address.

The network address translation apparatus according to claim 13, wherein the IPID processing unit (504) comprises:

a second obtaining module (5043), configured to acquire an IPID stored in an IPID storage table corresponding to the second source IP address and the first destination IP address;

a judging module (5044), configured to determine whether the acquired IPID includes the first one of the foregoing data packets

IPID with equal IPID, if included, triggers the second conversion module (5045); if not, triggers the storage table update unit (706);

The second conversion module (5045) is configured to convert the first IPID in the data packet into a second IPID, where the second IPID is stored with the IPID corresponding to the second source IP address and the first destination IP address. The IPIDs stored in the table are not the same;

An update module (5046) for storing the second IPID in the data packet with the second source IP address and the first destination IP address corresponding to the IPID storage table