CN100512228C - Method for realizing communication between IPv4 communication node and mobile node of crossing heterogeneous network - Google Patents

Abstract

The present invention relates to a method for realizing communication between an IPv4 communication node and a mobile node across a heterogeneous network. Specifically, the problem to be solved by the present invention is: the home agent is in the IPv6 network, the communication node is in the IPv4 network, and the mobile node moves from the IPv6 network After reaching the IPv4 network, how to ensure the continuity of the original communication. The present invention is on the basis of existing Mobile IPv4 technology (RFC3344) and Mobile IPv6 technology (RFC3775), by arranging the NAT-PT gateway with MobileIP-ALG between the heterogeneous networks, and surrounding Mobile IP-ALG pair registration, The communication process is carefully designed so that the mobile node can still maintain communication with the communication node in the IPv4 network after switching from the IPv6 network to the IPv4 network, and after the mobile node switches to the IPv4 network, the datagrams sent between it and the communication node The text does not need to go through the IPv6 network, which improves the routing efficiency. In addition, the movement of the mobile node is completely transparent to the communication node.

Description

A method for realizing communication between IPv4 communication nodes and mobile nodes across heterogeneous networks

technical field

The invention relates to the communication field, in particular to a method for realizing communication between an IPv4 communication node and a mobile node across a heterogeneous network.

Background technique

With the development of network technology and the expansion of network scale, IPv4 (Internet Protocol version 4) can no longer meet the requirements of network development. As an alternative version of IPv4, IPv6 (Internet Protocol version 6) can provide a huge address space and has many new features that IPv4 does not have, and has received more and more attention. Due to the small number of IPv4 addresses in our country, the problem of address exhaustion is particularly prominent, and our country is vigorously promoting the research and development of IPv6. On the other hand, as people's demand for mobile communication increases day by day, the research on mobile communication has also reached an unprecedented height.

In order to solve the problem of mobile communication, people have introduced Mobile IP (Mobile IP) technology. A notable feature of Mobile IP technology is that the movement of mobile nodes is transparent to the applications carried on the network layer. To put it simply, the mobile node moves between different networks, and the applications above the transport layer and above the transport layer do not need to change the source address and destination address of the communication, so as to maintain the continuity of communication.

At present, research on Mobile IP technology has achieved certain results. IETF proposed the Mobile IPv4 (defined in RFC3344) protocol and Mobile IPv6 (defined in RFC3775) protocol in 2002 and 2004 respectively, effectively solving the mobile communication problems in pure IPv4 network and pure IPv6 network. However, IPv6 will not replace IPv4 overnight, and IPv4 and IPv6 will coexist for a long time. Therefore, it is of great significance to solve the problem of mobile communication between heterogeneous networks (referred to here as IPv4 and IPv6 networks).

Mobile communication problems in heterogeneous networks generally fall into the following six situations:

1. The mobile node and its home agent are in the IPv6 network, and the communication node is in the IPv4 network;

2. The mobile node and its home agent are in the IPv4 network, and the communication node is in the IPv6 network;

3. The home agent of the mobile node is in the IPv6 network, the communication node is in the IPv4 network, and the mobile node switches from the IPv6 network to the IPv4 network;

4. The home agent of the mobile node is in the IPv6 network, the communication node is in the IPv6 network, and the mobile node switches from the IPv6 network to the IPv4 network;

5. The home agent of the mobile node is in the IPv4 network, the communication node is in the IPv4 network, and the mobile node switches from the IPv4 network to the IPv6 network;

6. The home agent of the mobile node is in the IPv4 network, the communication node is in the IPv6 network, and the mobile node switches from the IPv4 network to the IPv6 network.

Currently, the IETF has not proposed a solution to the above-mentioned problems. Publicly available information shows that domestic units have proposed a solution to the first situation above, and submitted a patent application (the patent publication number is CN1870583A), and for the second, fourth and fifth situations above, We proposed solutions respectively and submitted patent applications (patent application numbers are 200710026298.3, 200710027050.9 and 200710027404.x respectively), but these four solutions are not applicable to the other two situations mentioned above. The object of the present invention is to propose a solution to the above third situation.

As mentioned earlier, IPv6 will coexist with IPv4 for a long time. At present, there are mainly three technologies to support the communication between the nodes in the IPv6 network and the nodes in the IPv4 network, that is, dual-stack technology, tunnel technology and NAT-PT technology.

The basic principle of NAT-PT (Network Address Translation-Protocol Translation) technology is to set up a gateway (called NAT-PT gateway) between the IPv4 network and the IPv6 network to perform address translation and protocol translation on data packets of different protocol versions. Conversion, that is, data packets sent from the IPv4 network to the IPv6 network must be converted into packets in IPv6 format; data packets sent from the IPv6 network to the IPv4 network must be converted into packets in IPv4 format. The NAT-PT gateway is responsible for maintaining an IPv4 address pool and a mapping table of IPv4 addresses and IPv6 addresses. For address translation from IPv6 to IPv4, the NAT-PT gateway allocates an available IPv4 address from the address pool to map the IPv6 address, and records the mapping relationship for the NAT-PT gateway to query in the subsequent communication process; for IPv4 to IPv6 The NAT-PT gateway adds a 96-bit NAT-PT gateway prefix in front of the IPv4 address.

In addition, because the NAT-PT gateway is a device at the network layer, it generally only converts data packets at the network layer, so DNS, FTP and other applications that involve address translation at the application layer cannot pass through the NAT-PT gateway. In order to solve this problem, people add ALG (Application Layer Gateway) to the NAT-PT gateway. For different applications, there are DNS-ALG, FTP-ALG, etc. Combining the network layer conversion function of the NAT-PT gateway with the application layer processing function of the ALG can solve the problem of DNS, FTP, etc. traversing the NAT-PT gateway.

The working principle of implementing DNS query between heterogeneous networks by using a NAT-PT gateway plus DNS-ALG will be described below with an example in conjunction with FIG. 1 .

As shown in Figure 1, node A on the IPv4 network needs to communicate with node B on the IPv6 network. Node A needs to first use the domain name of node B to query the IP address of node B (in IPv4 format). This process requires the help of a DNS server. Finish.

For convenience of description, it is assumed that both the IPv4 network and the IPv6 network have only one DNS server, which are DNS server A and DNS server B respectively. The domain name of node B is www.abc.com, and its IPv6 address is 2001::1.

Node A wants to query the IP address of node B. First, it sends a DNS query request to DNS server A. DNS server A finds that there is no record of the above domain name, so it queries DNS server B. DNS server B finds the record of the above domain name, interprets it as IPv6 address 2001::1, and sends a reply message to DNS server A. When the response message passes through the NAT-PT gateway, the NAT-PT gateway finds an available IPv4 address (assumed to be 202.116.78.10) from its maintained address pool as the IPv4 address of node B, and creates a mapping record. The modified reply message is returned to node A through the original route, so node A can communicate with node B through 202.116.78.10.

If node B wants to query the IP address of node A, the process is roughly the same. When the response message is returned, the NAT-PT gateway will add a 96-bit NAT-PT gateway prefix in front of the IPv4 address of node A as the IPv6 address of node A.

The present invention relates to Mobile IPv4 technology. The following describes the basic principles of Mobile IPv4 in combination with Figure 2 and RFC3344:

1. Mobile agents indicate their existence through agent advertisement messages. The mobile node can also optionally request the mobile agent on the link to send it an agent advertisement message through an agent request message.

2. The mobile node receives the mobile agent advertisement message, and judges whether it is in the home network or a foreign network according to the message.

3. If the mobile node finds itself in the home network, it will work in the same way as a common fixed node; if the mobile node finds itself returning to the home network from a foreign network, it will log out to the home agent.

4. If the mobile node finds itself moving to a foreign network, it obtains a care-of address from the foreign network. The care-of address can be assigned by the foreign agent, or can be obtained through DHCP and other methods.

5. The mobile node registers the new care-of address with its home agent. Registration request messages and registration response messages generally go through foreign agents.

6. When the mobile node sends a data message to the communication node, it generally sends the data message directly to its communication node through the standard IP routing mechanism. When the router of the foreign network where the mobile node is located has "Ingress Filtering" (Ingress Filtering) When functioning, the mobile node can also first send the data message to the home agent through the reverse tunnel, and then the home agent forwards it to the correspondent node.

The present invention also relates to Mobile IPv6 technology. The following describes the basic principles of Mobile IPv6 in combination with Figure 3 and RFC 3775:

1. The home address of the mobile node will not change whether it is in the home network or a foreign network. When the mobile node is in the home network, the mobile node sends and receives data packets through the conventional IP routing mechanism;

2. After the mobile node moves to a foreign network, it obtains a care-of address. Data packets sent to this care-of address will be sent to the mobile node. A mobile node can have multiple care-of addresses at the same time;

3. After moving to a foreign network, the mobile node will send a binding update message to the home agent to register the primary care-of address it has obtained;

4. Communication nodes can be fixed or mobile. The mobile node can provide its current location information to its correspondent node through registration;

5. Before the mobile node sends a binding update message to the correspondent node, it first executes the Return Routability Procedure. The purpose of the Return Routability Procedure is to confirm that the home address of the mobile node and its care-of address are reachable.

The Return Routability Procedure contains 4 messages: Home Test Init, Care-of Test Init, Home Test, and Care-of Test. Among them, the Home Test Init and Care-of Test Init messages are sent from the mobile node to the correspondent node at the same time: the Care-of Test Init message is directly sent from the mobile node to the correspondent node, while the Home Test Init message is first sent through the reverse tunnel to the home network, and then from the home network to the correspondent node. After the communication node receives and processes the above two messages, it sends back the Home Test message and the Care-ofTest message to the mobile node respectively, and these two messages will return to the mobile node by the original route.

6. There are two ways for the mobile node to communicate with its correspondent node.

The first is the "two-way tunnel" approach. The data message sent by the communication node is routed to the home network, and the home agent intercepts the data message and sends the data message to the care-of address of the mobile node through the tunnel; while the data message sent by the mobile node is sent to the home network through the reverse tunnel. home network, and then sent from the home network to the correspondent node. In this way, the communication node does not need to know the current location information of the mobile node.

The second is the "route optimization" approach. This communication method allows the correspondent node to send data packets directly to the care-of address of the mobile node. The prerequisite is that the mobile node must register with the correspondent node so that the correspondent node knows the binding relationship between its home address and the care-of address.

7. When the communication node sends a data message to the mobile node, the destination address is the care-of address of the mobile node, and the data message carries the home address information of the mobile node. Similarly, when the mobile node sends a data message to the correspondent node, the source address is the care-of address, and the data message carries home address information. The purpose of carrying the home address is to ensure that the care-of address is transparent to applications above the network layer.

However, neither the Mobile IPv4 protocol nor the Mobile IPv6 protocol can be directly applied to the third case above. The main problem is: after the mobile node moves from the IPv6 network to the IPv4 network, it must register with the home agent in the IPv6 network, and this process is Cross-heterogeneous network; before the mobile node switches to the IPv4 network, its communication with the communication node is across the heterogeneous network, and after the handover, its communication with the communication node only needs to be carried out in the IPv4 network, which involves How to ensure the transparency of the mobile node's movement to the existing communication process as much as possible and how to improve the routing efficiency.

Contents of the invention

The purpose of the present invention is to address the above problems and provide a method for realizing communication between an IPv4 communication node and a mobile node across a heterogeneous network. Through this method, the original communication can still be maintained after the mobile node moves from the IPv6 network to the IPv4 network, and the transparency of the movement of the mobile node to the communication node is guaranteed. The purpose of the present invention is achieved like this:

1. Register with Home Agent

After the mobile node switches from the IPv6 network to the IPv4 network, it knows that it has entered the IPv4 network by receiving the proxy routing advertisement message in the IPv4 network, and then the mobile node obtains a care-of address in the IPv4 network where it is located. The mobile node should immediately register with the home agent in order to notify the home agent of its latest location information.

(1) Obtaining the address of the home agent

After the mobile node switches to the IPv4 network, it needs to know the IPv4 address of the home agent to register with the home agent. The present invention achieves the above object by setting a NAT-PT gateway with DNS-ALG between the IPv4 network and the IPv6 network. After the mobile node switches from the IPv6 network to the IPv4 network, it obtains a new care-of address. Before the mobile node registers the new care-of address with the home agent, it first sends out a domain name interpretation request about the home agent. As mentioned in the background technology section, the mobile node will finally obtain the address of the home agent in IPv4 format with the help of the NAT-PT gateway with DNS-ALG and the domain name server.

Application of the above method of the present invention also needs to meet the following conditions:

A. The mobile node supports both IPv4 and IPv6 protocols, so that it can freely switch between the IPv4 network and the IPv6 network;

B. Set up a NAT-PT gateway with DNS-ALG between the IPv4 network and the IPv6 network;

C. Configure a domain name for each home agent;

D. The mobile node remembers the domain name of the home agent;

(2) Format and processing of registration request message

In RFC3344 and RFC3775, the messages sent by the mobile node to register its care-of address with the home agent are different: RFC3344 describes the situation of an IPv4 network, which uses a registration request message (Registration RequestMessage); RFC3775 describes In the case of an IPv6 network, the Binding Update Message (Binding UpdateMessage) is used. In the present invention, the mobile node sends a registration request message to the home agent, and when the message passes through the NAT-PT gateway with the Mobile IP-ALG, the Mobile IP-ALG converts it into a binding update message and then sends it to the home agent. In the opposite direction, the home agent sends a binding confirmation message to the mobile node, and Mobile IP-ALG converts the message into a registration response message and then sends it to the mobile node.

A, because NAT-PT gateway generally only carries out the conversion of IP version to data message, and in the present invention, NAT-PT also will carry out the processing on the application layer to registration message and the data message that communication node sends, therefore, this Invented to set Mobile IP-ALG on NAT-PT gateway to complete these tasks. The functions of Mobile IP-ALG will be introduced in detail below.

B. In Mobile IPv4, the format of the registration request message is shown in Figure 4. In the present invention, since the home agent is in the IPv6 network, the home address and the care-of address in the registration request message finally received by the home agent should be in IPv6 format. The NAT-PT gateway can convert the care-of address in IPv4 format into IPv6 format (adding the NAT-PT gateway prefix in front), but the NAT-PT cannot obtain the home address of the mobile node in IPv6 format by conventional methods. Therefore, the present invention modifies the registration request message as follows: zero the original home address field, and carry the home address of the mobile node in IPv6 format in the extended part at the end of the message. The modified registration request message is shown in Fig. 5, wherein the extension part after the message contains the authentication data of the message. The registration request message is encapsulated with UDP, the destination port is 434, the source address is the care-of address in IPv4 format, and the destination address is the home agent address in IPv4 format obtained through DNS query.

C. When the above-mentioned registration request message passes through the NAT-PT gateway, the NAT-PT gateway intercepts the message according to the feature that the UDP destination port is 434, and sends the message to the Mobile IP-ALG for processing. Mobile IP-ALG first authenticates the message according to the authentication data in the message, and if the authentication passes, it converts it into a binding update message, in which the home address is obtained directly from the extension header of the above-mentioned modified registration request message . The source address of the binding update message is the care-of address in IPv6 format (obtained by NAT-PT adding a 96-bit NAT-PT gateway prefix to the source address of the original registration request message), and the destination address is the home agent address ( It is obtained by the NAT-PT gateway by querying the mapping table according to the destination address of the original registration request message).

D. After completing the processing described in step C, Mobile IP-ALG will also record the source address and destination address of the binding update message as a condition for later intercepting the binding confirmation message sent back by the home agent. In addition, Mobile IP-ALG will also remember the source port of the registration request message before conversion, so that it can be used later when processing the binding confirmation message.

E. After receiving the binding update message, the home agent first authenticates the message, and if the authentication passes, it further decides whether to accept the binding update. If the home agent agrees to accept the binding update, then create or update the binding cache about the mobile node, and send a binding confirmation message to the care-of address of the mobile node to indicate that the binding update has been accepted; otherwise, send a binding confirmation message to the care-of address of the mobile node Send a binding confirmation message to indicate rejection. Wherein, the above-mentioned care-of address is actually the source address of the binding update message, which is composed of the care-of address obtained by the mobile node in the IPv4 network plus a 96-bit NAT-PT gateway prefix. The source address of the binding confirmation message is the home agent address, and the destination address is the IPv6 form of the care-of address.

(3) Processing of binding confirmation message

Since the prefix of the destination address of the binding confirmation message is the prefix of the NAT-PT gateway, the message will pass through the NAT-PT gateway.

A. When the binding confirmation message passes through the NAT-PT gateway, the NAT-PT gateway checks its source address and destination address. If the NAT-PT gateway finds that these two addresses have been recorded before, it sends the message to Mobile IP-ALG on processing. The processing process is as follows: Mobile IP-ALG first authenticates the message, and if the authentication is passed, converts the binding confirmation message into a registration response message, and the Mobile IP-ALG will also carry the mobile node's ID in the extension part of the registration response message. IPv4 home address, this address will be used in subsequent communications. In RFC3344, the format of the registration response message is as shown in Figure 6, and the registration response message of the present invention is as shown in Figure 7, it is encapsulated with UDP, the source port is 434, and the destination port is the source port of the original registration request message (Mobile IP-ALG has been recorded). The source address of the message is the IPv4 address of the home agent, and the destination address is the IPv4 care-of address.

B. The Mobile IP-ALG creates or updates the binding cache between the IPv4 address of the mobile node and the IPv4 care-of address. This binding cache will be used later in the communication.

After C, mobile node receives above-mentioned registration response message, just can know the result of registration, and know the hometown address of own IPv4 form (this address is the address in the NAT-PT gateway address pool actually, communication node sends to mobile node Data packets always use this address as the destination address).

(4) After receiving the above-mentioned registration response message, the mobile node knows that its registration request has been allowed, and also knows its own home address in IPv4 format from the registration response message.

At this point, the registration of the care-of address is completed. It can be seen from the above description that the registration of the mobile node enables the home agent to obtain the latest information on the location of the mobile node, and also lets the NAT-PT gateway with Mobile IP-ALG know that the mobile node has switched from the IPv6 network to the IPv4 network, so that it can be in the IPv4 network In the subsequent communication, it plays a role similar to the home agent.

2. Communication between mobile nodes and communication nodes

After the mobile node completes the registration process, it can continue to communicate with the correspondent node. After the mobile node switches to the IPv4 network, its home agent is in the IPv6 network, while both the mobile node and the correspondent node are in the IPv4 network. Because the communication overhead between heterogeneous networks is relatively large, the principle of the present invention when designing the scheme is to allow the communication between the mobile node and the communication node without crossing the heterogeneous network (that is, without passing through the home agent in the IPv6 network), and simultaneously Keep the movement of the mobile node transparent to the two communicating parties, especially the communicating node.

(1) The communication node sends a data message to the mobile node

The format of the data message sent by the communication node to the mobile node is the same as that before the mobile node moves, the source address is its own address, and the destination address is the IPv4 home address of the mobile node (this address is actually the NAT-PT gateway address pool an address in ).

The above data message will be routed to the NAT-PT gateway. After the NAT-PT gateway intercepts the data message, Mobile IP-ALG searches its binding cache according to its destination address (ie, the home address in IPv4 format), and finds the corresponding The IPv4 care-of address. Then send the data message to the IPv4 care-of address of the mobile node through the tunnel. Specifically, Mobile IP-ALG adds a new IP header in front of the original data message, its source address is the IPv4 address of the NAT-PT gateway, and its destination address is the IPv4 care-of address.

After the mobile node receives the data message, it removes the outer IP header to obtain the data message sent to it by the communication node.

(2) The mobile node sends a data message to the correspondent node

The data message sent by the mobile node to the correspondent node is also in IPv4 format. The source address is the home address in IPv4 format, and the destination address is the address of the correspondent node. That is to say, the data message is sent directly from the network where the mobile node is currently located. to the communication node.

It can be seen from the above description that the NAT-PT gateway with DNS-ALG and Mobile IP-ALG plays an important role in the whole registration and communication process: firstly, it assists in completing the DNS query of the mobile node to the home agent address, Then it processes the registration request message and the binding confirmation message, and after the registration is completed, the NAT-PT gateway acts as a role similar to the home agent in MobileIPv4. By making full use of the existing Mobile IPv4 protocol and Mobile IPv6 protocol and setting DNS-ALG and Mobile IP-ALG on the NAT-PT gateway, the present invention not only realizes the communication after the mobile node is switched to a heterogeneous network, but also the mobile node and The data packets communicated by the communication nodes do not need to cross heterogeneous networks, which greatly improves the efficiency; in addition, the movement of the mobile node is completely transparent to the communication nodes: in the whole communication process, the communication nodes are actually going to the same address (that is, the IPv4 home address of the mobile node) to send and receive data packets.

Description of drawings

FIG. 1 is a schematic diagram of the basic principle of DNS query between heterogeneous networks;

Figure 2 is a schematic diagram of the basic principle of the Mobile IPv4 technology;

Figure 3 is a schematic diagram of the basic principles of the Mobile IPv6 technology;

Fig. 4 is a schematic diagram of a registration request message in Mobile IPv4 (RFC3344);

FIG. 5 is a schematic diagram of a modified registration request message;

Fig. 6 is a schematic diagram of a registration response message in Mobile IPv4 (RFC3344);

FIG. 7 is a schematic diagram of a modified registration response message;

Fig. 8 is a schematic diagram of the present invention.

Detailed ways

The present invention provides a kind of method that realizes IPv4 communication node and mobile node communication across heterogeneous network, its basic idea is: set Mobile IP-ALG and DNS-ALG on NAT-PT gateway, combine Mobile IPv4 agreement (RFC3344) and Mobile IPv6 protocol (RFC3775), propose a solution for the third situation above, so that the mobile node can successfully complete the registration with the home agent and maintain the original communication with the communication node after switching from the IPv6 network to the IPv4 network. And the movement of the mobile node is completely transparent to the communication node always in the IPv4 network.

An example of the present invention is given below, and the specific implementation manner of the present invention will be described in detail with reference to FIG. 8 .

1. Before the mobile node switches from the IPv6 network to the IPv4 network, the communication with the communication node in the IPv4 network has been established.

When the mobile node is in the IPv6 network, its communication with the communication node is across the heterogeneous network, and the data packets of different versions and formats are converted through the NAT-PT gateway during the communication process. When a mobile node moves from one network to another in an IPv6 network, it will obtain a new care-of address, and then the mobile node will register its newly obtained care-of address with its home agent and correspondent node respectively. When the mobile node registers with its home agent, the scheme in Mobile IPv6 (RFC3775) is adopted; after the mobile node completes the registration with the home agent, it initiates the process of registering with the correspondent node. For security and reliability considerations, before the mobile node formally sends a binding update message to the correspondent node, it needs to initiate the RRP (Return Routability Procedure) process, as described in the background technology section. Whether it is the RRP process or the subsequent binding update to the correspondent node, the work of the correspondent node is proxied by the NAT-PT gateway.

After the registration is completed, the communication process between the mobile node and the correspondent node is as follows: when the mobile node sends a data message to the correspondent node, its source address is the care-of address, and the destination address is the IPv6 address of the correspondent node (this address is determined by the IPv4 address of the correspondent node). The home address is composed of a 96-bit NAT-PT gateway prefix), and at the same time, a destination option extension header (Destination Option extension header) is inserted in the data message to carry the home address of the mobile node, and the data message arrives at the NAT-PT When the gateway is intercepted by the NAT-PT gateway and converted into a data message in IPv4 format, it is sent to the communication node. The source address of the converted data message is the IPv4 home address of the mobile node (actually the address in the NAT-PT gateway address pool). An IPv4 address), the destination address is the IPv4 address of the communication node. When the communication node sends a data message to the mobile node, the source address is the IPv4 address of the communication node, and the destination address is the IPv4 home address of the mobile node. When the data message passes through the NAT-PT gateway, it is converted into IPv6 format by the NAT-PT gateway. The source address of the converted data message is the IPv6 address of the communication node, and the destination address is the IPv6 care-of address. At the same time, after the conversion A Type 2 Routing Header (Type 2 Routing Header) is inserted into the data message to carry the IPv6 home address of the mobile node.

2. The mobile node learns that it has switched from the IPv6 network to the IPv4 network, and obtains a new care-of address in the IPv4 network.

Mobile agents in an IPv4 network will pseudo-periodically send agent advertisement messages in their network to indicate their existence. The mobile node can judge whether it has entered the IPv4 network from the IPv6 network according to the received agent advertisement message. The mobile node can also request the mobile agent to send an agent advertisement to itself by sending an agent request message to the mobile agent.

After the mobile node switches to the IPv4 network, it obtains a new care-of address. The care-of address can be obtained through DHCP or other methods.

The care-of address actually reflects the location information of the mobile node. After obtaining the new care-of address, the mobile node needs to tell the home agent its latest location information by registering with the home agent.

3. The mobile node queries the IPv4 address of the home agent through the domain name of the home agent.

After the mobile node obtains the care-of address, it needs to register with the home agent. Before the registration, the mobile node must know the IP address of the home agent to send a registration message. In the present invention, the mobile node obtains the IP address of the home agent through DNS query.

The mobile node sends a DNS query request to the DNS server in the IPv4 network to query the IP address of the home agent. If the DNS server in the IPv4 network cannot find relevant records, it will query the DNS server in the IPv6 network. The DNS server in the IPv6 network finds the relevant record of the above domain name, and returns a response message, which contains the IP address in IPv6 format corresponding to the above domain name. When the above response message passes through the NAT-PT gateway with DNS-ALG, the NAT-PT gateway will take out an IPv4 address from the address pool to map the IPv6 address, thereby obtaining the IPv6 address of the home agent. The modified reply message is returned to the mobile node. After receiving the above-mentioned response message, the mobile node knows the IPv4 address of the home agent.

4. The mobile node registers a new care-of address with its home agent through a registration request message.

In RFC3344 and RFC3775, the messages sent by the mobile node to register its care-of address with the home agent are different: RFC3344 describes the situation of an IPv4 network, which uses a registration request message (Registration RequestMessage); RFC3775 describes In the case of an IPv6 network, the Binding Update Message (Binding UpdateMessage) is used.

Since the mobile node has switched to the IPv4 network, the mobile node will send a registration request message to its home agent. In RFC3344, the format of the registration request message is shown in Figure 4, the source address is the care-of address, and the destination address is the home agent address. In the present invention, since the home agent is in the IPv6 network, the home address and the care-of address in the registration request message finally received by the home agent should be in IPv6 format. The NAT-PT gateway can convert the care-of address in IPv4 format into IPv6 format (add the NAT-PT gateway prefix in front), but the NAT-PT cannot obtain the IPv6 address of the mobile node in a conventional way. Therefore, the present invention modifies the registration request message: the original home address field is set to zero, and the IP address of the mobile node in IPv6 format is attached to the extension part at the end of the message. The modified registration request message is shown in FIG. 5 .

The registration request message is encapsulated by UDP, and the destination port is 434. According to this feature, the NAT-PT gateway intercepts the registration request message and sends it to the Mobile IP-ALG for processing. When processing the registration request message, Mobile IP-ALG first checks the reliability of the message according to the authentication information at the end of the registration request message (according to the processing method in RFC3344), if the authentication is passed, then Mobile IP-ALG will do the following two The first job is to convert the registration request message into a binding update message, and record relevant information as the basis for later intercepting the binding confirmation message sent back by the home agent. The process is described below:

(1) Mobile IP-ALG generates a binding update message according to the rules in RFC3775 according to the information provided by the registration request message intercepted by it, wherein the home address (IPv6 format) of the mobile node is obtained from the registration request message, The meanings of other fields are consistent with those specified in RFC3775. The source address of the binding update message is composed of the source address of the registration request message plus a 96-bit NAT-PT gateway prefix, which is actually the care-of address to be registered with the home agent; while the destination address of the binding update message is composed of The Mobile IP-ALG obtains it by querying its mapping relationship according to the destination address of the registration request message, which is actually the address of the home agent.

(2) In addition to processing the registration request message, the Mobile IP-ALG also needs to process the binding confirmation message sent back by the home agent later, so the Mobile IP-ALG needs some mechanism to intercept the binding confirmation message. The present invention handles like this: after finishing the described processing of step (1), Mobile IP-ALG writes down the source address and destination address of binding update message, and NAT-PT gateway checks the data sent to IPv4 network by IPv6 network By checking their source address and destination address, it can be determined whether the data packet is the binding confirmation message corresponding to the binding update message just now. In addition, after intercepting the binding confirmation message, Mobile IP-ALG needs to convert it into a registration response message, and the registration response message is also encapsulated with UDP, so Mobile IP-ALG also needs to remember the source port of the original registration request message.

5. The home agent sends a binding confirmation message to the mobile node.

After the home agent receives the above-mentioned binding update message, it first checks the reliability of the message according to the security authentication information in the message (processed according to the method of RFC3775), and if the authentication passes, then further processes the binding update request. If the home agent accepts the binding update, it will create or update its binding cache, that is, record the binding relationship between the home address of the mobile node, the care-of address, and the valid time of the binding, and send it to the care-of address of the mobile node. The binding confirmation message indicates that the binding update is successful; if the home agent rejects the request, it sends a binding confirmation message to the care-of address of the mobile node, indicating that the binding update fails and explains why. The source address of the binding confirmation message is the home agent address, and the destination address is the care-of address of the mobile node.

Since the destination address of the above binding confirmation message is actually the care-of address in IPv4 format plus a 96-bit NAT-PT gateway prefix, the message will pass through the NAT-PT gateway. The NAT-PT gateway checks the source address and the destination address of the message, and if they match the previous records (the positions of the source address and the destination address are exchanged), the message is sent to the MobileIP-ALG on the upper layer for further processing. Mobile IP-ALG first verifies the reliability of the message according to the authentication information of the binding confirmation message. If the authentication is passed, the following two things are further done: convert the binding confirmation message into a registration response message and send it to the mobile node's The care-of address, and the established binding cache. The specific instructions are as follows:

(1) Mobile IP-ALG generates a registration response message according to the information provided by the binding confirmation message, and carries the home address of the mobile node in IPv4 format in the extension part of the registration response message (this address is actually the NAT-PT gateway address An address in the pool, which the mobile node will use when communicating with the correspondent node). The message is encapsulated with UDP, its source port is 434, and its destination port is the source port recorded when processing the registration request message. The source address of the message is the IPv4 address of the home agent, which can be found from the mapping table; the destination address is the IPv4 care-of address.

(2) Mobile IP-ALG will also record the binding relationship between the mobile node's IPv4 home address and the IPv4 care-of address. This binding relationship will be used in subsequent communications, which will be described in detail later.

After the mobile node receives the above registration response message, it can know whether the registration has been accepted by the home agent, and also know the IPv4 form of its home address (that is, the destination address of the data message sent by the communication node). If the registration is accepted, the mobile node can continue to communicate with the correspondent node.

6. The communication node sends the data message to the mobile node.

When the communication node sends a data message to the mobile node, the data message passes through the NAT-PT gateway and is sent by the NAT-PT gateway to the care-of address of the mobile node through the tunnel.

The correspondent node does not actually know that the mobile node has moved, it simply sends a data message to the IPv4 home address of the mobile node (actually the address in the NAT-PT gateway address pool), that is, the correspondent node sends a message to the mobile node For the data message sent, the source address is its own IPv4 address, and the destination address is the IPv4 home address of the mobile node.

When the above data message passes through the NAT-PT gateway, it is intercepted by the NAT-PT gateway. The MobileIP-ALG on the NAT-PT gateway sends the message to the care-of address of the mobile node through the tunnel. Specifically, the Mobile IP-ALG adds a new IP header in front of the original data message, the source address of the new IP header is the NAT-PT gateway address, and the destination address is the care-of address of the mobile node.

At the care-of address of the mobile node, the mobile node decapsulates the received data message to obtain the data message inside.

7. The mobile node sends the data message to the correspondent node.

When the mobile node sends the data message to the correspondent node, it adopts the method of direct sending. Considering the transparency problem of the communication node side (that is, the movement of the mobile node should remain transparent to the communication node), the source address of the data message sent by the mobile node is its IPv4 home address, and the destination address is the address of the communication node.

As can be seen from the above specific implementation examples, the present invention is based on the existing Mobile IPv4 technology (RFC3344) and Mobile IP6 technology (RFC3775), by setting the DNS-ALG and Mobile IP-ALG between heterogeneous networks The NAT-PT gateway, and design the registration and communication process around the Mobile IP-ALG, so that the mobile node can still maintain communication with the communication node in the IPv4 network after switching from the IPv6 network to the IPv4 network. In addition, after the mobile node switches to the IPv4 network, the data packets sent between it and the correspondent node do not need to pass through the IPv6 network, and the movement of the mobile node is completely transparent to the correspondent node.

Claims (3)

1, a kind of mobile node method for communicating that realizes IPv4 communication node and cross-heterogeneous-network is characterized in that:

A, between IPv4 network and IPv6 network, be provided with the NAT-PT gateway of DNS-ALG and Mobile IP-ALG;

B, mobile node are supported IPv4 agreement and IPv6 agreement simultaneously, and mobile node is before switching to the IPv4 network from the IPv6 network, have set up and the communicating by letter of the communication node that is in the IPv4 network;

C, be domain name of each home agent configuration, mobile node is remembered the domain name of home agent; Mobile node moves behind the IPv4 network from the IPv6 network, and mobile node knows that self switches to the IPv4 network from the IPv6 network, and obtains a new Care-of Address at the IPv4 network, obtains the address of home agent IPv4 form by the inquiry of the domain name mode;

D, mobile node to the new Care-of Address of its home agent registration, the home address territory zero setting in the login request message, and carry the IPv6 home address of mobile node by login request message at the expansion of login request message;

Mobile IP-ALG on E, the NAT-PT gateway makes version conversion to register requirement, response message, and the data message of by the tunnel communication node being issued mobile node after registration is finished is sent to the Care-of Address of mobile node, thereby realizes the high usage route of data message.

2, the mobile node method for communicating of realization IPv4 communication node according to claim 1 and cross-heterogeneous-network is characterized in that " obtaining the address of home agent IPv4 form by the inquiry of the domain name mode " among the described step C specifically comprises:

(1) dns server of mobile node in the IPv4 network sends the DNS query requests about home agent;

(2) dns server in the IPv4 network can not find relative recording, then this query requests is forwarded to dns server in the IPv6 network, will be in the way through having the NAT-PT gateway of DNS-ALG;

(3) dns server in the IPv6 network is successfully resolved the domain name of the home agent of this mobile node, and sends a response message, and the IPv6 address of home agent is contained in this response message the inside;

When (4) above-mentioned response message was through the above-mentioned NAT-PT gateway that has a DNS-ALG, the NAT-PT gateway was found out the IPv6 address that an IPv4 address is used to shine upon above-mentioned home agent in its address pool, and above-mentioned response message is made suitable modification;

(5) mobile node is received above-mentioned response message through revising, thereby obtains the IPv4 address of home agent.

3, the mobile node method for communicating of realization IPv4 communication node according to claim 1 and cross-heterogeneous-network is characterized in that " mobile node is registered new Care-of Address by login request message to its home agent " specifically comprises among the described step D:

(1) mobile node sends login request message to home agent, and the NAT-PT gateway is that 434 these features are intercepted and captured this login request message according to login request message with UDP encapsulation and destination interface, and gives Mobile IP-ALG it and handle;

(2) Mobile IP-ALG sends to home agent after login request message is converted to binding update messages again;

(3) home agent is handled above-mentioned binding update messages and is sent the binding response message to the IPv6 of mobile node Care-of Address, whether the NAT-PT gateway is corresponding with previous binding update messages to determine this binding response message with destination address by the source address of checking the binding response message, if then give Mobile IP-ALG it and handle;

(4) this binding response message is converted to the Care-of Address that sends to mobile node behind the registration reply message again by Mobile IP-ALG.

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