CN110691150A - SDN-based IPv4 and IPv6 interconnection method and system - Google Patents

Abstract

The invention discloses an SDN-based IPv4 and IPv6 interconnection method and system. The method steps are: when an IPv6/IPv4 client initiates access to an IPv4/IPv6 network using the domain name of the IPv4/IPv6 network, query and transfer through the SDN Request data and conversion control record query request, IPv4/IPv6 receives the converted record query request and finds that the domain name is the domain name in the network, and then replies with the record query response carrying the IPv4/IPv6 address, and transfers, translates and replies again through SDN , the IPv6/IPv4 client sends the first data packet with the received translated address as the destination address, transits through the SDN, sends it to the IPv4/IPv6 network after translation, and receives the reply data packet from the IPv4/IPv6 network, and then translates it into the fourth The data packet is sent to the IPv6/IPv4 client, and the IPv6/IPv4 client receives the fourth data packet. The invention can realize that only one routing table entry of the SDN controller of the SDN network is added on the basis of the traditional network to complete the interconnection of IPv4 and IPv6.

Description

An SDN-based IPv4 and IPv6 interconnection method and system

technical field

The invention relates to the field of network communication, in particular to an SDN-based IPv4 and IPv6 interconnection method and system.

Background technique

With the expansion of the network scale and the emergence of various new applications, more and more problems are exposed in the IPv4 network, and a huge cost is required to completely upgrade the current IPv4 network to the IPv6 network, so it will be a long time in the future. IPv4 and IPv6 will coexist within the time period. To ensure the continuity of network services, IPv6 transition technology must be introduced in the coexistence stage of IPv4 and IPv6. Each transition technology currently in use is specific to a specific application and is not universal. Therefore, in actual deployment, devices with corresponding functions are added to the network according to specific application requirements, which not only increases the complexity of network functions, but also leads to a waste of resources due to complex configuration.

Upgrading the current IPv4 network to IPv6 network not only requires the support of the equipment, but also needs to rewrite all the current network applications with the IPv6 protocol, which will cost incalculable. Therefore, upgrading from IPv4 to IPv6 is not a short period of time, but a gradual and long process, during which IPv4 and IPv6 will coexist. In the process of upgrading from IPv4 to IPv6, it is necessary to ensure that the original network services cannot be interrupted. Therefore, IPv6 transition technology must be introduced in the coexistence stage of IPv4 and IPv6. Consumption of network addresses; on the other hand, through the translation and conversion between IPv4 and IPv6, the interconnection between them is realized, thereby ensuring the continuity of current network services. At present, a variety of transition technologies have been developed for different needs, including dual-stack technology, tunnel technology, translation technology, etc. Each transition technology is only for a specific application requirement and is not universal. Therefore, in the In actual deployment, devices with corresponding functions need to be added to the network according to specific application requirements, which undoubtedly increases the complexity of the network. In addition, due to changes in network application requirements, network deployment needs to be changed according to changes in requirements, which not only increases the complexity of network deployment and configuration, but also causes waste of network resources. With the emergence of a new network architecture called Software Defined Networking (SDN, Software Defined Networking), these difficulties encountered in the traditional IPv6 transition technology can find a new solution.

SDN is a new type of network architecture proposed by the Clean Slat research group of Stanford University. Its originality is to decouple the network control and network forwarding in the traditional network into a control plane and a data plane. The control plane is open to the outside world. Control interfaces, network administrators can use these control interfaces to write specific network applications to control specific network requirements. The data plane only performs processing such as forwarding the data communication in the network according to the commands from the control plane. In an SDN network, the SDN controller as the control plane perceives the entire network, maintains the topology of the entire network, formulates network policies, and distributes policies, etc., while the SDN switch as the data plane completes packet forwarding according to the policies formulated and distributed by the controller. Wait. Once SDN came out, it has attracted wide attention from academia and business circles for its open, flexible and fine-grained network management and control methods. Or well-known IT industry giants such as Microsoft, Google, IBM, etc. have shown great importance to SDN, so SDN is likely to become the direction of the next generation of Internet architecture.

After the emergence of SDN, it has been concerned and applied in many aspects, such as network security, QoS guarantee, flow control, etc., but how to introduce the combined SDN technology in the traditional IPv6 transition technology, so as to solve the network complexity and business problems in the coexistence stage of IPv4 and IPv6. Sustainability, there is not much in-depth research. The research on IPv4 and IPv6 interconnection technology based on the SDN framework in this patent has certain theoretical and practical significance.

SUMMARY OF THE INVENTION

The purpose of the present invention is to overcome the shortcomings and deficiencies of the prior art, and to provide a method and system for interconnecting IPv4 and IPv6 based on SDN, which can realize an SDN controller that only adds an SDN network on the basis of a traditional network. Routing table entry to complete IPv4 and IPv6 interconnection.

The object of the present invention is achieved through the following technical solutions: a kind of SDN-based IPv4 and IPv6 interconnection method, comprising steps:

When the IPv6/IPv4 client initiates access to the IPv4/IPv6 network using the domain name of the IPv4/IPv6 server, it initiates a domain name first record query request to the SDN controller, and the resource type of the first record query request matches the DNS6/DNS4 resource type;

The domain name resolution management module is called through the SDN controller. If the domain name resolution management module cannot query the corresponding resource record, the first record query request is converted into a second record query request, and the second record query request type is the same as the DNS4/DNS6 resource type. match, send the second record query request to the domain name server DNS4/DNS6 in the IPv4/IPv6 network;

When DNS4/DNS6 receives the second record query request, it finds that the queried domain name is the domain name in its own network, generates the second record query response carrying the IPv4/IPv6 address through DNS4/DNS6, and replies the second record query response to SDN controller;

Through the SDN controller, the received second record query response is translated into a corresponding first record query response, and the IPv4/IPv6 address carried therein is translated into a corresponding IPv6/IPv4 address and returned to DNS6/DNS4;

After DNS6/DNS4 receives the reply from the SDN controller, it replies the received query response to the IPv6/IPv4 client;

Through the IPv6/IPv4 client, use the received IPv6/IPv4 address as the destination address to send the first data packet in IPv6/IPv4 format to the SDN (the first data packet reaches the SDN through the border router);

The network layer protocol conversion module is invoked through SDN to translate the first data packet in IPv6/IPv4 format into the first data packet in IPv4/IPv6 format, and send it to the IPv4/IPv6 network;

After receiving the first data packet, the IPv4/IPv6 network replies the second data packet in IPv4/IPv6 format to the IPv6/IPv4 client;

The network layer protocol conversion module is invoked through SDN to translate the second data packet in IPv4/IPv6 format into the second data packet in IPv6/IPv4 and send it to the IPv6/IPv4 network;

The IPv6/IPv4 client receives the second packet.

Preferably, the translation behavior follows the IP/ICMP translation algorithm defined in the RFC6145 standard; specifically, the IPv4 address is translated into the IPv6 address according to the algorithm defined in the RFC6052; the network layer protocol conversion module is invoked through SDN, and the IPv6 The translation of /IPv4 format packets into IPv4/IPv6 format packets conforms to the general NAPT mapping rule RFC3022.

Preferably, the step of translating an IPv6 address into a corresponding IPv4 address is:

Send the address application request to the address management and mapping module through the domain name resolution management module;

Select an available IPv4 address from the address pool through the address management and mapping module and return it to the domain name resolution management module, and establish an address binding relationship;

The domain name resolution management module synthesizes the received second record query response into a corresponding first query response according to the returned address and returns it to DNS4.

Preferably, the network layer protocol conversion module is invoked through SDN to translate the IPv6 format data packet into the IPv4 format data packet, and the specific steps for sending it to the IPv4 network are as follows:

The SDN switch receives the communication data packet from the IPv6 client to the IPv4 server, and finds that the destination address is an IPv4 mapped address. The SDN controller calls the address management and mapping module to check whether the source IPv6 address has a mapping relationship in the address translation table;

If not, select a free address from the IPv4 address pool to the source IPv6 address, convert it into an IPv4 address as a new source address, and establish a mapping relationship, and the destination address is converted to an IPv4 address according to the corresponding rules;

The IPv6 format data packet is translated into the IPv4 format data packet by the network layer protocol conversion module and sent to the IPv4 server.

Preferably, the network layer protocol conversion module is invoked through SDN to translate the IPv4 format data packet into the IPv6 format data packet, and the specific steps for sending it to the IPv6 network are as follows:

The SDN switch receives the communication IPv4 format data packet from the IPv4 client to the IPv6 server, and finds that the destination address is an IPv6 mapped address. The SDN controller calls the address management and mapping module to check whether the source IPv4 address has a mapping in the address translation table. relation;

If not, select a free address from the IPv6 address pool to give the source IPv4 address, the network layer protocol conversion module converts it into an IPv6 address as a new source address, and establishes a mapping relationship in the address conversion table, and the destination address is converted according to the corresponding rules to IPv6 address;

The IPv4 format data packet is translated into the IPv6 format data packet by the network layer protocol conversion module and sent to the IPv6 server.

An SDN-based IPv4 and IPv6 interconnection system, comprising an SDN controller, an SDN switch, a routing module and an interconnection module;

The routing module is installed in the SDN controller and is used for network routing of communication data packets between networks; it specifically includes a routing configuration submodule, a routing detection submodule and a routing management submodule;

The routing configuration submodule is used for the configuration of the border routing gateway device;

The routing detection sub-module is used for border routing gateway device detection;

The routing management submodule is used for the maintenance and management of information such as routing tables;

Described interconnection module is used for the acquisition of IP address, the management of IPv4 address and IPv6 address, mapping, conversion and the protocol translation of IPv4 format data packet and IPv6 format data packet; Described interconnection module specifically includes domain name resolution management submodule, network layer Protocol conversion sub-module, address management and mapping sub-module;

The domain name resolution management submodule is installed in the SDN controller and is used for proxy query and result conversion to help the client obtain the address embedded in the destination address;

The network layer protocol conversion submodule is installed in the SDN switch and is used for protocol translation and address conversion between the IPv4 data packet and the IPv6 data packet in the data communication process;

The address management and mapping sub-module is installed in the SDN controller and is used for dynamic management of IPv4 addresses and IPv6 addresses in the DNS resolution phase and establishment of the mapping relationship between IPv4 addresses and IPv6 addresses.

Preferably, the routing module, the domain name resolution management sub-module and the address management and mapping sub-module are installed and added to the SDN controller in the form of plug-ins.

Compared with the prior art, the present invention has the following advantages and beneficial effects:

1. The present invention only needs to add a routing table entry to the SDN controller of the SDN network on the DNS server, that is, through the address management and mapping sub-module installed in the SDN controller, to establish the IPv4 address and IPv6 address mapping relationship, the present invention Less changes to traditional networks.

2. The client of the IPv4 or IPv6 network in the present invention does not need to care whether the address corresponding to the domain name is IPv4 or IPv6, and only needs to input the domain name to access the service, so the present invention has strong transparency.

3. The present invention uses the standard control interface provided on the control plane to write the application program that realizes the interconnection function of IPv4 and IPv6, and then installs it in the form of a plug-in and adds it to the SDN controller and the switch, and some network applications are no longer required in the future. function, simply remove the relevant application module from the controller and switch. Therefore, the present invention is flexible and convenient.

4. The network layer protocol conversion sub-module of the present invention is installed and added to the SDN switch in the form of a plug-in, so the congestion of the SDN controller can be effectively avoided.

Description of drawings

1 is a schematic diagram of a SDN-based IPv4 and IPv6 interconnection system model according to Embodiment 3 of the present invention;

Fig. 2 is the process communication schematic diagram of IPv6 client of the present invention and IPv4 server;

3 is a flowchart of an IPv6 client accessing an IPv4 server according to Embodiment 1 of the present invention;

FIG. 4 is a flowchart of an IPv4 client accessing an IPv6 server according to Embodiment 2 of the present invention.

Detailed ways

In order to better understand the technical solutions of the present invention, the embodiments provided by the present invention are described in detail below with reference to the accompanying drawings, but the embodiments of the present invention are not limited thereto.

Example 1

As shown in FIG. 3 , this embodiment discloses a method of using a client in an IPv6 network as an initiating host to access a server in an IPv4 network (the steps of an IPv6 client accessing an IPv4 client are similar in principle, and will not be repeated here, Embodiment 2 Similarly), the domain name of the IPv6 client is "www.IPv6.com", and the domain name of the IPv4 server is "www.IPv4.com". The whole communication process is as follows:

Step S301: The IPv6 client initiates access to the IPv4 server by using the domain name www.IPv4.com of the IPv4 server. The IPv6 client first sends an RR type (resource type) record of "AAAA" to query the DNS6 domain name server, and queries the domain name www.IPv4.com .

Step S302: The domain name server DNS6 does not have a resource record corresponding to the domain name www.IPv4.com, so it initiates a record query request with an RR type of "AAAA" to the SDN controller.

Step S303: The SDN controller invokes the domain name resolution management module, and the record query sent by the domain name resolution management module does not have a corresponding resource record.

Step S304: The domain name resolution management module then converts the sent "AAAA" into an "A" record query request, and then sends it to the domain name server DNS4 in the IPv4 network.

Step S305: DNS4 receives the record query request from the SDN controller, finds that www.IPv4.com is a server in its own network, and replies the generated "A" record query response carrying the IPv4 address to the SDN controller.

Step S306: After receiving the reply from DNS4, the SDN controller translates the received "A" record query response into a corresponding "AAAA" query response, and translates the IPv4 address carried in it into a corresponding IPv6 address according to corresponding rules Return to DNS6 (the IPv4 address can be converted into an IPv6 address directly according to the existing rules, so it is not repeated here).

Step S307: After receiving the reply from the SDN controller, the DNS6 replies the received query response to the IPv6 client.

Step S308: After receiving the reply from DNS6, the IPv6 client sends the first data packet in IPv6 format to the IPv4 server using the IPv6 address in the reply message as the destination address.

Step S309: The SDN switch receives the first data packet in IPv6 format from the IPv6 client to the IPv4 server, and finds that the destination address is an IPv4 mapped address, and the SDN controller calls the address management and mapping module to query the source IPv6 in the address translation table Whether the address has a mapping relationship, if not, select a free address from the IPv4 address pool to the source IPv6 address, convert it into an IPv4 address as a new source address, and establish a mapping relationship. The destination address is converted to an IPv4 address according to the corresponding rules. Finally, the first data packet in IPv6 format is translated into the first data packet in IPv4 format by the network layer protocol conversion module and sent to the IPv4 server.

Step S310: After receiving the first data packet, the IPv4 server replies the second data packet in IPv4 format to the IPv6 client.

Step S311: After the SDN switch receives the second data packet in IPv4 format from the IPv4 server, it finds that its destination address is an IPv6 mapped address, so the SDN switch calls the network layer protocol conversion module, converts it into an IPv6 address according to the address mapping relationship, and uses The source IPv4 address queries its corresponding IPv6 address in the address translation table.

Step S312: Finally, the network layer protocol conversion module translates the second data packet in IPv4 format into the second data packet in IPv6 format, and sends the second data packet in IPv6 format after translation and conversion to the IPv6 client.

Example 2

As shown in FIG. 4 , this embodiment discloses a communication method for using a client in an IPv6 network as an initiating host to access a server in an IPv4 network, wherein the domain name of the IPv4 client is “www.IPv4.com”, and the domain name of the IPv4 server is “www.IPv4.com”. The domain name is "www.IPv6.com". The whole communication process is as follows:

Step S401: The IPv4 client initiates access to the IPv6 server by using the domain name www.IPv6.com of the IPv6 server, and the IPv4 client first sends an RR type "A" record to query the DNS4 domain name server to query the domain name www.IPv6.com.

Step S402: The domain name server DNS4 does not have a resource record corresponding to the domain name www.IPv6.com, so it initiates a query request for a record with an RR type of "A" to the SDN controller.

Step S403: The SDN controller invokes the domain name resolution management module, and the record query sent by the domain name resolution management module does not have a corresponding resource record.

Step S404: The domain name resolution management module then converts the sent "A" into an "AAAA" record query request, and then sends it to the domain name server DNS6 in the IPv6 network.

Step S405: DNS6 receives the record query request from the SDN controller, finds that www.IPv6.com is a server in its own network, and replies the generated "AAAA" record query response carrying the IPv6 address to the SDN controller.

Step S406: After the SDN controller receives the reply from DNS6, in order to map the IPv6 address to the IPv4 address space, the domain name resolution management module sends an address application request to the address management and mapping module, and the address management and mapping module selects an available address from the address pool. The IPv4 address returned is returned to the domain name resolution management module, and the address binding relationship is established. The domain name resolution management module synthesizes the received "AAAA" record query response according to the returned address and returns the corresponding "A" query response to DNS4.

Step S407: After receiving the reply from the SDN controller, the DNS4 replies the received query response to the IPv4 client.

Step S408: After receiving the reply from DNS4, the IPv4 client sends the first data packet in IPv4 format to the IPv6 server using the IPv4 address in the reply message as the destination address.

Step S409: The SDN switch receives the first data packet in IPv4 format from the IPv4 client to the IPv6 server, and finds that the destination address is an IPv6 mapped address, and the SDN controller invokes the address management and mapping module, because when the IPv6 address is converted to an IPv4 address , the long address cannot be uniquely translated into a short address, so check whether the source IPv4 address has a mapping relationship in the address translation table. If not, select a free address from the IPv6 address pool to the source IPv4 address, and the network layer protocol conversion module converts it into An IPv6 address is used as a new source address, and a mapping relationship is established in the address translation table, and the destination address is converted into an IPv6 address according to corresponding rules. Finally, the first data packet in IPv4 format is translated into the first data packet in IPv6 format by the network layer protocol conversion module and sent to the IPv6 server.

Step S410: After receiving the first data packet in IPv6 format, the IPv6 server replies the second data packet in IPv6 format to the IPv4 client.

Step S411: After the SDN switch receives the reply second data packet from the IPv6 server, it finds that its destination address is an IPv4 mapped address, so the SDN switch invokes the network layer protocol conversion module, converts it into an IPv4 address according to the mapping relationship of the address conversion table, and uses The source IPv6 address queries its corresponding IPv4 address in the address translation table.

Step S412: Finally, the network layer protocol conversion module translates the second data packet in IPv6 format into the second data packet in IPv4 format, and sends the second data packet in IPv4 format after translation and conversion to the IPv4 client.

Example 3

As shown in Figure 1, an SDN-based IPv4 and IPv6 interconnection system provided by this embodiment includes:

The routing configuration sub-module 101 realizes the configuration of the border routing gateway device; it is mainly that the network administrator dynamically configures the routing reachability information between the networks during the network operation process, and mainly configures the border routing gateway device that is directly connected to the edge switch. The network that can be reached, the network administrator adds or deletes the network that can be reached by the border routing gateway according to the change of the actual topology between the networks, and the routing reachability information between the configured networks only refers to the logical information at the network level;

The routing detection sub-module 102 realizes the detection of the border routing gateway device; when the network administrator configures the network reachability information of the border routing gateway, the controller will also actively detect the existence of the border routing gateway and its physical information in the SDN network, This work is completed by the border routing detection module, which constructs a probe message based on the IP address information of the border routing gateway specified by the administrator in the SDN network, and then broadcasts it on all edge switches. If there is such a border routing gateway device, it will Respond to the detection message, and the controller registers the device after receiving the response;

The routing management sub-module 103 implements maintenance and management of information such as routing tables; after the configuration and detection are completed by the configuration sub-module and the routing detection sub-module, the routing management sub-module adds the network reachability information to the routing forwarding table for maintenance and management, The whole system involves two types of IP addresses, IPv4 and IPv6. Two routing forwarding tables are established to manage the two address types separately. Then, according to the routing forwarding table, the cross-network data packets are queried to the corresponding egress border routing gateway device, and the control The controller selects a path in the SDN network to issue forwarding rules according to the switch to which the ingress gateway device is connected as the two endpoints, and the data packet reaches the destination network through this path.

The domain name resolution management sub-module 104 realizes proxy query and result conversion, and helps the client to obtain the address of the embedded destination address; can perform proxy query and result conversion to help the client obtain the address of the embedded destination address, and the resource server requested by the IPv6 user includes an IPv4 server and IPv6 server. When the user client accesses the IPv6 server, it will send a DNS "AAAA" record query request, and the DNS64 server will directly return the IPv6 address; when accessing the IPv4 server, it will also send a DNS "AAAA" record query request, but the DNS6 server has no record. ” records are converted into “A” records and forwarded to DNS4 for parsing, and then the specified prefix is added and converted into “AAAA” records and returned to the user client. The user client will receive IPv6 after initiating a DNS resolution request. Address, IPv6 address is calculated from the IPv4 address and the IPv6 prefix assigned to the NAT64 device, and the translation behavior follows the IP/ICMP translation algorithm defined in the RFC6145 standard. The resource servers requested by IPv4 users include IPv4 servers and IPv6 servers. When the user client accesses the IPv4 server, it will send a DNS "A" record query request, and the DNS64 server will directly return the IPv4 address; when accessing the IPv6 server, it will also send a DNS "A" record query request, but the DNS4 server has no record. ” record request is converted into “AAAA” record request and forwarded to DNS6 for parsing, and then request the network layer protocol conversion module to assign an available IPv4 address, establish a binding relationship in the address translation table, and convert the “AAAA” record It is returned to the user client in the form of an "A" record. The user client will receive an IPv4 address after initiating a DNS resolution request. The IPv4 address is dynamically allocated by NAT or NAPT, which conforms to the general NAPT mapping rule RFC3022.

The address management and mapping submodule 105 realizes the establishment of the dynamic management mapping relationship between IPv4 addresses and IPv6 addresses in the DNS resolution stage;

The network layer protocol conversion sub-module 106 realizes the protocol translation and address conversion between the IPv4 format data packet and the IPv6 format data packet in the data communication process; it is mainly responsible for the mutual conversion of the IPv4 and IPv6 format data packet headers, and the translation of TCP, UDP and IPv6 in the fourth layer. ICMP protocol, the IP address and port are changed during the conversion process. The translation behavior follows the IP/ICMP translation algorithm defined in the RFC6145 standard. The IPv4 address of the IPv4 server is translated to the IPv6 address according to the algorithm defined in RFC6052, and the mutual translation between the IPv6 address of the IPv6 host and the IPv4 address conforms to the general NAPT mapping rule RFC3022. If it is an ICMPv6/4 packet, translate the Type, Code and Param fields in the packet to obtain an ICMPv4/6 packet, translate the embedded packet header, and calculate the ICMPv4/6 packet checksum ; If it is a TCP or UDP packet, you only need to directly calculate the checksum of TCP and UDP.

The present invention utilizes the technical means of SDN to realize the interconnection function of IPv4 and IPv6 in the control plane and data plane in the form of software. This method does not need to change the existing IPv4 and IPv6 network equipment, which not only reduces the complexity of the network, but also reduces the configuration of the network. easy and convenient. When there is no need for IPv4 and IPv6 interconnection, it is only necessary to remove the IPv4 and IPv6 interconnection modules from the control plane and data plane, and the impact on the network is minimal.

The above-mentioned embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited by the above-mentioned embodiments, and any other changes, modifications, substitutions, combinations, The simplification should be equivalent replacement manners, which are all included in the protection scope of the present invention.

Claims (7)

1. An SDN-based IPv4 and IPv6 interconnection method is characterized by comprising the following steps:

when an IPv6/IPv4 client accesses an IPv4/IPv6 network by using the domain name of an IPv4/IPv6 server, a domain name first record query request is initiated to an SDN controller, and the resource type of the first record query request is matched with the resource type of DNS6/DNS 4;

calling a domain name resolution management module through an SDN controller, if the domain name resolution management module cannot query the corresponding resource record, converting the first record query request into a second record query request, wherein the type of the second record query request is matched with the DNS4/DNS6 resource type, and sending the second record query request to a domain name server DNS4/DNS6 in an IPv4/IPv6 network;

when the DNS4/DNS6 receives the second record query request, the queried domain name is found to be the domain name in the network of the DNS, a second record query response carrying an IPv4/IPv6 address is generated through the DNS4/DNS6, and the second record query response is replied to the SDN controller;

translating the received second record query response into a corresponding first record query response through an SDN controller, translating the carried IPv4/IPv6 address into a corresponding IPv6/IPv4 address, and returning the corresponding IPv6/IPv4 address to the DNS6/DNS 4;

after receiving the reply of the SDN controller, the DNS6/DNS4 replies the received query response to the IPv6/IPv4 client;

sending a first data packet in an IPv6/IPv4 format to the SDN by using the received IPv6/IPv4 address as a destination address through the IPv6/IPv4 client;

calling a network layer protocol conversion module through the SDN, translating the first data packet in the IPv6/IPv4 format into the first data packet in the IPv4/IPv6 format, and sending the first data packet to the IPv4/IPv6 network;

after the IPv4/IPv6 network receives the first data packet, replying the second data packet in the IPv4/IPv6 format to the IPv6/IPv4 client;

calling a network layer protocol conversion module through the SDN, translating the second data packet in the IPv4/IPv6 format into an IPv6/IPv4 second data packet, and sending the second data packet to the IPv6/IPv4 network;

the IPv6/IPv4 client receives the second data packet.

2. The SDN-based IPv4 and IPv6 interworking method of claim 1, wherein the translation behavior complies with an IP/ICMP translation algorithm defined in RFC6145 standard; specifically, the IPv4 address is translated into the IPv6 address according to the algorithm defined in RFC 6052; the SDN calls a network layer protocol conversion module, and the IPv6/IPv4 format data packets are translated into IPv4/IPv6 format data packets, so that the general NAPT mapping rule RFC3022 is met.

3. The SDN-based IPv4 and IPv6 interworking method of claim 1, wherein the step of translating an IPv6 address into a corresponding IPv4 address is:

sending an address application request to an address management and mapping module through a domain name resolution management module;

selecting an available IPv4 address from the address pool through the address management and mapping module, returning the address to the domain name resolution management module, and establishing an address binding relationship;

and synthesizing the received second record query response into a corresponding first query response according to the returned address by the domain name resolution management module, and returning the corresponding first query response to the DNS 4.

4. The SDN-based IPv4 and IPv6 interconnection method of claim 1, wherein a network layer protocol conversion module is invoked by the SDN to translate IPv6 format packets into IPv4 format packets, and the specific steps for sending to the IPv4 network are as follows:

the SDN controller calls an address management and mapping module to inquire whether a source IPv6 address has a mapping relation in an address translation table or not after receiving a communication data packet from an IPv6 client to an IPv4 server through the SDN switch and finding that the destination address is an IPv4 mapping address;

if not, selecting an idle address from the IPv4 address pool to the source IPv6 address, converting the idle address into an IPv4 address serving as a new source address, establishing a mapping relation, and converting the destination address into an IPv4 address according to a corresponding rule;

and translating the IPv6 format data packet into an IPv4 format data packet by a network layer protocol conversion module, and sending the IPv4 format data packet to the IPv4 server.

5. The SDN-based IPv4 and IPv6 interconnection method of claim 1, wherein a network layer protocol conversion module is invoked by the SDN to translate IPv4 format packets into IPv6 format packets, and the specific steps for sending to the IPv6 network are as follows:

receiving a communication IPv4 format data packet from an IPv4 client to an IPv6 server through an SDN switch, finding that a destination address is an IPv6 mapping address, calling an address management and mapping module by the SDN controller, and inquiring whether a source IPv4 address has a mapping relation in an address translation table;

if not, selecting a free address from the IPv6 address pool to the source IPv4 address, converting the free address into an IPv6 address by the network layer protocol conversion module to serve as a new source address, establishing a mapping relation in an address conversion table, and converting the destination address into an IPv6 address according to a corresponding rule;

and translating the IPv4 format data packet into an IPv6 format data packet by a network layer protocol conversion module, and sending the IPv6 format data packet to the IPv6 server.

6. An IPv4 and IPv6 interconnection system based on an SDN is characterized by comprising an SDN controller, an SDN switch, a routing module and an interconnection module;

the routing module is installed in the SDN controller and used for network routing of communication data packets between networks; the system specifically comprises a route configuration submodule, a route detection submodule and a route management submodule;

the routing configuration submodule is used for configuring the border routing gateway equipment;

the route detection submodule is used for detecting the border route gateway equipment;

the routing management submodule is used for maintaining and managing information such as a routing table and the like;

the interconnection module is used for acquiring IP addresses, managing, mapping and converting IPv4 addresses and IPv6 addresses and translating protocols of IPv4 format data packets and IPv6 format data packets; the interconnection module specifically comprises a domain name resolution management submodule, a network layer protocol conversion submodule and an address management and mapping submodule;

the domain name resolution management submodule is arranged in the SDN controller and used for agent query and result conversion and helping a client to obtain an address embedded with a destination address;

the network layer protocol conversion submodule is installed in an SDN switch and is used for protocol translation and address conversion between an IPv4 data packet and an IPv6 data packet in the data communication process;

the address management and mapping submodule is installed in the SDN controller and used for dynamically managing the IPv4 address and the IPv6 address in the DNS analysis stage and establishing the mapping relation between the IPv4 address and the IPv6 address.

7. The SDN-based IPv4 and IPv6 interconnection system of claim 6, wherein the routing module, domain name resolution management submodule and address management and mapping submodule are installed and added to an SDN controller in a plug-in manner.

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