How to Implement smooth transition from IPv4 to IPv6

IPv6 is improved on the basis of IPv4. An important design goal of IPv6 is to be compatible with IPv4, because it is impossible to require immediate evolution of all nodes to the new Protocol version, if there is no transitional solution, any advanced protocol is of no practical significance. How to smoothly transition from IPv4 to IPv6 is the first problem to be solved in IPv6 development. At present, IETF has set up a dedicated working group to study the smooth transition from IPv4 to IPv6 and the efficient and seamless interconnection issues, and many solutions have been proposed. In order to achieve the four goals of gradual evolution, gradual deployment, address compatibility, and cost reduction in the transition from IPv4 to IPv6, IETF recommends evolution solutions such as dual-protocol stack, tunneling technology, and NAT. These evolution schemes have been demonstrated and practiced in commercial or experimental networks in Europe, Japan, and China. These evolution schemes need to be further combined with China's specific network practices and operation practices, and must be demonstrated, developed, and improved in large-scale commercial practices.

Dual-protocol stack Technology

The dual-protocol stack technology is the most direct way to make IPv6 nodes compatible with IPv4 nodes. The application objects are communication nodes such as hosts and routers. The IPv6 protocol stack is used when IPv6 nodes and IPv6 nodes of the Two-protocol stack are interconnected, and the IPv4 protocol stack is used when IPv4 nodes are interconnected with each other by means of 4over6. When an IPv6 node accesses an IPv4 node, it first requests a temporary IPv4 address from the dual-stack server and obtains the TEPTunnelEndPoint of the Gateway Router from the dual-stack server. On this basis, IPv6 nodes form a 4over6 IP package. The 4over6 packet is transmitted to the Gateway Router through the IPv6 network. The Gateway Router Removes Its IPv6 Header and sends the IPv4 packet to the IPv4 node through the IPv4 network. The Gateway Router must remember the ing between the IPv6 source address and the IPv4 temporary address so that the IP packet sent from the IPv4 node can be forwarded to the IPv6 node in the opposite direction. This method is fully compatible with IPv4 and IPv6. However, due to the need for dual-route infrastructure, the network complexity is increased and the problem of IP address depletion still cannot be solved.

Tunneling Technology

With the development of IPv6 networks, many local IPv6 networks have emerged, but these IPv6 networks need to be connected through IPv4 backbone networks. Tunnel technology is required to connect these isolated IPv6 islands. Using tunneling technology, you can connect a local IPv6 network through an Internet backbone network running the IPv4 protocol. Therefore, it is the most easy-to-use technology in the early stages of IPv4 to IPv6 transition.

The router encapsulates the IPv6 Data Group into IPv4. The source address and destination address of the IPv4 group are the IPv4 addresses at the tunnel entry and exit respectively. At the exit of the tunnel, route the IPv6 group to the destination site. Tunnel Technology only needs to be modified at the entrance and exit of the tunnel, and has no requirements on other parts, so it is very easy to implement. However, tunnel technology cannot directly communicate with IPv4 hosts and IPv6 hosts.

Network Address Translation/protocol conversion technology

The Network Address Translation/protocol conversion technology is combined with the SIIT protocol conversion, the traditional IPv4 dynamic address translation, and the appropriate application layer gateway, communication between a host with only IPv6 installed and a majority of applications with only IPv4 machines is achieved. It is a pure IPv6 node and an IPv4 node, all translation tasks, including addresses and protocols, are completed by network devices. The Gateway Router that supports the NAT-PT should have an IPv4 address pool for use during packet forwarding from IPv6 to an IPv4 domain. In addition, the Gateway Router supports DNS-ALG, play a role when IPv6 nodes access IPv4 nodes. The advantage of NAT-PT mode is that IPv4 and IPv6 nodes do not need to be upgraded. The disadvantage is that the implementation method of IPv4 nodes to access IPv6 nodes is complicated, protocol conversion and address translation are costly for network devices. They are generally used when other interconnection methods are unavailable.

The above technology relies heavily on the transition from an Internet Supporting IPv4 to an Internet Supporting IPv6. We expect IPv4 and IPv6 to be compatible with each other in this conversion process. Currently, the 6to4 mechanism is one of the more popular implementation methods. The key consideration of the 6to4 Technical Conversion policy planners is how to activate the connectivity between IPv6 routing domains when users have no reasonable choice for the basic IPv6 Transport Protocol provided by the ISP. When the local IPv6 service is missing, one of the solutions for providing connectivity is to encapsulate IPv6 groups into IPv4 groups. 6to4 is an automatic tunnel construction method. It requires only one unique IPv4 address in the world to allow the entire site to obtain IPv6 connections. Adding IPv6 and 6to4 support to IPv4NAT is an attractive transitional solution.

In short, the smooth transition from IPv4 to IPv6 is an inevitable step for people to achieve global Internet in the future. It can not be achieved overnight. The transition from IPv4 to IPv6 is a quite long transition period. During this transition period, IPv4 and IPv6 must coexist and solve the problem of mutual compatibility, so as to gradually achieve smooth evolution, in the end, all network nodes will run IPv6, giving full play to IPv6's advantages in address space, performance and security.