Completing the transition from IPv4 to IPv6 is not a problem

IPv6 is often compared to a small island, and IPv4 is compared to the ocean. In fact, we will also use different methods and technologies to complete the transition from IPv4 to IPv6. The real islands and oceans do not exist, because the network itself is connected. What's more, the two online versions are an evolutionary relationship.

1. Background and status quo of intercommunication technology

IPv6 is considered as one of the core standards of next-generation Internet protocols. However, a new protocol needs a process from being developed to widely used, especially for the Internet that IPv4 still supports. Before IPv6 became popular around the world, some networks always use the IPv6 protocol stack and want to communicate with the Internet normally. To achieve this goal, researchers must develop an IPv4/IPv6 interconnection technology to ensure a stable transition from IPv4 to IPv6. In addition, intercommunication technology should be "seamless" for common users ", efficient information transmission.

In order to conduct research on IPv4-to-IPv6 transition and efficient seamless interconnection, IETF has set up a dedicated working group, NGTRANS working group, to address this issue. At the same time, IETF has set up a 6-Bone test bed worldwide to study IPv6 features. A variety of transitional technologies and interconnection solutions have emerged. These technologies have their own characteristics and are used to solve communication problems in different transitional periods and environments.

In the early stage of transition, the Internet will be composed of an IPv4 running \ "Ocean \" and an IPv6 running \ "island. Over time, the IPv4 ocean will gradually become smaller, while IPv6 islands will become more and more, eventually completely replacing IPv4. In the early stages of transition, the problems to be solved can be divided into two categories: the first category is to solve the problem of communication between these IPv6 Island; the second type is to solve the problem of communication between the IPv6 Island and the IPv4 ocean.

Many solutions have been proposed to address these two types of problems, some of which are already quite mature and have formed RFC, some of which are just used as Internet draft and need to be further improved.

2. Three basic technologies for IPv4 to IPv6 transition

At present, there are three basic technologies to solve the transition problem: double protocol stack RFC 2893 obsolete RFC1933), tunnel technology (RFC 2893), NAT-PT (RFC 2766 ).

(1) Dual Stack)

The nodes using this technology run the IPv4 and IPv6 protocol stacks at the same time. This is the most direct way to ensure compatibility between IPv6 nodes and pure IPv4 nodes. It targets communication end nodes including hosts and routers ). This method is fully compatible with IPv4 and IPv6, but does not help with IP address depletion. Because dual-route infrastructure is required, this method increases the complexity of the network.

(2) Tunnel technology)

Tunnel technology provides a method to transmit IPv6 data using the existing IPv4 routing system: the IPv6 group is encapsulated in IPv4 datagram as unstructured data and transmitted by IPv4 networks. Tunnel can be divided into two categories based on the Creation Mode: (manual) configured tunnel and automatically configured tunnel. Tunnel Technology cleverly utilizes the existing IPv4 network. It provides a method to enable communication between IPv6 nodes during the transition period, but it cannot solve the problem of communication between IPv6 nodes and IPv4 nodes.

(3) NAT-PT

In addition to IPv4 address and IPv6 address translation, the translation gateway also includes protocols and translation. As an intermediate communication device, the translation gateway can convert the IP header address between IPv4 and IPv6 networks, and make corresponding semantic translation for the group according to different protocols, this allows transparent communication between pure IPv4 and pure IPv6 sites.