Over-compatibility between IPv4 and IPv6

Now the network is very tight, and more users are joining the network, which leads to the lack of addresses. But there is already a solution, that is, the IPv6 protocol. However, most users still use IPv4, which leads to the IPv4 to IPv6 transition technology that we will discuss today.

IPv4 to IPv6 transition technology

Because of the size of the Internet and the large number of IPv4 users and devices in the current network, the transition from IPv4 to IPv6 cannot be achieved at one time. Moreover, the daily work of many enterprises and users is increasingly dependent on the Internet, and they cannot tolerate problems arising during protocol transition. Therefore, the transition from IPv4 to IPv6 must be a step-by-step process that can still communicate with other IPv4 users in the network while experiencing the benefits of IPv6. The smooth transition from IPv4 to IPv6 is also an important factor for the success of IPv6.

In fact, IPv6 has taken into account the transition from IPv4 to IPv6 during the design process, and provides some features to simplify the transition process. For example, an IPv6 address can use an IPv4-compatible address, which is automatically generated by an IPv4 address. You can also build a tunnel on an IPv4 network to connect to an IPv6 Island. At present, many mechanisms have been proposed for the IPv4-IPv6 transition problem, their implementation principle and application environment have their own focus, this part will give a systematic introduction to the basic strategy and mechanism of IPv4-IPv6 transition.

In the process of IPv4-IPv6 transition, the following principles and objectives must be followed:

◆ Ensure intercommunication between IPv4 and IPv6 hosts;

◆ Avoid dependency between devices during the update process, that is, update of a device does not depend on updates of other devices );

◆ For network managers and end users, the transition process is easy to understand and implement;

◆ Transition can be performed one by one;

◆ Users and operators can decide when and how to transition.

There are three main aspects: IP layer transition policies and technologies, Link Layer Support for IPv6, and IPv6 impact on the upper layer.

The industry has put forward many solutions for the evolution strategy of IPv4 to IPv6 technology. In particular, the IETF organization has set up a research group NGTRANS dedicated to studying this evolution, and has submitted various draft evolution strategies to make them standard. Looking at various Evolution Strategies, mainstream technologies can be divided into the following categories:

Dual-stack Policy

The most direct way to connect an IPv6 node with an IPv4 node is to add an IPv4 protocol stack to an IPv6 node. Nodes with dual-protocol stacks are called "IPv6/IPv4 nodes". These nodes can send and receive IPv4 groups or IPv6 groups. They can communicate with IPv4 nodes, or directly use IPv6 to communicate with IPv6 nodes. The dual-stack technology does not need to construct a tunnel, but the tunneling technology described later uses the dual-stack technology. IPv6/IPv4 nodes can be configured manually or automatically.

Tunneling Technology

In the early stages of IPv6 development, there must be many local pure IPv6 networks, which are isolated by IPv4 backbone networks. In order to connect these isolated IPv6 islands, we will adopt the tunnel technology to solve the problem. The existing IPv4 internet tunneling technology is used to connect many "IPv6 isolated islands" and gradually expand the IPv6 Implementation scope. This is the current plan of the International IPv6 test bed 6Bone.