| The design idea of IPv4 brings up the present international internet, of which the core values are simplicity, flexibility and opening. There is no nowadays flourishing internet without IPv4. After more than twenty years' development and improvement, the internet based on IPv4 was accepted as such a protocol that mature in technique, easy to realize and excellent in dual-operation, which really made a great success. However, along with the rapid ascending demand of internet connection and the continual coming of new business such as voice, data, image, video and multi-media, the IP address has been dried up, at the same time the routing table sharply expanded, lacking supports to moving and network service quality and so on.Compared to IPv4, IPv6 has a much longer address. IPv6 has 128-bit address, which four times IPv4's. In a foreseeable long time, the IP space based on 128-bit address can provide all the possible network devices with a global-unique address. However, IPv6 is not only to expand the IP address space, but also improve the performance of the whole internet. The most important changes IPv6 makes are in the following five aspects: address expansion, header form simplicity, improvements on supports of header expansion and option, flow marker, ID inspection and security. IPv6's address expansion can make IP continuously increase regardless of the shortage of resource, which is useful to promote the routing efficiency; header form simplifying can lessen the route processing; meanwhile, improvements on supports of header expansion and option fit much more special demands while hardly influence the common data packets and the special ones to route; The method of marking flow provide a certain mechanism to process packets with higher efficiency especially in real time application; improvements in ID inspection and security make IPv6 much suitable for some business applications with special requirements in sensitive information and resources.Since there are too many devices and network structures to be upgraded, the deployment of IPv6 networks will take a certain long time. Before IPv6 network completely replaces IPv4 network, there will be part of network supporting Ipv6 network protocol stack. During the early period of transition, this portion of network can be looked as Ipv6 islands in Ipv4 ocean. There are three main ways to solve the problems during transition: dual protocol stack, tunnel configure and IPv4/IPv6 protocol translation conversion. Among them, tunnel configure is to use the established IPv4 devices serve for IPv6 mainframe, making the separated IPv6 "isolated islands" communicate beyond IPv4 network. In the original stage, the most applicable way is tunnel, that is: to transform IPv6 data into IPv4 ones at the entrance to tunnel then back to IPv6 data at the exit finally send to the destination. According to the way get to the tunnel destination, we may differ the tunnels from manual configure tunnels and auto configure tunnels."IPv6 Tunnels Test" this paper designed is to use manual tunnel configure realize communication between two IPv6-protocol-support mainframes through IPv4 tunnel on software layer. Based on two assumptions, this paper will separately discuss about how to realize communication based on IPv6 network protocol. In the first assumption, both sides of communication session support IPv6 protocol, and the subnet connecting them also support IPv6 protocol, then the software developed on IPv4 protocol will go on working well in the new environment after being made several changes. "IPv6 Network Transmission" will present this means. Well the second assumption takes that both sides support IPv6 protocol, but the subnet connecting them only support IPv4, then they have to turn to the IPv4 tunnel technique to realize communication. "Tunnel Safety Transmission" will introduce how to use manual configure method to make it. Furthermore, the major purpose of IPv4 is to simply server as the network communication protocol, so there are no security characteristics contained in it. Well IPv6 will easily realize the IP layer security features. This paper studies and realizes the AH option header, and applies RSA and MD5 algorithms to realize connectionless integrity, data source identification inspection, and encryption functions etc.In my design of "IPv6 Network Transmission", the end and the server will run respectively in two IPv6 support mainframes. The two ends will communicate through their IPv6 network under bottom Socket and realize asynchrony instant communication and document transfer under upper TCP protocol. In the design of "Tunnel Safety Transmission", both mainframes will use runnels to realize communication. Though there are many tunnels, manual configured tunnels is the simplest way to realize communication in IPv6 and also the basis of other tunnels. The paper will mainly discuss how to use this means to realize communication in communication software. Encapsulating the data Row socket manually, turn IPv6 data into Ipv4 dataflow through packaging.Through the research of this paper, I deeply understand Socket and am skilled in using Socket in both asynchrony communication and synchrony communication. Also I get a deep understanding on IM software. Along with the realization of the communication between an IPv6-protocoI-support end and an IPv6-protocol-support server through IPv4 tunnel, I have a throughout study in the data form of IPv4 and IPv6, the meaning of each field, the concept of IPv4 tunnel as well as the original socket programming. Meanwhile, through an encryption practice my knowledge of encrypt algorithm of RSA and MD5 deepens.Although tunnel means needs only to revise at the entrance and the exit of tunnel, it can not realize the communication between IPv4 server and IPv6 server. |
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