Research Of Anycast Technology

Anycast is one of the three communication modes in IPv6, which is a new communication mode. One host could communicate with any destination host in the same group through anycast; moreover the destination host is the nearest host. Because the technology of anycast is not so mature, there is a strict limitation on anycast address in IPv6, which is that anycast address could only be allocated to router, but not to host. In other words, anycast address couldn't be used as the source address when communicating. The grouper of IPv6 announced that this limitation would not be canceled until the researchers of IPv6 get more experiences and agree on them. Although this limitation restricts the development of anycast, the study on anycast still becomes more and more.The research on the technology of anycast at home and abroad mainly focuses on two aspects, which are the research on application layer and the one on network layer. The research on application layer mainly discusses how to apply the advantage of selecting the nearest host to communicate to other fields such as DNS, server mirror, VOD (Video on Demand), network game, etc. The research on network layer mainly focuses on anycast routing protocols and the communication modes. The task of anycast routing is to confirm a best route from source node to destination node for anycast group.The main contributions and research achievements of this thesis are listed as followings:1. Summarizing the research on anycast. Firstly, the author introduces the network architecture and basic theory of anycast and offers the instances of anycast on various fields on above basis. Secondly, the author analyzes the status quo of the research on anycast from six aspects, which include the application of anycast such as DNS, server mirror and VOD, the routing protocols, stateless service, group management protocols, security and extendability. In the thesis, the author not only introduces the new technologies and new architectures concerned by researchers at home and abroad in detail but also analyzes the urgent problems which is need to be solved now.2. Studying anycast on application layer in detail. Because that Anycast on application layer has the advantages of flexibility and extendibility and it can be implemented easily and can bring economic benefit quickly, it has become the focus of network research fields in recent years especially on network application. After analyzing the problems of route selection and load balance in the communication on application layer concerned by most experts, the author presents five methods on application layer. On this basis the author proposes an improved random selection algorithm that could reduce load fluctuating. Through large numbers of experiments, the author proves its rationality and validity.3. Studying anycast on network layer. In this thesis, the author studies the route selection, group management and related communication mode and proposes an improved anycast routing selection algorithm, which is called Minimum Cost Algorithm. Because data replication selection of data grid is similar to routing selection of anycast, the author improved it according to the characteristics of anycast. In this algorithm, Bi-Directional Load, transmission rate and time are all considered. With enough analysis of theory and simulation experiments, above algorithms are proved to be efficient, ro-bust and extendable, which can satisfy the need of anycast route selection.4. Studying the security of anycast. After analyzing current anycast security threats, the author offers several solutions to anycast security and proposes a new secure group management framework at the basis of other researchers'achievements. In this framework, all member operations such as the joining in and the dropping from the group must be permitted by the group manager and authenticated by the authentication server of the framework. PKI, which is a mature technology, is adopted in the server authentication. The communication between member and group manager and the one between member and authentication server adopt cryptograph transmission, and IPSec of IPv6 is also utilized to ensure the security communication. After analyzing and proving relevant theory, the author conducts the model test for this framework. It is proved that the mention framework can satisfy the requirements of anycast security.5. Discussing the anycast simulation in detail. For the reason of the limitation of experiment equipments and the restriction on anycast communication, most research on anycast stays at the phase of simulation through software to implement anycast communication currently. However, the function of anycast communication simulation is not included into current open source network simulators, which should be extended. In the thesis, the method on how to implement anycast communication based on NS2 is also discussed in detail.In the final part of the thesis, the author summarizes the whole research work and prospects the future task.