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| A scalable and efficient IPv4 address sharing approach in IPv6 transition scenarios |
| Guo-liang Han, Cong-xiao Bao, Xing Li |
| CERNET Center, Tsinghua University, Beijing 100084, China |
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Abstract IPv6 has been an inevitable trend with the depletion of the global IPv4 address space. However, new IPv6 users still need public IPv4 addresses to access global IPv4 users/resources, making it important for providers to share scarce global IPv4 addresses effectively. There are two categories of solutions to the problem, carrier-grade NAT (CGN) and ‘A+P’ (each customer sharing the same IPv4 address is assigned an excluded port range). However, both of them have limitations. Specifically, CGN solutions are not scalable and can bring much complexity in managing customers in large-scale deployments, while A+P solutions are not flexible enough to meet dynamic port requirements. In this paper, we propose a hybrid mechanism to improve current solutions and have deployed it in the Tsinghua University Campus Network. The real traffic data shows that our mechanism can utilize limited IPv4 addresses efficiently without degrading the performance of applications on end hosts. Based on the enhanced mechanism, we propose a method to help service providers make address plans based on their own traffic patterns and actual requirements.
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Received: 14 January 2015
Published: 04 August 2015
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IPv6过渡场景中的可扩展高效IPv4地址共享机制研究
目的：在IPv6过渡方案中，研究同时具有良好可扩展性、灵活性和IPv4地址共享效率的IPv4地址共享机制，以促进IPv6的过渡进程。
创新点：在已有IPv6过渡机制基础上，提出一种混合的数据通路动态切换机制，可以兼顾已有的无状态机制和有状态机制的优点，从而实现良好的可扩展性、灵活性、安全性和高效的IPv4地址共享。该机制尤其适用于IPv4地址匮乏但用户数量很多的网络，可以在保证用户体验的同时充分促进该网络向IPv6的过渡。在此机制基础上，提出根据实际情况进行灵活的地址规划的方法。
方法：首先，针对当前的IPv4地址共享机制的不足，提出并设计混合的数据通路动态切换机制，其中动态切换的过程由用户侧网关完成。然后，设计该机制的组成模块，并分别讨论其实现算法和细节。接下来，将整个系统实现并部署在连接至IPv6骨干网CERNET2的清华大学校园网中，通过实际流量数据分析该机制对有状态通路和无状态通路上流量和端口消耗的影响，验证该机制的可行性和有效性。最后，在此机制基础上，提出根据实际情况进行灵活的地址规划的方法。
结论：本文所提方法可以有效地使用有限的IPv4地址而不降低终端性能。实验结果（图6-8）验证了所提方法的有效性。该方法尤其适用于具有大量用户且希望使用有限IPv4地址的网络。
关键词：
IPv6过渡,
CGN,
A+P,
地址共享,
地址规划
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