Design And Implementation Of NAT Module Software Based On CBN System

With the rapid development of network technology,the number of Internet users and mobile terminal users is expanding day by day,and the network IPv4 addresses are depleting.At the same time,although the use of IPv6 addresses can fundamentally solve the problem of network address exhaustion,but from a practical point of view,the evolution of IPv4 to IPv6 will be a vast and complex system engineering.How to use existing IPv4 addresses more efficiently has become an issue that network operators and telecom equipment providers urgently need to solve.As a mainstream solution to address the depletion of network addresses,Network Address Translation(NAT)technology which achieves a private network address to the public address 1 to 1 and N to 1 conversion,can greatly reduce the use of public address.Although the traditional NAT equipment can realize the function of network address translation,taking into account of the huge network traffic and the scale of conversion in the existing network,the integrated NAT equipment can not manage and maintain the entries efficiently and can not guarantee the conversion efficiency.Based on the pain points of traditional NAT equipment,this thesis uses the idea of switching control to realize the maintenance and management of NAT multi-instance,puts the NAT management function and NAT learning forwarding function on the control and forwarding plane respectively,and implements Carrier Grade NAT(CGN)System to meet the forwarding capacity and forwarding performance requirements.At the same time,as network equipment gradually evolves toward NFV,the virtualization of CGN system will also gradually become the major research direction of major telecom equipment providers.In view of this research direction,the CGN software system based on Fiberhome Operating System(FOS)software development platform designed in this thesis will also support running on the virtual machine.The article first introduces the network address transition technology,compares the advantages and disadvantages of each transition technology,and il ustrates the superiority of NAT technology in the transition technology,explains the principle of CGN system NAT,CGN key technologies and common deployment scenarios.Then a kind of NAT module is designed,which is based on the distributed architecture.The structure and implementation of this software module is introduced based on the design idea of separating the forwarding plane from the control plane.The FOS software development platform used in this thesis is introduced,as well as the system architecture,data structure and main functions and algorithms of designing CGN system based on the realization process of NAT module.Then based on the design of CGN system,this thesis introduces the implementation principle of NAT multi-instance structure and reliability,and implements the NAT components under single instance from three aspects: component creation,command line function and NAT mapping table.Finally,the result of test is introduced,including the function,specification and performance of NAT in the single instance scenario,which indicates that the single instance NAT component implemented in this thesis has initially reached the design requirements of the CGN system.