Based On Nat-pt Gateway Conversion Alg Design And Implementation,

NAT-PT is a transition mechanism to be designed to allow direct communicationbetween IPv6-only networks and IPv4-only networks. The term NAT-PT stands forNetwork Address Translation and Protocol Translation. NAT refers to translation of anIPv4 address into an IPv6 address and vice-versa and PT stands for the translation ofthe IPv4 packet into a semantically equivalent IPv6 packet and vice-versa.In order to implement some feature, some of the application layer protocol willcontain the IP information and Port number of TCP/UDP in its payload, and forward itthrough network. Once these package go through the NAT-PT gateway, because thebasic function of NAT-PT is just translate the IP address of network layer andTCP/UDP layer of transport layer, if NAT-PT gateway don't do any process with theapplication layer payload of these package, it must be failed to complete thecommunication between two nodes. Therefore, NAT-PT must combine withApplication Layer Gateway to achieve its goal.In this subject, base the researching the basic function of NAT-PT, we will focuson the design and implement the ALG system for the most important application layerprotocol, it will be including DNS-ALG, FTP-ALG and SIP-ALG. The SIP-ALG is avery new feature and is an additional ALG for the NAT-PT gateway, regarding theRF2766. DNS is the one of the most important application layer protocol in internet,FTP is most popular file transfer protocol, and SIP will be wildly used in NetGeneration Network. All these three application protocols are needed to be supportedby ALG.In this thesis, firstly we will introduce the key protocol of IPv4-IPv6 translationgateway, which based the NAT-PT. Then we will research and analyses the principlefor each application layer protocol, and build the translation mode or algorithm foreach protocol to go through the NAT-PT gateway. After that it will describer the detaildesign of each ALG subsystem, and it will give some research in enhance andimprovement of ALG's performance. These two chapters are the most important chapter in this paper. Finally, it will design some test case to verify the function ofALG. In this thesis, author also introduces fast sort algorithm and fast search algorithmto the ALG system. This design and implement finally passed the testing and achievethe practicality goal.