Research on IP Packet Expansion in a New-style VPN

A new scheme is developed for constructing secure VPN.In this scheme,security protocols are separated from operating system and integrated into the network equipment-Safe Ethernet Card.When a program makes use of network equi-pments,the protocols cannot be bypassed.The scheme can be used to provide security communication and prevent active attack.In the scheme,it's very important for the network usage efficiency in preferably solving IP packet expansion problem.IPComp,IP fragmentation and reassembly,the advantages and disadvantages of them are discussed for resolving IP Packet expansion.A new MTU reduced method is put forward in the VPN.The result shows that this method decreases the amount of IP packet fragment distinctly,and improves the usage rate of network bandwidth.