Abstract: Secure IP layer is one of the most important solutions.Secure mechanism at IP layer should at least include data integrity,data privacy,and antitraffic analysis.The traditional solutions for the protection of routing information all depend on the encryption of information at the data link layer or the physical layer.A new mechanism realized at the IP layer is presented in the paper.The new mechanism can prevent the communication from traffic analysis attack through preserving the privacy of routing information contained in the IP packets.It should play an important role in the pursuing for the security at the IP layer.