Naturally, the Internet as an open network allows millions of users to interact each other. Furthermore, the giant network vulnerable to various malicious activities that potentially causes many (losses) for both resources and humanity. In order to reduce the potential attacking activities, Internet Engineering Task Force has standardized a network level security so-called IP Security. The key process behind the IP Security is a Security Association that is identified by Security Parameter Index. The initiation of Security Association performance depends on the encryption algorithm used. Hence, the performance of the algorithm candidate is an important consideration. This paper aims to evaluate some encryption algorithm to be used in IPv6 network. Results of the experiments shows that ECP 384 based on the elliptic curve algorithms outperforms than the traditional algorithm such as MODP 1024 and MODP 3072.