E. Rescorla. <a href="http://www.ietf.org/rfc/rfc2631.txt"><cite> Diffie-Hellman Key Agreement Method.</cite></a>, IETF RFC 2631 Standards Track, 1999. URL: <a      href="http://www.ietf.org/rfc/rfc2631.txt">http://www.ietf.org/rfc/rfc2631.txt</a>