%% You should probably cite rfc2408 instead of this I-D.
@techreport{ietf-ipsec-isakmp-09,
    number =    {draft-ietf-ipsec-isakmp-09},
    type =      {Internet-Draft},
    institution =   {Internet Engineering Task Force},
    publisher = {Internet Engineering Task Force},
    note =      {Work in Progress},
    url =       {https://datatracker.ietf.org/doc/draft-ietf-ipsec-isakmp/09/},
    author =    {Jeff Turner and Mark J. Schertler and Mark S. Schneider and Douglas Maughan},
    title =     {{Internet Security Association and Key Management Protocol (ISAKMP)}},
    pagetotal = 86,
    year =      1998,
    month =     apr,
    day =       7,
    abstract =  {This memo describes a protocol utilizing security concepts necessary for establishing Security Associations (SA) and cryptographic keys in an Internet environment. {[}STANDARDS-TRACK{]}},
}