%% You should probably cite rfc5202 instead of this I-D.
@techreport{ietf-hip-esp-06,
    number =    {draft-ietf-hip-esp-06},
    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-hip-esp/06/},
    author =    {Pekka Nikander and Robert Moskowitz and Petri Jokela},
    title =     {{Using the Encapsulating Security Payload (ESP) Transport Format with the Host Identity Protocol (HIP)}},
    pagetotal = 30,
    year =      2007,
    month =     jun,
    day =       12,
    abstract =  {This memo specifies an Encapsulated Security Payload (ESP) based mechanism for transmission of user data packets, to be used with the Host Identity Protocol (HIP). This memo defines an Experimental Protocol for the Internet community.},
}