%% You should probably cite draft-ietf-httpbis-cdn-loop instead of this I-D.
@techreport{cdn-loop-prevention-00,
    number =    {draft-cdn-loop-prevention-00},
    type =      {Internet-Draft},
    institution =   {Internet Engineering Task Force},
    publisher = {Internet Engineering Task Force},
    note =      {Work in Progress},
    url =       {https://datatracker.ietf.org/doc/draft-cdn-loop-prevention/00/},
    author =    {Stephen Ludin and Mark Nottingham and Nick Sullivan},
    title =     {{CDN Loop Prevention}},
    pagetotal = 5,
    year =      2018,
    month =     jun,
    day =       26,
    abstract =  {This specification defines the CDN-Loop request header field for HTTP.},
}