%% You should probably cite draft-ietf-6man-rfc1981bis instead of this I-D.
@techreport{hinden-6man-rfc1981bis-01,
    number =    {draft-hinden-6man-rfc1981bis-01},
    type =      {Internet-Draft},
    institution =   {Internet Engineering Task Force},
    publisher = {Internet Engineering Task Force},
    note =      {Work in Progress},
    url =       {https://datatracker.ietf.org/doc/draft-hinden-6man-rfc1981bis/01/},
    author =    {Jack McCann and Dr. Steve E. Deering and Jeffrey Mogul},
    title =     {{Path MTU Discovery for IP version 6}},
    pagetotal = 16,
    year =      2015,
    month =     dec,
    day =       1,
    abstract =  {This document describes Path MTU Discovery for IP version 6. It is largely derived from RFC 1191, which describes Path MTU Discovery for IP version 4. It obsoletes RFC1981.},
}