%% You should probably cite draft-ietf-trill-rbridge-multilevel instead of this I-D.
@techreport{perlman-trill-rbridge-multilevel-03,
    number =    {draft-perlman-trill-rbridge-multilevel-03},
    type =      {Internet-Draft},
    institution =   {Internet Engineering Task Force},
    publisher = {Internet Engineering Task Force},
    note =      {Work in Progress},
    url =       {https://datatracker.ietf.org/doc/draft-perlman-trill-rbridge-multilevel/03/},
    author =    {Radia Perlman and Donald E. Eastlake 3rd and Anoop Ghanwani and Hongjun Zhai},
    title =     {{RBridges: Multilevel TRILL}},
    pagetotal = 23,
    year =      2011,
    month =     oct,
    day =       31,
    abstract =  {This is an informational document describing issues and comparing advantages and disadvantages of various possible approaches to extending TRILL to use multiple levels of IS-IS.},
}