%% You should probably cite rfc7059 instead of this I-D.
@techreport{steffann-tunnels-04,
    number =    {draft-steffann-tunnels-04},
    type =      {Internet-Draft},
    institution =   {Internet Engineering Task Force},
    publisher = {Internet Engineering Task Force},
    note =      {Work in Progress},
    url =       {https://datatracker.ietf.org/doc/draft-steffann-tunnels/04/},
    author =    {S.J.M. Steffann and Iljitsch van Beijnum and Rick van Rein},
    title =     {{A Comparison of IPv6-over-IPv4 Tunnel Mechanisms}},
    pagetotal = 41,
    year =      2013,
    month =     may,
    day =       31,
    abstract =  {This document provides an overview of various ways to tunnel IPv6 packets over IPv4 networks. It covers mechanisms in current use, touches on several mechanisms that are now only of historic interest, and discusses some newer tunnel mechanisms that are not widely used at the time of publication. The goal of the document is helping people with an IPv6-in-IPv4 tunneling need to select the mechanisms that may apply to them.},
}