%% You should probably cite draft-ietf-tsvwg-gre-in-udp-encap instead of this I-D.
@techreport{yong-tsvwg-gre-in-udp-encap-00,
    number =    {draft-yong-tsvwg-gre-in-udp-encap-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-yong-tsvwg-gre-in-udp-encap/00/},
    author =    {Edward Crabbe and Lucy Yong and Xiaohu Xu},
    title =     {{Generic UDP Encapsulation for IP Tunneling}},
    pagetotal = 10,
    year =      2013,
    month =     jun,
    day =       4,
    abstract =  {This document describes a method of encapsulating arbitrary protocols within UDP and GRE headers. In this encapsulation, the source UDP port may be used as an entropy field for purposes of load balancing while the payload protocol may be identified by the GRE Protocol Type.},
}