%% You should probably cite rfc3948 instead of this I-D.
@techreport{ietf-ipsec-udp-encaps-09,
    number =    {draft-ietf-ipsec-udp-encaps-09},
    type =      {Internet-Draft},
    institution =   {Internet Engineering Task Force},
    publisher = {Internet Engineering Task Force},
    note =      {Work in Progress},
    url =       {https://datatracker.ietf.org/doc/draft-ietf-ipsec-udp-encaps/09/},
    author =    {Victor Volpe and Markus Stenberg and Brian Swander and Larry DiBurro and Ari Huttunen},
    title =     {{UDP Encapsulation of IPsec ESP Packets}},
    pagetotal = 15,
    year =      2004,
    month =     may,
    day =       5,
    abstract =  {This protocol specification defines methods to encapsulate and decapsulate IP Encapsulating Security Payload (ESP) packets inside UDP packets for traversing Network Address Translators. ESP encapsulation, as defined in this document, can be used in both IPv4 and IPv6 scenarios. Whenever negotiated, encapsulation is used with Internet Key Exchange (IKE). {[}STANDARDS-TRACK{]}},
}