%% You should probably cite draft-ietf-intarea-gre-ipv6 instead of this I-D.
@techreport{pignataro-intarea-gre-ipv6-01,
    number =    {draft-pignataro-intarea-gre-ipv6-01},
    type =      {Internet-Draft},
    institution =   {Internet Engineering Task Force},
    publisher = {Internet Engineering Task Force},
    note =      {Work in Progress},
    url =       {https://datatracker.ietf.org/doc/draft-pignataro-intarea-gre-ipv6/01/},
    author =    {Carlos Pignataro and Ron Bonica and Suresh Krishnan},
    title =     {{IPv6 Support for Generic Routing Encapsulation (GRE)}},
    pagetotal = 5,
    year =      2014,
    month =     oct,
    day =       27,
    abstract =  {Generic Routing Encapsulation (GRE) can be used to carry any network layer protocol over any network layer protocol. GRE procedures are specified for IPv4, used as either the payload or delivery protocol. However, GRE procedures are not specified for IPv6, used as either the payload or delivery protocol. This document specifies GRE procedures for IPv6, used as either the payload or delivery protocol, and updates RFC 2784, the original GRE specification.},
}