%% You should probably cite draft-ietf-ipsecme-traffic-visibility instead of this I-D.
@techreport{grewal-ipsec-traffic-visibility-01,
    number =    {draft-grewal-ipsec-traffic-visibility-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-grewal-ipsec-traffic-visibility/01/},
    author =    {Ken Grewal},
    title =     {{XESP for Traffic Visibility}},
    pagetotal = 10,
    year =      2008,
    month =     jun,
    day =       23,
    abstract =  {This document describes an ESP encapsulation for IPsec, allowing intermediate devices to ascertain if ESP-NULL is being employed and hence inspect the IPsec packets for network monitoring and access control functions. Currently in the IPsec standard, there is no way to differentiate between ESP encryption and ESP NULL encryption by simply examining a packet.},
}