%% You should probably cite draft-ietf-l3vpn-virtual-subnet instead of this I-D.
@techreport{xu-l3vpn-virtual-subnet-01,
    number =    {draft-xu-l3vpn-virtual-subnet-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-xu-l3vpn-virtual-subnet/01/},
    author =    {Xiaohu Xu and Susan Hares and Fan Yongbing and Christian Jacquenet and Truman Boyes and Brendan Fee},
    title =     {{Virtual Subnet: A L3VPN-based Subnet Extension Solution}},
    pagetotal = 17,
    year =      2013,
    month =     sep,
    day =       9,
    abstract =  {This document describes a Layer3 Virtual Private Network (L3VPN)- based subnet extension solution referred to as Virtual Subnet, which can be used as a kind of Layer3 network virtualization overlay approach for data center interconnect.},
}