%% You should probably cite draft-ietf-sipcore-sip-websocket instead of this I-D.
@techreport{ibc-sipcore-sip-websocket-01,
    number =    {draft-ibc-sipcore-sip-websocket-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-ibc-sipcore-sip-websocket/01/},
    author =    {Inaki Baz Castillo and Jose Luis Millan and Victor Pascual},
    title =     {{The WebSocket Protocol as a Transport for the Session Initiation Protocol (SIP)}},
    pagetotal = 28,
    year =      ** No value found for 'doc.pub_date.year' **,
    month =     ** No value found for 'doc.pub_date' **,
    day =       ** No value found for 'doc.pub_date.day' **,
    abstract =  {This document specifies a WebSocket Sub-Protocol for a new transport in SIP (Session Initiation Protocol). The WebSocket protocol enables two-way realtime communication between clients and servers.},
}