%% You should probably cite rfc3311 instead of this I-D.
@techreport{ietf-sip-update-02,
    number =    {draft-ietf-sip-update-02},
    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-sip-update/02/},
    author =    {Jonathan Rosenberg},
    title =     {{The Session Initiation Protocol (SIP) UPDATE Method}},
    pagetotal = 13,
    year =      2002,
    month =     may,
    day =       1,
    abstract =  {This specification defines the new UPDATE method for the Session Initiation Protocol (SIP). UPDATE allows a client to update parameters of a session (such as the set of media streams and their codecs) but has no impact on the state of a dialog. In that sense, it is like a re-INVITE, but can be sent before the initial INVITE has completed. This makes it very useful for updating session parameters within early dialogs.},
}