%% You should probably cite draft-ietf-sipcore-digest-scheme instead of this I-D.
@techreport{yusef-sipcore-digest-scheme-06,
    number =    {draft-yusef-sipcore-digest-scheme-06},
    type =      {Internet-Draft},
    institution =   {Internet Engineering Task Force},
    publisher = {Internet Engineering Task Force},
    note =      {Work in Progress},
    url =       {https://datatracker.ietf.org/doc/draft-yusef-sipcore-digest-scheme/06/},
    author =    {Rifaat Shekh-Yusef},
    title =     {{The Session Initiation Protocol (SIP) Digest Authentication Scheme}},
    pagetotal = 8,
    year =      2017,
    month =     sep,
    day =       18,
    abstract =  {This document updates the Digest Access Authentication scheme used by the Session Initiation Protocol (SIP) to add support for SHA2 digest algorithms to replace the MD5 algorithm.},
}