@techreport{petithuguenin-vipr-sip-antispam-03,
    number =    {draft-petithuguenin-vipr-sip-antispam-03},
    type =      {Internet-Draft},
    institution =   {Internet Engineering Task Force},
    publisher = {Internet Engineering Task Force},
    note =      {Work in Progress},
    url =       {https://datatracker.ietf.org/doc/draft-petithuguenin-vipr-sip-antispam/03/},
    author =    {Marc Petit-Huguenin and Jonathan Rosenberg and Cullen Fluffy Jennings},
    title =     {{Session Initiation Protocol (SIP) Extensions for Blocking VoIP Spam Using PSTN Validation}},
    pagetotal = 10,
    year =      2012,
    month =     jan,
    day =       11,
    abstract =  {Verification Involving PSTN Reachability (ViPR) is a new technique for inter-domain federation of SIP calls. ViPR makes use of the PSTN as an introduction mechanism to verify the correctness of mappings from phone numbers to domains. The PSTN introduction mechanism can also be used as a technique for blocking spam - a SIP caller is only authorized when its calling domain has previously called that same number over the PSTN. This document describes an extension to SIP which enables authorization of SIP calls based on a prior PSTN introduction.},
}