Session Initiation Protocol (SIP) Extensions for Blocking VoIP Spam Using PSTN Validation

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Last updated 2012-07-14 (latest revision 2012-01-11)
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This Internet-Draft is no longer active. A copy of the expired Internet-Draft can be found at


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.


Marc Petit-Huguenin (
Jonathan Rosenberg (
Cullen Jennings (

(Note: The e-mail addresses provided for the authors of this Internet-Draft may no longer be valid.)