A SIP Response Code for Unwanted Calls
RFC 8197

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Internet Engineering Task Force (IETF)                    H. Schulzrinne
Request for Comments: 8197                                           FCC
Category: Standards Track                                      July 2017
ISSN: 2070-1721

                 A SIP Response Code for Unwanted Calls

Abstract

   This document defines the 607 (Unwanted) SIP response code, allowing
   called parties to indicate that the call or message was unwanted.
   SIP entities may use this information to adjust how future calls from
   this calling party are handled for the called party or more broadly.

Status of This Memo

   This is an Internet Standards Track document.

   This document is a product of the Internet Engineering Task Force
   (IETF).  It represents the consensus of the IETF community.  It has
   received public review and has been approved for publication by the
   Internet Engineering Steering Group (IESG).  Further information on
   Internet Standards is available in Section 2 of RFC 7841.

   Information about the current status of this document, any errata,
   and how to provide feedback on it may be obtained at
   http://www.rfc-editor.org/info/rfc8197.

Copyright Notice

   Copyright (c) 2017 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Schulzrinne                  Standards Track                    [Page 1]
RFC 8197                     Status Unwanted                   July 2017

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Normative Language  . . . . . . . . . . . . . . . . . . . . .   3
   3.  Motivation  . . . . . . . . . . . . . . . . . . . . . . . . .   3
   4.  Behavior of SIP Entities  . . . . . . . . . . . . . . . . . .   3
   5.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   5
     5.1.  SIP Response Code . . . . . . . . . . . . . . . . . . . .   5
     5.2.  SIP Global Feature-Capability Indicator . . . . . . . . .   5
   6.  Security Considerations . . . . . . . . . . . . . . . . . . .   6
   7.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   7
     7.1.  Normative References  . . . . . . . . . . . . . . . . . .   7
     7.2.  Informative References  . . . . . . . . . . . . . . . . .   7
   Acknowledgements  . . . . . . . . . . . . . . . . . . . . . . . .   8
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .   8

1.  Introduction

   In many countries, an increasing number of calls are unwanted
   [RFC5039]: they might be fraudulent or illegal telemarketing or maybe
   the receiving party does not want to be disturbed by, say, surveys or
   solicitation by charities.  Carriers and other service providers may
   want to help their subscribers avoid receiving such calls, using a
   variety of global or user-specific filtering algorithms.  One input
   into such algorithms is user feedback.  User feedback may be offered
   through smartphone apps, APIs or within the context of a SIP-
   initiated call.  This document addresses feedback within the SIP
   call.  Here, the called party either rejects the SIP [RFC3261]
   request as unwanted or terminates the session with a BYE request
   after answering the call.  INVITE and MESSAGE requests are most
   likely to trigger such a response.

   To allow the called party to express that the call was unwanted, this
   document defines the 607 (Unwanted) response code.  The user agent
   (UA) of the called party, based on input from the called party or
   some UA-internal logic, uses this to indicate that this call is
   unwanted and that future attempts are likely to be similarly
   rejected.  While factors such as identity spoofing and call
   forwarding may make authoritative identification of the calling party
   difficult or impossible, the network can use such a rejection --
   possibly combined with a pattern of rejections by other callees and/
   or other information -- as input to a heuristic algorithm for
   determining future call treatment.  The heuristic processing and
   possible treatment of persistently unwanted calls are outside the
   scope of this document.

Schulzrinne                  Standards Track                    [Page 2]
RFC 8197                     Status Unwanted                   July 2017

   When this document refers to "caller identity", it uses "identity" in
   the same sense as [SIP-IDENTITY], i.e., to mean either a canonical