A Session Initiation Protocol (SIP) Response Code for Rejected Calls
draft-ietf-sipcore-rejected-01

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Last updated 2018-11-25
Replaces draft-burger-sipcore-rejected
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SIPCORE                                                        E. Burger
Internet-Draft                                     Georgetown University
Intended status: Standards Track                       November 25, 2018
Expires: May 29, 2019

  A Session Initiation Protocol (SIP) Response Code for Rejected Calls
                     draft-ietf-sipcore-rejected-01

Abstract

   This document defines the 608 (Rejected) SIP response code.  This
   response code enables calling parties to learn their call was
   rejected by an intermediary and will not be answered.  As a 6xx code,
   the caller will be aware that future attempts to contact the same UAS
   will be likely to fail.  The present use case driving the need for
   the 608 response code is when the intermediary is an analytics
   engine.  In this case, the rejection is by a machine or other
   process.  This contrasts with the 607 (Unwanted) SIP response code,
   which a human at the target UAS indicated the call was not wanted.
   In some jurisdictions this distinction is important.  This document
   defines the use of the Call-Info header in 608 responses to enable
   rejected callers to contact entities that blocked their calls in
   error.

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
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   This Internet-Draft will expire on May 29, 2019.

Copyright Notice

   Copyright (c) 2018 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

Burger                    Expires May 29, 2019                  [Page 1]
Internet-Draft               Status Rejected               November 2018

   This document is subject to BCP 78 and the IETF Trust's Legal
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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   7
   3.  Protocol Operation  . . . . . . . . . . . . . . . . . . . . .   7
     3.1.  Intermediary Operation  . . . . . . . . . . . . . . . . .   7
     3.2.  UAC Operation . . . . . . . . . . . . . . . . . . . . . .   8
     3.3.  Legacy Interoperation . . . . . . . . . . . . . . . . . .   8
     3.4.  Announcement Requirements . . . . . . . . . . . . . . . .   9
   4.  Examples  . . . . . . . . . . . . . . . . . . . . . . . . . .  10
   5.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  15
     5.1.  SIP Response Code . . . . . . . . . . . . . . . . . . . .  15
     5.2.  SIP Feature-Capability Indicator  . . . . . . . . . . . .  15
   6.  Security Considerations . . . . . . . . . . . . . . . . . . .  15
   7.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  16
   8.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  17
     8.1.  Normative References  . . . . . . . . . . . . . . . . . .  17
     8.2.  Informative References  . . . . . . . . . . . . . . . . .  17
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .  19

1.  Introduction

   The IETF has been addressing numerous issues surrounding how to
   handle unwanted and, depending on the jurisdiction, illegal calls
   [RFC5039].  Technologies such as STIR [RFC7340] and SHAKEN [SHAKEN]
   address cryptographic signing and attestation, respectively, of
   signaling to ensure the integrity and authenticity of the asserted
   identity.

   This document describes a new SIP response code, 608, which allows
   calling parties to learn an intermediary rejected their call.  As
   described below, we need a distinct indicator to differentiate
   between a user rejection and an intermediary's rejection of a call.
   In some jurisdictions, calls, even if unwanted by the user, may not
   be blocked unless there is an explicit user request.  Moreover, users
   may misidentify the nature of a caller.  For example, a legitimate
   caller may call a user who finds the call to be unwanted.  However,
   instead of marking the call as unwanted, the user may mark the call
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