A Session Initiation Protocol (SIP) Response Code for Call Rating

Document Type Active Internet-Draft (individual)
Author Russ Penar 
Last updated 2020-06-02
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SIPCORE                                                        R. Penar                                    
Internet-Draft                                                Microsoft
Expires: January, 2021                                     June 02, 2020

      A Session Initiation Protocol (SIP) Response Code for Call Rating


   This document defines the 184 (Rated) Session Initiation Protocol
   (SIP) response code. This response code enables calling parties to
   learn an intermediary rated their call attempt.  Depending on 
   rating (e.g. Likely Scam), the call may be rejected or go unanswered. 
   Through a 1xx code, the caller?s network may become aware future 
   attempts to contact the same User Agent Server will likely go 
   unanswered. The initial use case driving the need for a 184 response 
   code is when the intermediary is an analytics engine. In this case,  
   the rating is constructed via machine or other process. This 
   contrasts with 607 (Unwanted) & 608 (Rejected) SIP response codes in
   which a human at target User Agent Server, or terminating network
   analytics,indicate the call may not completed.  This document also 
   defines use of a Call-Info header field in 184 responses to enable 
   negatively rated callers to contact entities that rated their calls 
   in error. This provides a remediation mechanism for legal callers 
   who find their calls going unanswered (not necessarily blocked).

Status of This Memo

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Copyright Notice

   Copyright (c) 2020 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
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Table of Contents

   1.  Introduction
   2.  Terminology
   3.  Protocol Operation
     3.1.  Intermediary Operation
     3.2.  JWS Construction
       3.2.1.  JOSE Header
       3.2.2.  JWT Payload
       3.2.3.  JWS Signature
     3.3.  UAC Operation
     3.4.  Legacy Interoperation
     3.5.  Announcement Requirements
   4.  Examples
     4.1.  Full Exchange
     4.2.  Web Site jCard
     4.3.  Multi-modal jCard
     4.4.  Legacy Interoperability
   5.  IANA Considerations
     5.1.  SIP Response Code
     5.2.  SIP Feature-Capability Indicator
     5.3.  JSON Web Token Claim
     5.4.  Call-Info Purpose
   6.  Security Considerations
   7.  References
     7.1.  Normative References
     7.2.  Informative References
   Authors' Addresses

1.  Introduction

   The IETF has been addressing numerous issues surrounding how to
   handle unwanted and, depending on the jurisdiction, illegal calls
   [RFC5039].  Secure Telephone Identity Revisited (STIR) [RFC7340] and
   Signature-based Handling of Asserted information using toKENs
   (SHAKEN) [SHAKEN] address the cryptographic signing and attestation,
   respectively, of signaling to ensure the integrity and authenticity
   of the asserted caller identity.

   This document describes a new Session Initiation Protocol (SIP)
   [RFC3261] response code, 184, which allows calling parties to learn
   that an intermediary rated their call.  As described below, we
   need a distinct indicator to signal how a call?s rating is being 
   presented to the called party. 

   For example, a legitimate caller may call a user who observes the 
   call is rated poorly, ?Likely Scam?. Thus, instead of answering the
   call, the called party simply does not answer the call. 

   The 184 response code addresses this need of remediating incorrectly
   rated calls. Specifically, this code informs the SIP User Agent
   Client (UAC) an intermediary rated the call and provides a
   redress mechanism allowing callers (or their operator) to contact 
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