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

Document Type Active Internet-Draft (individual)
Author Russ Penar 
Last updated 2020-06-24
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SIPCORE                                                        R. Penar                                    
Internet-Draft                                                Microsoft
Intended Status: Standards Track                          June 24, 2020
Expires: January 01, 2021                                 

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


   This document defines the 120 (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. Scam), the call may go unanswered. Through a 1xx code, 
   the caller's network may become aware future attempts to contact the 
   same User Agent Server (UAS) will likely go unanswered. The initial 
   use case driving the need for a 120 response code is when the 
   intermediary is an analytics engine. Code 120 (Rated) contrasts with 
   607 (Unwanted) & 608 (Rejected) SIP response codes in which a human 
   at target UAS, or terminating network analytics, indicate the call 
   may not completed.  This document also defines use of a Call-Info 
   header field in 120 (Rated) 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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   Penar                  Expires January 1, 2020              [Page 1]

   Internet-Draft               Call Rating                   June 2020

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.  Forking
   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, 120, which allows calling parties to learn
   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. 
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   Internet-Draft               Call Rating                   June 2020

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