A SIP Response Code (497) for Call Transfer Failure
draft-khatri-sipcore-call-transfer-fail-response-00

Document Type Active Internet-Draft (individual)
Authors Shrawan Khatri  , Vikram Singh  , Marcelo Pazos  , Cherng-Shung Hsu  , Yong Xie 
Last updated 2021-03-11
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Network Working Group                           Shrawan Kumar Khatri
Internet-Draft                                          Vikram Singh
                                                       Marcelo Pazos
                                                    Cherng-Shung Hsu
                                                            Yong Xie
Intended status: Standard Track                Qualcomm Incorporated
Expires: September 2021                               March 11, 2021

          A SIP Response Code (497) for Call Transfer Failure
        draft-khatri-sipcore-call-transfer-fail-response-00.txt

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Abstract

Khatri                Expires September 11, 2021            [Page 1]
Internet-Draft          Call Transfer Failure             March 2021

   This document defines the 497 (Call Transfer Failure) SIP
   response code, allowing Call Pull and Call Push parties to
   indicate that the operation was rejected. Optional warning codes
   are defined to carry granular information. SIP entities may use
   this information to adjust how subsequent calls can be handled
   intelligently.

Table of Contents

   1. Introduction................................................. 2
   2. Normative Language........................................... 3
   3. Motivation................................................... 3
   4. Theory of Operation.......................................... 4
   5. IANA Considerations.......................................... 6
      5.1. SIP Response Code....................................... 6
      5.2. Warning codes........................................... 7
      5.3. SIP Global Feature-Capability Indicator................. 8
   6. Security Considerations...................................... 8
   7. References................................................... 8
      7.1. Normative References.................................... 8
   8. Acknowledgments.............................................. 9

1. Introduction

  Packet switch calls for voice, video and text applications using
  IP Multimedia Subsystems (IMS) are anchored in the IMS core
  network. The signaling plane and media plane of IMS calls
  established on one device can be pushed ("Call Push") to another
  device. Similarly, IMS calls established on one device can be
  pulled ("Call Pull") by another device using SIP signaling.

  The call status during the SIP transaction can be conveyed through
  SIP response codes. RFC 3261 has defined many SIP response codes.
  The IMS core network MAY define a policy to allow or reject the
  Call Pull or Call Push operation. There are numerous reasons why
  the Call Pull or Call Push operation can fail. In case of call
  transfer failure due to policy defined by the IMS core network,
  the IMS core network MAY want to convey the failure to the user
  agent (UA) through a response code. Based on the response code,
  the UA MAY determine whether and how to establish a subsequent
  call.

Khatri                Expires September 11, 2021            [Page 2]
Internet-Draft          Call Transfer Failure             March 2021

  The existing response codes in RFC 3261 are not sufficient to
  convey the information about the call transfer failure to the UA.
  Overloading an existing response code could lead to unnecessary
  subsequent signaling which could burden the IMS core network. To
  avoid possible signaling overload in the IMS core network and to
  accurately convey the call transfer failure to the UA, a new
  response code along with associated optional warning codes to be
  included in a Warning header field are proposed in this RFC.

2. Normative Language
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