ISDN User Part (ISUP) Cause Location Parameter for the SIP Reason Header Field
RFC 8606

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Internet Engineering Task Force (IETF)                         R. Jesske
Request for Comments: 8606                              Deutsche Telekom
Updates: 3326                                                  June 2019
Category: Standards Track
ISSN: 2070-1721

             ISDN User Part (ISUP) Cause Location Parameter
                    for the SIP Reason Header Field

Abstract

   The SIP Reason header field is defined to carry ISUP (ISDN User Part)
   cause values as well as SIP response codes.  Some services in SIP
   networks may need to know the ISUP location where the call was
   released in the PSTN (Public Switched Telephone Network) to correctly
   interpret the reason of release.  This document updates RFC 3326 by
   adding a location parameter for this purpose.

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
   https://www.rfc-editor.org/info/rfc8606.

Copyright Notice

   Copyright (c) 2019 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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   described in the Simplified BSD License.

Jesske                       Standards Track                    [Page 1]
RFC 8606             ISUP Release Location Parameter           June 2019

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   3
   3.  Rationale . . . . . . . . . . . . . . . . . . . . . . . . . .   3
   4.  Mechanism . . . . . . . . . . . . . . . . . . . . . . . . . .   3
   5.  Example . . . . . . . . . . . . . . . . . . . . . . . . . . .   4
   6.  Privacy Considerations  . . . . . . . . . . . . . . . . . . .   5
   7.  Security Considerations . . . . . . . . . . . . . . . . . . .   5
   8.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   6
     8.1.  Registration of the Location Parameter for the Reason
           Header Field  . . . . . . . . . . . . . . . . . . . . . .   6
   9.  Normative References  . . . . . . . . . . . . . . . . . . . .   6
   Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . .   7
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .   7

1.  Introduction

   Section 3.4 of [RFC3326] describes a SIP message flow for canceling
   an INVITE request when a REL (release) message is received from the
   ISUP side.  That document specifies the SIP Reason header field
   [RFC3326] that is used to indicate the reason of release.  The reason
   of release indicates why a SIP Dialog or a PSTN call, in cases where
   the call was interworked to the PSTN, was terminated.  The
   termination may be normal, based on a failure within an entity (e.g.
   temporary failure) or caused by other factors (e.g., congestion).
   The reason may be a SIP response or an ISUP release cause as
   specified within [Q.850].  [RFC6432] specifies that an ISUP [Q.850]
   cause code can be carried within a SIP response, but not the Q.850
   location information.  The [Q.850] location information identifies
   the part of the ISUP network where the call was released.

   This document adds a location value parameter to the reason-extension
   parameter defined in [RFC3326] so that the [Q.850] location value can
   be interworked from the PSTN.  The interworking from the PSTN needs
   only to include the location received by the interworking gateway.
   [Q.850] describes the definitions of the cause code values and the
   locations used in ISDN and DSS1 (Digital Subscriber Signalling System
   No. 1) environments.  The cause code is used for identifying the
   reason of release of a call, and the location identifies where the
   call was released.

Jesske                       Standards Track                    [Page 2]
RFC 8606             ISUP Release Location Parameter           June 2019

2.  Terminology

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and