GENWiki

Premier IT Outsourcing and Support Services within the UK

User Tools

Site Tools


rfc:rfc8606

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
 Provisions Relating to IETF Documents
 (https://trustee.ietf.org/license-info) in effect on the date of
 publication of this document.  Please review these documents
 carefully, as they describe your rights and restrictions with respect
 to this document.  Code Components extracted from this document must
 include Simplified BSD License text as described in Section 4.e of
 the Trust Legal Provisions and are provided without warranty as
 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
 "OPTIONAL" in this document are to be interpreted as described in
 BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all
 capitals, as shown here.

3. Rationale

 The primary intent of the parameter defined in this specification is
 for use in IMS (IP Multimedia Subsystem) networks defined by 3GPP,
 but it is also open to be used by any other networks that include
 ISUP interworking gateways and use Q.850 reason codes.  The purpose
 of this parameter is to hold the location of the call release so that
 it can be transported from the originating PSTN entity to the SIP
 entity via a response or BYE message.  The ISDN location is defined
 in [Q.850].

4. Mechanism

 As defined by [RFC6432], any SIP Response message, with the exception
 of 100 (Trying), MAY contain a Reason header field with a Q.850
 [Q.850] cause code.
 This specification adds a parameter with the ISUP location value
 defined in [Q.850] to the Reason header field that identifies the
 location of the call release in ISUP.  The location is a 4-bit value
 that reflects the possible locations where an ISUP call is released.
 Some values are spare or reserved for national use.  The Augmented
 BNF (ABNF) [RFC5234] for this parameter is shown in Figure 1.

Jesske Standards Track [Page 3] RFC 8606 ISUP Release Location Parameter June 2019

   reason-extension    =/ isup-cause-location
   isup-cause-location =  "location" EQUAL isup-location-value
   isup-location-value =
      "U" /      ; for 0 0 0 0 user
      "LPN" /    ; for 0 0 0 1 private network serving the local user
      "LN" /     ; for 0 0 1 0 public network serving the local user
      "TN" /     ; for 0 0 1 1 transit network
      "RLN" /    ; for 0 1 0 0 public network serving the remote user
      "RPN" /    ; for 0 1 0 1 private network serving the remote user
      "LOC-6" /  ; for 0 1 1 0 spare
      "INTL" /   ; for 0 1 1 1 international network
      "LOC-8" /  ; for 1 0 0 0 spare
      "LOC-9" /  ; for 1 0 0 1 spare
      "BI" /     ; for 1 0 1 0 network beyond interworking point
      "LOC-11" / ; for 1 0 1 1 spare
      "LOC-12" / ; for 1 1 0 0 reserved for national use
      "LOC-13" / ; for 1 1 0 1 reserved for national use
      "LOC-14" / ; for 1 1 1 0 reserved for national use
      "LOC-15"   ; for 1 1 1 1 reserved for national use
                Figure 1: ABNF for isup-cause-location
 Note: These are the location values defined within [Q.850].  The
 'LOC-*' names are the wire codepoints for the values currently left
 as 'spare' or 'reserved' in [Q.850]; these will continue to be the
 wire codepoints in the case of future allocation or national usage of
 the such values.
 The UAC or UAS SHALL include the location parameter in a request or
 response when setting up the Reason header field with a [Q.850] cause
 when the ISUP [Q.850] location is available.
 The use of the location parameter is restricted to Q.850 cause
 values.  Other values MUST be ignored if present.

5. Example

 The following example shows a SIP 404 response message containing a
 Reason header field with a [Q.850] cause value and an isup-cause-
 location value.  The 404 Response will be sent when a gateway
 receives an ISUP release with a [Q.850] cause set to 1, meaning
 Unallocated (unassigned) number, i.e., the number is not known in the
 PSTN.

Jesske Standards Track [Page 4] RFC 8606 ISUP Release Location Parameter June 2019

       SIP/2.0 404 Not Found
       Via: SIP/2.0/TCP proxy.example.com:5060;branch=z9hG4bKx5st
       Via: SIP/2.0/TCP 192.0.2.3:5060;branch=z9hG4bK4321
       From: Alice <sips:alice@atlanta.example.com>;tag=1234567
       To: Bob <sips:bob@biloxi.example.com>;tag=765432
       Call-ID: 12345600@atlanta.example.com
       CSeq: 1 INVITE
       Reason: Q.850;cause=1;text="Unallocated (unassigned) number";
            location=LN
       Content-Length: 0
      Figure 2: Example of a Location in the Reason Header Field

6. Privacy Considerations

 While the addition of the location parameter provides an indicator of
 the entity that added the location in the signaling path, it provides
 little more exposure than the [Q.850] cause itself.  The ISUP
 location value itself will not reveal the identity of the originating
 or terminating party of the call.  It shows only the ISUP network
 location of the device that released the call.  The ISUP location
 does not show the physical location of the caller or callee.

7. Security Considerations

 This document doesn't change any of the security considerations
 described in [RFC3326].  The addition of the location parameter
 provides an indicator of the [Q.850] location where the call was
 released within the PSTN.  This information may be used for specific
 location-driven services but does not create any additional security
 constraints.  Because the [Q.850] location is very imprecise, the
 [Q.850] location value itself will not add any major security
 constraints.  The use of this parameter is not restricted to a
 specific architecture.
 [RFC3398] describes detailed security considerations due to
 interworking between ISUP and SIP.  Beyond these considerations, the
 addition of the location does not introduce new security concerns.
 The location shows the network part where the call was released.
 Knowing this does not increase the possibilities of extended fraud
 scenarios.

Jesske Standards Track [Page 5] RFC 8606 ISUP Release Location Parameter June 2019

8. IANA Considerations

8.1. Registration of the Location Parameter for the Reason Header Field

 IANA has registered a new SIP header parameter in the "Header Field
 Parameters and Parameter Values" subregistry of the "Session
 Initiation Protocol (SIP) Parameters" registry
 <https://www.iana.org/assignments/sip-parameters>, per the guidelines
 in [RFC3968]:
 Header Field:  Reason
 Parameter Name:  location
 Predefined Values:  Yes
 Reference:  RFC 8606

9. Normative References

 [Q.850]    ITU-T, "Usage of cause and location in the Digital
            Subscriber Signalling System No. 1 and the Signalling
            System No. 7 ISDN user part", Recommendation ITU-T Q.850,
            October 2018, <https://www.itu.int/rec/T-REC-Q.850>.
 [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
            Requirement Levels", BCP 14, RFC 2119,
            DOI 10.17487/RFC2119, March 1997,
            <https://www.rfc-editor.org/info/rfc2119>.
 [RFC3326]  Schulzrinne, H., Oran, D., and G. Camarillo, "The Reason
            Header Field for the Session Initiation Protocol (SIP)",
            RFC 3326, DOI 10.17487/RFC3326, December 2002,
            <https://www.rfc-editor.org/info/rfc3326>.
 [RFC3398]  Camarillo, G., Roach, A., Peterson, J., and L. Ong,
            "Integrated Services Digital Network (ISDN) User Part
            (ISUP) to Session Initiation Protocol (SIP) Mapping",
            RFC 3398, DOI 10.17487/RFC3398, December 2002,
            <https://www.rfc-editor.org/info/rfc3398>.
 [RFC3968]  Camarillo, G., "The Internet Assigned Number Authority
            (IANA) Header Field Parameter Registry for the Session
            Initiation Protocol (SIP)", BCP 98, RFC 3968,
            DOI 10.17487/RFC3968, December 2004,
            <https://www.rfc-editor.org/info/rfc3968>.

Jesske Standards Track [Page 6] RFC 8606 ISUP Release Location Parameter June 2019

 [RFC5234]  Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax
            Specifications: ABNF", STD 68, RFC 5234,
            DOI 10.17487/RFC5234, January 2008,
            <https://www.rfc-editor.org/info/rfc5234>.
 [RFC6432]  Jesske, R. and L. Liess, "Carrying Q.850 Codes in Reason
            Header Fields in SIP (Session Initiation Protocol)
            Responses", RFC 6432, DOI 10.17487/RFC6432, November 2011,
            <https://www.rfc-editor.org/info/rfc6432>.
 [RFC8174]  Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
            2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
            May 2017, <https://www.rfc-editor.org/info/rfc8174>.

Acknowledgments

 Thanks to Michael Kreipl, Thomas Belling, Marianne Mohali, Peter
 Daws, Paul Kyzivat, Dale Worley, Yehoshua Gev, and Keith Drage for
 the comments and review.

Author's Address

 Roland Jesske
 Deutsche Telekom
 Heinrich-Hertz Str, 3-7
 Darmstadt  64295
 Germany
 Email: r.jesske@telekom.de
 URI:   www.telekom.de

Jesske Standards Track [Page 7]

/data/webs/external/dokuwiki/data/pages/rfc/rfc8606.txt · Last modified: 2019/06/17 22:32 by 127.0.0.1

Donate Powered by PHP Valid HTML5 Valid CSS Driven by DokuWiki