Sipcore R. Jesske Internet-Draft Deutsche Telekom Updates: RFC3326 (if approved) February 12, 2018 Intended status: Standards Track Expires: August 16, 2018 ISUP Cause Location Parameter for the SIP Reason Header Field draft-ietf-sipcore-reason-q850-loc-03.txt Abstract The SIP Reason header field is defined for carrying ISDN User Part (ISUP) 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 network to correctly interpret the reason of release. Status of This Memo This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet- Drafts is at https://datatracker.ietf.org/drafts/current/. 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Code Components extracted from this document must include Simplified BSD License text as described in Section 4.e of Jesske Expires August 16, 2018 [Page 1] Internet-Draft ISUP Release Location Parameter February 2018 the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 2 3. Rationale . . . . . . . . . . . . . . . . . . . . . . . . . . 2 4. Mechanism . . . . . . . . . . . . . . . . . . . . . . . . . . 3 5. Example . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 6. Privacy Considerations . . . . . . . . . . . . . . . . . . . 4 7. Security Considerations . . . . . . . . . . . . . . . . . . . 4 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5 8.1. Registration of location Parameter for Reason header field . . . . . . . . . . . . . . . . . . . . . . . . . . 5 9. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 5 10. Normative References . . . . . . . . . . . . . . . . . . . . 5 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 6 1. Introduction The SIP Reason header field specification [RFC3326] describes a SIP header field that is used to indicate that a SIP request is carrying the reason of release. It may be an SIP response or ISUP release cause as specified within [Q.850]. [RFC3326] does specify that a ISUP [Q.850] cause code can be carried within a SIP response. 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 in [RFC3326] so that the [Q.850] location value can be interworked from the PSTN. The interworking from PTSN needs only to include the location received by the interworking gateway. 2. Terminology The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in [RFC2119]. 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 also open to be used by any other network. The purpose of this parameter is to transport the location of call release from the originating PSTN entity to the SIP entity receiving the response or Jesske Expires August 16, 2018 [Page 2] Internet-Draft ISUP Release Location Parameter February 2018 BYE message containing the location of the call release. The ISDN location is defined in [Q.850]. 4. Mechanism As defined by [RFC3326] a Reason header field MAY appear in any request in a dialog, in any CANCEL request and in any response whose status code explicitly allows the presence of this header field. The syntax of the header field follows the standard SIP parameter syntax. The mechanism employed adds a parameter with the ISUP location value defined in [Q.850] to the Reason header field that identifies the [Q.850] location of the call release in ISUP as defined in [Q.850] . The location is a 4 bit value which 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. reason-extension =/ isup-cause-location isup-cause-location = "location" EQUAL string The following values shall be used as location: 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: isup-cause-location Note: These are the values defined within [Q.850] as location. Thus other values are not within the scope of this document. Depending on the direction the UAC or UAS shall include the location parameter when setting up the Reason header field with a [Q.850] cause. This approach is only valid in cases when the ISUP [Q.850] location is available. Jesske Expires August 16, 2018 [Page 3] Internet-Draft ISUP Release Location Parameter February 2018 The use of the location parameter is restricted to Q850 cause values in other cases the location, if present, MUST be silently ignored. 5. Example The following example shows a SIP 404 response message containing a Reason header field with a [Q.850] cause value and a isup-cause- location value. The 404 Response will be set up 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. SIP/2.0 404 Not Found From: Alice ;tag=1234567 To: Bob ;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 Location in Reason header field. 6. Privacy Considerations This document doesn't change any of the privacy considerations described in [RFC3326]. While the addition of the location parameter does provide an indicator of the entity that added the location in the signaling path this provides little more exposure than the [Q.850] cause itself. 7. Security Considerations This document doesn't change any of the security considerations described in [RFC3326]. The addition of the location parameter does provide 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 constrains. But since the [Q.850] location is very imprecise the [Q.850] location value itself will not add any major security constraint. The use of this parameter is not restricted to a specific architecture. Jesske Expires August 16, 2018 [Page 4] Internet-Draft ISUP Release Location Parameter February 2018 8. IANA Considerations 8.1. Registration of location Parameter for Reason header field This document calls for IANA to register a new SIP header parameter as per the guidelines in [RFC3968], which will be added to Header Field Parameters sub-registry under http://www.iana.org/assignments/ sip-parameters. Header Field: Reason Parameter Name: location 9. Acknowledgments Thanks to Michael Kreipl, Thoams Belling, Marianne Mohali, Peter Daws, Paul Kyzivat, Dale Worley, Yehoshua Gev, Keith Drage for the comments and review. 10. Normative References [Q.850] INTERNATIONAL TELECOMMUNICATION UNION, "Usage of cause and location in the Digital Subscriber Signalling System No. 1 and the Signalling System No. 7 ISDN User Part", Q 850, May 1998. [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997, . [RFC3261] Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston, A., Peterson, J., Sparks, R., Handley, M., and E. Schooler, "SIP: Session Initiation Protocol", RFC 3261, DOI 10.17487/RFC3261, June 2002, . [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, . [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, . Jesske Expires August 16, 2018 [Page 5] Internet-Draft ISUP Release Location Parameter February 2018 [RFC5234] Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax Specifications: ABNF", STD 68, RFC 5234, DOI 10.17487/RFC5234, January 2008, . 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 Expires August 16, 2018 [Page 6]