wdiff rfc8606.original rfc8606.txt

Sipcore
Internet Engineering Task Force (IETF) R. Jesske
Internet-Draft
Request for Comments: 8606 Deutsche Telekom
Updates: 3326 (if approved) March 13, June 2019
Intended status:
Category: Standards Track
Expires: September 14, 2019

ISUP
ISSN: 2070-1721

ISDN User Part (ISUP) Cause Location Parameter
for the SIP Reason Header Field
draft-ietf-sipcore-reason-q850-loc-07.txt

Abstract

The SIP Reason header field is defined for carrying to carry ISUP (Integrated
Services Digital Network (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 network (Public Switched Telephone Network) to correctly
interpret the reason of release. This document will update
RFC3326. updates RFC 3326 by
adding a location parameter for this purpose.

Status of This Memo

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provisions of BCP 78 and BCP 79.

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This Internet-Draft will expire on September 14, 2019.
https://www.rfc-editor.org/info/rfc8606.

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Table of Contents

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

1. Introduction

The SIP Reason header field specification

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 that a SIP request is carrying the reason of release. The reason
of release indicates why a SIP Dialog or a PSTN call, in case cases where
the call was interworked to the PSTN, was terminated. This The
termination may be a normal termination or a
termination normal, based on a failure within an entity (e.g.
temporary failure) or caused by other reasons like
congestion. factors (e.g., congestion).
The reason may be an a SIP response or an ISUP release cause as
specified within [Q.850]. [RFC6432] specifies that a 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 PTSN the PSTN needs
only to include the location received by the interworking gateway.
[Q.850] describes the definition definitions of the cause code values and the
locations used in ISDN and DSS1 environment. (Digital Subscriber Signalling System
No. 1) environments. The cause code is used for identifying the
reason of release of a call call, and the location identifies where the
call was released.

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 3GPP,
but it is also open to be used by any other network networks that includes include
ISUP interworking gateways and uses use Q.850 reason codes. The purpose
of this parameter is to transport hold the location of the call release so that
it can be transported from the originating PSTN entity to the SIP
entity receiving the via a response or BYE message containing the location of the call release. message. The ISDN location is defined
in [Q.850].

4. Mechanism

As defined by [RFC6432] [RFC6432], any SIP Response message, with the exception
of a 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 4-bit value
which
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.

reason-extension =/ isup-cause-location
isup-cause-location = "location" EQUAL isup-location-value

isup-location-value =
%s"U"
"U" / ; for 0 0 0 0 user
%s"LPN"
"LPN" / ; for 0 0 0 1 private network serving the local user
%s"LN"
"LN" / ; for 0 0 1 0 public network serving the local user
%s"TN"
"TN" / ; for 0 0 1 1 transit network
%s"RLN"
"RLN" / ; for 0 1 0 0 public network serving the remote user
%s"RPN"
"RPN" / ; for 0 1 0 1 private network serving the remote user
%s"LOC-6"
"LOC-6" / ; for 0 1 1 0 spare
%s"INTL"
"INTL" / ; for 0 1 1 1 international network
%s"LOC-8"
"LOC-8" / ; for 1 0 0 0 spare
%s"LOC-9"
"LOC-9" / ; for 1 0 0 1 spare
%s"BI"
"BI" / ; for 1 0 1 0 network beyond interworking point
%s"LOC-11"
"LOC-11" / ; for 1 0 1 1 spare
%s"LOC-12"
"LOC-12" / ; for 1 1 0 0 reserved for national use
%s"LOC-13"
"LOC-13" / ; for 1 1 0 1 reserved for national use
%s"LOC-14"
"LOC-14" / ; for 1 1 1 0 reserved for national use
%s"LOC-15"
"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] as location. Thus
other values [Q.850]. The
'LOC-*' names are not within the scope of this document.

Depending on whether wire codepoints for the message is a request values currently left
as 'spare' or a response '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. This approach is only
possible in cases cause
when the ISUP [Q.850] location is available.

The use of the location parameter is restricted to Q850 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 a an isup-cause-
location value. The 404 Response will be sent when a gateway
receives an ISUP Release release with a [Q.850] cause set to 1, meaning
"Unallocated
Unallocated (unassigned) number", number, i.e., the number is not known in the
PSTN.

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. Header Field

6. Privacy Considerations

While the addition of the location parameter does provide provides an indicator of
the entity that added the location in the signaling path
this 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 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 does
provide
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
location-driven services but does not create any additional security
constrains. But since
constraints. Because the [Q.850] location is very imprecise imprecise, the
[Q.850] location value itself will not add any major security
constraint.
constraints. The use of this parameter is not restricted to a
specific architecture.

[RFC3398] describes detailed security consideration considerations due to
interworking between ISUP and SIP. Beyond these considerations considerations, the
addition of the location does not add additional introduce new security concerns.
The location shows the network part where the call is was released.
Knowing this does not increase the possibilities of extended fraud
scenarios.

8. IANA Considerations

8.1. Registration of location the Location Parameter for the Reason header field

This document calls for Header Field

IANA to register has registered a new SIP header parameter
as 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], which will be added to Header
Field Parameters sub-registry under http://www.iana.org/assignments/
sip-parameters. [RFC3968]:

Header Field: Reason

Parameter Name: location

Predefined Values: yes Yes

Reference: RFCXXXX

Note to RFC Editor: Please replace RFC XXXX with the RFC number of
this specification. 8606

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, ITU-T, "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. 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>.

[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, Thoams 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