Internet DRAFT - draft-jesske-dispatch-reason-loc-q850
draft-jesske-dispatch-reason-loc-q850
Dispatch R. Jesske
Internet-Draft Deutsche Telekom
Updates: RFC6442 (if approved) February 10, 2017
Intended status: Standards Track
Expires: August 14, 2017
Location Parameter for the SIP Reason Header Field
draft-jesske-dispatch-reason-loc-q850-00.txt
Abstract
The SIP Reason header field is defined for Q.850 cause values. Some
services in SIP networks may need to know the location where the call
was released in the PSTN network to correctly interpret the reason of
release.
Status of This Memo
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This Internet-Draft will expire on August 14, 2017.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 2
3. Rationale . . . . . . . . . . . . . . . . . . . . . . . . . . 2
4. Mechanism . . . . . . . . . . . . . . . . . . . . . . . . . . 3
5. Example . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
6. Privacy Considerations . . . . . . . . . . . . . . . . . . . 4
7. Security Considerations . . . . . . . . . . . . . . . . . . . 4
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 4
8.1. Registration of resp-location Parameter for reason header
field . . . . . . . . . . . . . . . . . . . . . . . . . . 4
9. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 5
10. References . . . . . . . . . . . . . . . . . . . . . . . . . 5
10.1. Normative References . . . . . . . . . . . . . . . . . . 5
10.2. Informative References . . . . . . . . . . . . . . . . . 5
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 5
1. Introduction
The SIP Reason header field specification [RFC3326] describes a SIP
header field that is used to indicate that a SIP request or response
is carrying the reason of release. The 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 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 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 BYE message containing the location
of the call release. The ISDN location is defined in [Q.850].
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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 location value
defined in [Q.850] to the Reason header field that identifies the
location of the call release in ISUP as defined in [Q.850] . The
Augmented BNF (ABNF) [RFC5234] for this parameter is shown in
Figure 1.
reason-extension =/ resp-location
resp-location = "location" EQUAL string
The values to be used as location are:
U for user
LPN for private network serving the local user
LN for public network serving the local user
TN for transit network
RLN for public network serving the remote user
RPN for private network serving the remote user
INTL for international network
BI for network beyond interworking point
Figure 1: resp-location
Depending on the direction the UAC or UAS shall include the resp-
location 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.
5. Example
The following example shows a SIP 404 response message containing a
Reason header field with a Q.850 cause value and a resp-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.
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404 Not Found
SIP/2.0 404 Not Found
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 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 resp-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 resp-location parameter
does provide an indicator of the location where the call was release
within the PSTN. This information my be used for specific location
driven services but does not create any additional security
constrains. But since the location is very imprecise the location
value itself will not add any major security constrain. The use of
this parameter is not restricted to a specific architecture.
8. IANA Considerations
8.1. Registration of resp-location Parameter for reason header field
This document calls for IANA to register a new SIP header parameter
as per the guidelines in [RFC3261], which will be added to header
sub-registry under http://www.iana.org/assignments/sip-parameters.
Header Field: Reason
Parameter Name: resp-location
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9. Acknowledgments
Thanks to Michael Kreipel for his comments and review.
10. References
10.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<http://www.rfc-editor.org/info/rfc2119>.
[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,
<http://www.rfc-editor.org/info/rfc3261>.
[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,
<http://www.rfc-editor.org/info/rfc3326>.
[RFC5234] Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax
Specifications: ABNF", STD 68, RFC 5234,
DOI 10.17487/RFC5234, January 2008,
<http://www.rfc-editor.org/info/rfc5234>.
10.2. Informative 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.
Author's Address
Roland Jesske
Deutsche Telekom
Heinrich-Hertz Str, 3-7
Darmstadt 64295
Germany
Email: r.jesske@telekom.de
URI: www.telekom.de
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