One document matched: draft-jesske-dispatch-req-reason-in-responses-00.txt
dispatch R. Jesske
Internet-Draft L. Liess
Intended status: Informational Deutsche Telekom
Expires: October 1, 2010 March 30, 2010
Requirements for the use of the Reason header filed in Session
Initiation Protocol (SIP) responses
draft-jesske-dispatch-req-reason-in-responses-00
Abstract
Although the use of the Reason header field in responses is
considered in RFC3326, doing so is not specified for any existing
response code. Nonetheless, the Reason header field has been widely
used in responses to carry Q.850 reason codes for failure responses
to INVITEs that have been gatewayed to PSTN systems. This document
specifies and formally permits the use of the Reason header field in
SIP responses to carry Q.850 reason codes for this and other
purposes.
Status of this Memo
This Internet-Draft is submitted to IETF in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF), its areas, and its working groups. Note that
other groups may also distribute working documents as Internet-
Drafts.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
The list of current Internet-Drafts can be accessed at
http://www.ietf.org/ietf/1id-abstracts.txt.
The list of Internet-Draft Shadow Directories can be accessed at
http://www.ietf.org/shadow.html.
This Internet-Draft will expire on October 1, 2010.
Copyright Notice
Copyright (c) 2010 IETF Trust and the persons identified as the
document authors. All rights reserved.
Jesske & Liess Expires October 1, 2010 [Page 1]
Internet-Draft Reason Header March 2010
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(http://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 BSD License.
This document may contain material from IETF Documents or IETF
Contributions published or made publicly available before November
10, 2008. The person(s) controlling the copyright in some of this
material may not have granted the IETF Trust the right to allow
modifications of such material outside the IETF Standards Process.
Without obtaining an adequate license from the person(s) controlling
the copyright in such materials, this document may not be modified
outside the IETF Standards Process, and derivative works of it may
not be created outside the IETF Standards Process, except to format
it for publication as an RFC or to translate it into languages other
than English.
Jesske & Liess Expires October 1, 2010 [Page 2]
Internet-Draft Reason Header March 2010
Table of Contents
1. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Requirements . . . . . . . . . . . . . . . . . . . . . . . . . 4
3.1. Used Cases for the requirements . . . . . . . . . . . . . . 5
4. Overall Applicability . . . . . . . . . . . . . . . . . . . . . 5
5. Example . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
6. Security Considerations . . . . . . . . . . . . . . . . . . . . 8
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 8
8. Normative References . . . . . . . . . . . . . . . . . . . . . 8
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 9
Jesske & Liess Expires October 1, 2010 [Page 3]
Internet-Draft Reason Header March 2010
1. 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].
This document uses terms from [RFC3261].
2. Overview
With introducing the Session Initiation Protocol [RFC3261]into the IP
Multimedia Subsystem (IMS) which is defined by the 3rd Generation
Partnership Project the it was required to interoperate with the
PSTN/ISDN. The European Telecommunication Standards Institute (ETSI)
has defined a Next Generation Network (NGN) where a substantial part
of it is based on the IMS.
ETSI has developed a number of requirements to support the usage of
SIP in Next Generation Networks that interoperate, at the service
level, with the Public Switched Telephone Network (PSTN), the
Integrated Services Digital Network (ISDN), the 3GPP IP Multimedia
Subsystem (IMS), and SIP networks and terminals that implement the
service logic.
Also ITU-T has specified an interworking between SIP and PSTN/ISDN
networks [ITU.Q1912.5.2004] and [TS29.229]where reason within
responses are already supported.
In order to provide full support in SIP of existing services,
extensions to SIP are needed.
This document proposes the use of the Reason header field in
responses. This is needed for creating services that must be
interoperable with the PSTN/ISDN network and the interoperability of
traversing communications through SIP not using SIP-I.
The main used case for reason header within responses are
interworking situations with PSTN/ISDN networks where the ISUP cause
In many cases the mapping of specific cause values will result in a
generic SIP Response like it is shown below.
[RFC3398] and other Interworking specifications like [RFC3326] are
describing the mapping of ISUP Cause Values to SIP and vice versa.
Looking on the specific mapping shows that information will be lost
when the call traverses ISUP without using SIP-T.
Example:
Jesske & Liess Expires October 1, 2010 [Page 4]
Internet-Draft Reason Header March 2010
[RFC3398] describes the mapping of following ISUP Causes to 503 and
408 like follows.
ISUP Cause value SIP response
---------------- ------------
34 no circuit available 503 Service unavailable
38 network out of order 503 Service unavailable
41 temporary failure 503 Service unavailable
42 switching equipment congestion 503 Service unavailable
47 resource unavailable 503 Service unavailable
58 bearer capability not presently 503 Service unavailable
Available
88 incompatible destination 503 Service unavailable
18 no user responding 408 Request Timeout
The mapping back is shown as follows:
Response received Cause value in the REL
----------------- ----------------------
503 Service unavailable 41 Temporary failure
408 Request timeout 102 Recovery on timer
expiry
The Example with 503 shows that a couple of different ISUP Cause
values are interworked to only one SIP response. With 408 the
meaning of the release cause is changed when interworked back to
ISUP. Also Services built on Cause 18 (e.G. a 2nd call attempt on an
other number, this service is like a sequential forking) will not
work.
3. Requirements
REQ-1:
It should be possible to support PSTN-SIP-PSTN scenarios where the
reason of a call release can be transferred though the SIP domain
without any loss of information and no change of reason.
REQ-2:
It should be possible to provide correct announcements to a SIP user
based on the reason for call clearing within the PSTN network or the
PSTN user. The PSTN does normally not provide announcements to
Jesske & Liess Expires October 1, 2010 [Page 5]
Internet-Draft Reason Header March 2010
originating user when clearing the call.
REQ-3:
A UA may have the ability to display ISUP specific release causes or
show a equivalent text. A inclusion of [Q.850] causes is out of
scope.
REQ-4:
A application server providing specific PSTN like services may have
the possibility to include ISUP specific release causes
3.1. Used Cases for the requirements
REQ-1 shows the scenario between two ISUP Gateways where SIP-I is not
a solution to be used. A IMS network defined by 3GPP where SIP-I is
not part of the framework is such an example. A used case is shown
in Figure 2.
REQ-2 identifies the scenario the gateway passes on the cause and
some announcement server translates the cause into the appropriate
announcement.
REQ-3 excludes that a SIP UA includes [Q.850] cause values because
that is not needed due to the different context of a SIP UA and of
course the existing SIP response codes. Also the possibility of
displaying Q.850 causes should be used very restrictive and is not
recommended. A used case could be a used case could be a Integrated
Access Device where a POTS Phone is connected to. It is recommended
to ignore the cause value if received be a UA.
REQ-4: allows an Application Server that is providing specific
Services simulating PSTN services to include Q.850 Causes. This is
needed specific for IMS operators which are substituting their PSTN
to IMS. These operators may run Services in the SIP domain that are
provided to PSTN end users.
4. Overall Applicability
The SIP procedures specified in this document are foreseen for
networks providing simulation services and/or interworking to the
PSTN/ISDN.
The document is describing the use of the Reason header in SIP
responses. These procedures are only valuable if the reason
contained in the element "protocol" is "Q.850". A inclusion of a SIP
Jesske & Liess Expires October 1, 2010 [Page 6]
Internet-Draft Reason Header March 2010
reason (protocol="SIP") is not helpful due to the fact that the
response already provides the SIP reason. The Release Causes are
described within [Q.850]. (Note: The ETSI specifications can be
downloaded under http://pda.etsi.org/pda/queryform.asp free of
charge.)
The appearance of the Reason header is applicable to final responses
3xx, 4xx, 5xx and 6xx and 18x and 199 provisional responses
[I-D.ietf-sipcore-199], the procedures for that are described within
[draft-jesske-dispatch-reason-in-responses-02] .
5. Example
Figure 1 shows the example of SIP interworking with the PSTN/ISDN.
Cause #87 is sent when the connecting user is not member of a Closed
User Group.
A Gateway Proxy AS
| IAM | | |
|------------------>| INVITE | |
| |----------------->| INVITE |
| | 100 Trying |----------------->|
| |<-----------------| 100 Trying |
| | |<-----------------|
| ACK SDP held | | |
|<------------------| | 603 Decline |
| | 603 Decline | Reason Q850 #87 |
| | Reason Q850 #87 | |
| REL Cause #87 | |<-----------------|
| |<-----------------| |
|<----------------- | | |
| | | |
| | | |
| | | |
Figure 1: ISUP-SIP Call
Figure 2 shows the example where the SIP network is used as transit
between PSTN/ISDN networks. This avoids that the Mapping back to the
Q.850 cause within ISUP change the meaning of the reason for release
of the call.
Jesske & Liess Expires October 1, 2010 [Page 7]
Internet-Draft Reason Header March 2010
A Gateway Gateway B
| IAM | | |
|------------------>| INVITE | |
| |----------------->| IAM |
| | 100 Trying |----------------->|
| |<-----------------| 100 Trying |
| | 603 Decline | |
| | Reason Q850 #87 | REL Cause #87 |
| REL Cause #87 | |<-----------------|
| |<-----------------| |
|<----------------- | | |
| | | |
| | | |
| | | |
Figure 2: Transit case
Figure 3 shows the example where the SIP network puts an announcement
towards the UAB. The AS sends an announcement with a specific text
back. After some Time the Response will be sent back to the UA A and
closes all open transactions. With this possibility the SIP user can
informed with more specific information than only the Response code.
A AS Gateway B
| INVITE | | |
|------------------>| INVITE | |
| |----------------->| IAM |
| | 100 Trying |----------------->|
| |<-----------------| |
| | 503 Decline | |
| | Reason Q850 #41 | REL Cause #41 |
| | |<-----------------|
| Announcement |<-----------------| |
|< ================ | | |
| | | |
| 503 after Timeout| | |
|<----------------- | | |
Figure 3: Transit case
Figure 3: Call Release within the PSTN with an announce played within
Jesske & Liess Expires October 1, 2010 [Page 8]
Internet-Draft Reason Header March 2010
the SIP network.
6. Security Considerations
The presence of the Reason header in a response does not affect the
treatment of the response.
Including such a header by an untrusted entity could adulterate the
reactions of the originating entities. E.G. sending back a cause
value "87" can cause an announcement within the PSTN/ISDN saying that
the call was rejected due to the Closed User Group service.
Therefore it is RECOMMENDED to include the Reason header information
in Responses only by trusted entities as it is described within
[RFC3325].
7. IANA Considerations
This document does not have any implications for IANA.
8. Normative References
[I-D.ietf-sipcore-199]
Holmberg, C., "Response Code for Indication of Terminated
Dialog", draft-ietf-sipcore-199-00 (work in progress),
April 2009.
[ITU.Q1912.5.2004]
International Telecommunications Union, "Interworking
between Session Initiation Protocol (SIP) and Bearer
Independent Call Control protocol or ISDN User Part [ITU-T
Recommendation Q.1912.5 (2005)]", ITU Recommendation
Q.1912.5, April 2004.
[Q.850] "Usage of cause and location in the Digital Subscriber
Signalling System No. 1 and the Signalling System No. 7
ISDN User Part [ITU-T Recommendation Q.850]",
ITU Recommendation Q.850, April 1998.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, 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,
Jesske & Liess Expires October 1, 2010 [Page 9]
Internet-Draft Reason Header March 2010
June 2002.
[RFC3325] Jennings, C., Peterson, J., and M. Watson, "Private
Extensions to the Session Initiation Protocol (SIP) for
Asserted Identity within Trusted Networks", RFC 3325,
November 2002.
[RFC3326] Schulzrinne, H., Oran, D., and G. Camarillo, "The Reason
Header Field for the Session Initiation Protocol (SIP)",
RFC 3326, December 2002.
[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, December 2002.
[TS29.229]
"3rd Generation Partnership Project; Technical
Specification Group Core Network and Terminals;
Interworking between the IP Multimedia (IM) Core Network
(CN) subsystem and Circuit Switched (CS) networks (Release
8)".
[draft-jesske-dispatch-reason-in-responses-02]
Jesske, R. and L. Liess, "Use of the Reason header filed
in Session Initiation Protocol (SIP) responses",
March 2010.
Authors' Addresses
Roland Jesske
Deutsche Telekom
Heinrich-Hertz-Strasse 3-7
Darmstadt, 64307
Germany
Phone: +4961516282766
Email: r.jesske@telekom.de
Jesske & Liess Expires October 1, 2010 [Page 10]
Internet-Draft Reason Header March 2010
Laura Liess
Deutsche Telekom
Heinrich-Hertz-Strasse 3-7
Darmstadt, 64307
Germany
Phone: +4961516282761
Email: Laura.Liess@telekom.de
Jesske & Liess Expires October 1, 2010 [Page 11]
| PAFTECH AB 2003-2026 | 2026-04-23 22:11:42 |