SIPCORE Working Group M. Mohali
Internet-Draft Orange
Updates: 5502 (if approved) September 27, 2017
Intended status: Informational
Expires: March 31, 2018
A P-Served-User Header Field Parameter for Originating CDIV session case
in Session Initiation Protocol (SIP)
draft-ietf-sipcore-originating-cdiv-parameter-01
Abstract
This specification defines a new parameter of the P-Served-User
header field in the Session Initiation Protocol (SIP). This new
"orig-cdiv" parameter defines the session case used by a proxy when
handling an originating session after Call Diversion (CDIV) services
has been invoked for the served user. The P-Served-User header field
is defined in RFC5502 to convey the identity of the served user and
the session case that applies to this particular communication
session and application invocation. This document updates RFC5502 to
add the "originating after CDIV" session case and to provide more
guidance for using the P-Served-User header field in IP networks that
were missing in RFC5502.
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/.
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."
This Internet-Draft will expire on March 31, 2018.
Copyright Notice
Copyright (c) 2017 IETF Trust and the persons identified as the
document authors. All rights reserved.
Mohali Expires March 31, 2018 [Page 1]
Internet-Draft P-Served-User parameter orig-cdiv September 2017
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.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. General . . . . . . . . . . . . . . . . . . . . . . . . . 2
1.2. Basic Use Case . . . . . . . . . . . . . . . . . . . . . 3
1.3. Problem Statement . . . . . . . . . . . . . . . . . . . . 4
2. Proxy behavior and parameter handling . . . . . . . . . . . . 4
3. Applicability . . . . . . . . . . . . . . . . . . . . . . . . 6
4. Syntax . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
4.1. General . . . . . . . . . . . . . . . . . . . . . . . . . 6
4.2. ABNF . . . . . . . . . . . . . . . . . . . . . . . . . . 6
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7
6. Call Flow Examples . . . . . . . . . . . . . . . . . . . . . 8
6.1. Call diversion case . . . . . . . . . . . . . . . . . . . 8
6.2. Call diversion and privacy . . . . . . . . . . . . . . . 9
7. Security Considerations . . . . . . . . . . . . . . . . . . . 11
8. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 11
9. References . . . . . . . . . . . . . . . . . . . . . . . . . 11
9.1. Normative References . . . . . . . . . . . . . . . . . . 11
9.2. Informative References . . . . . . . . . . . . . . . . . 12
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 12
1. Introduction
1.1. General
The P-Served-User header field was defined in [RFC5502] to address an
issue that was found in the 3rd Generation Partnership Project (3GPP)
IMS (IP Multimedia Subsystem) between an S-CSCF (Serving Call Session
Control Function) and an AS (Application Server) on the ISC (IMS
Service Control) interface. For more information on the IMS, a
detailed description can be found in [TS.3GPP.24.229].
The P-Served-User header field conveys the identity of the served
user, his/her registration state and the session case that applies to
this particular communication session and application invocation.
Mohali Expires March 31, 2018 [Page 2]
Internet-Draft P-Served-User parameter orig-cdiv September 2017
[RFC5502] defines the originating and terminating session cases for a
registered or unregistered user. This document extends the P-Served-
User header field to include the session case for a forwarded leg
when a call diversion service (CDIV) has been invoked and if an
originating service of the diverting user has to be triggered.
The sessioncase-param parameter of the P-Served-User header field is
extended with the "orig-cdiv" parameter for this "originating after
CDIV" session case.
The following section defines usage of the "orig-cdiv" parameter of
P-Served-User header field, Section 2 specifies the proxy behavior
for handling the new header field parameter, and Section 3 discusses
the applicability and scope of this new header field parameter.
Section 4 describes the syntax and correct the syntax of [RFC5502],
Section 5 registers the P-Served-User header field parameters with
IANA, and Section 6 discusses the security properties of the
environment where this new header field parameter is intended to be
used.
1.2. Basic Use Case
In the 3GPP IMS (IP Multimedia Subsystem), the S-CSCF (Serving CSCF)
is a SIP proxy that serves as a registrar and handles originating and
terminating session states for users allocated to it. This means
that any call that is originated by a specific user or any call that
is terminated to that specific user will pass through the S-CSCF that
is allocated to that user.
At the moment that an S-CSCF is allocated for a specific user, the
user profile is downloaded from the HSS (Home Subscriber Server) to
this S-CSCF, see [TS.3GPP.29.228]. The user profile contains the
list of actions to be taken by the S-CSCF for the served user
depending on the session direction (originating or terminating) and
the user state (registered or not) in the IMS network. With this
user profile, the S-CSCF determines the current case and apply the
corresponding actions such as forward the request to an AS. At its
turn, the AS has to go through a similar process of determining who
is the current served user, what is his/her "registration state" and
on which "session case" is the session. [RFC5502] defines all those
parameters and in particular the originating and terminating session
cases.
In basic call scenarios, the is no particular issue for the S-CSCF
and AS to know which scenario needs to be realized but in case of
call diversion services for which the session is re-targeted, the
session cases defined in [RFC5502] poses some limitations as
described in the following section.
Mohali Expires March 31, 2018 [Page 3]
Internet-Draft P-Served-User parameter orig-cdiv September 2017
1.3. Problem Statement
In case of a call diversion service, the received request is first
considered as a terminating session case and the terminating filter
criteria configured in the S-CSCF are performed. Receiving the call
initiation request, the Application Server is able to determine the
served user and the session case (here "term") from the received P-
Served-User header field content and to execute terminating services.
When the call diversion service is executed (as a terminating
service), the Application Server changes the target (Request-URI) of
the session and a new call leg is created. This new call leg could
be considered as an originating call leg from the diverting user but
this is not the case. Indeed, the originating user remains the same
and some of the diverting user's originating services should not be
triggered as if it was an originating call. For instance, the
originating user identity should not be restricted because the
diverting user has a privacy service for his/her own identity. The
privacy of the diverting user should apply to information related to
this user (eg. in the Histroy-Info header field). In the same
manner, some specific services will need to be specifically triggered
on the outgoing leg after a call diversion. Without a dedicated
session case for originating after CDIV, there is no possiblity for a
proxy to trigger an originating service for the diverting user or for
an Application Server to execute the procedures for this particular
session case.
For this use case, this document creates a new parameter for the
originating after CDIV session case to be embedded in the P-Served-
User header field.
2. Proxy behavior and parameter handling
The "orig-cdiv" header field parameter can be used inside a trust
domain of the P-Served-User header field by proxies that are
processing call diversion services. The following section
illustrates how this header field parameter can be used in a 3GPP
network.
For a terminating call, when receiving the initial INVITE request,
the S-CSCF will determine that the session case is for a terminating
user as described in [RFC5502], then it determines the served user by
looking at the Request-URI and saves this Request-URI. After that,
the S-CSCF starts the analysis of filter criteria and triggers the
served user Application Server for the terminating services to be
executed including in the INVITE request the P-Served-User header
field with the "sescase" parameter set to "term" and the regstate to
the corresponding value.
Mohali Expires March 31, 2018 [Page 4]
Internet-Draft P-Served-User parameter orig-cdiv September 2017
Based on some criteria, the Application Server concludes that the
request has to be diverted to another target user or application.
The received Request-URI is then replaced with the new diverted-to
address. The Application Server stores the successive Request-URI(s)
values by adding one or two History-Info header field entry(ies)
[RFC7044] in the outgoing INVITE. In the History-Info header field,
the served user address is tagged thanks to the mp-param header field
parameter added in entry associated to the diverted-to address
created.
In the next step, the Application Server forwards the INVITE request
back to the S-CSCF. When receiving back the INVITE request, the
S-CSCF can see that the topmost Route header field contains its own
hostname but the Request-URI does not match the saved Request-URI.
In this case, the S-CSCF updates the P-Served-User header field
content by replacing the "sescase" parameter by the "orig-cdiv"
parameter. The PServedUser-value remains unchanged.
Then the procedure continues by forwarding the INVITE request over to
an AS that hosts the originating services of the served user
(diverting user) that specifically need to be executed on the
forwarded leg after a call diversion service.
When the Application Server receives the INVITE request, it
determines that the session case is for "orig-cdiv" session case and
will perform the originating services to be executed after
retargeting for the diverting user (i.e. served user).
This document also provides the following guidance that reminds or
clarifies the P-Served-User handling that are missing in [RFC5502]:
o This header is forbidden to be repeated within a request for a
particular session at a particular time for the reason that
session cases are mutually exclusive. This document updates
[RFC5502] to clearly state that P-Served-User header field MUST
not contain different values either comma-separated or header-
separated. This documents also updates the syntax of the header
as defined in [RFC5502] to reflect this uniqueness of parameters
values.
o Whether the "regstate" parameter is removed or not by the S-CSCF
when processing the orginating after CDIV session case is out of
the scope of this document. In one hand, it can either be
considered that the S-CSCF is able to store the previous regstate
value and that the same value applies or that the "regstate" is
not relevant after a diverting service. On the other hand, the
regstate can be combined to the orig-cdiv session case to provide
Mohali Expires March 31, 2018 [Page 5]
Internet-Draft P-Served-User parameter orig-cdiv September 2017
different services if the served user is registered or
unregistered. These choices are implementation dependent.
3. Applicability
The use of the P-Served-User header field extensions is only
applicable inside a Trust Domain for P-Served-User. Nodes in such a
Trust Domain explicitly trust each other to convey the served user
and to be responsible for withholding that information outside of the
Trust Domain. The means by which the network determines the served
user and the policies that are executed for a specific served user is
outside the scope of this document.
4. Syntax
4.1. General
[RFC5502] defines the P-Served-User header field with the
sessioncase-param parameter "sescase" which is specified as having
"orig" and "term" predefined values. This document defines an
additional parameter for the sessioncase-param: "orig-cdiv".
Because this document extends the existing sessioncase-param
parameter in a special way and that it has been identified errors in
the syntax of the P-Served-User header field as defined in [RFC5502],
this document corrects and extends the header at the same time.
The extension of the sessioncase-param parameter to add the "orig-
cdiv" session case is done in a way to fit the parameter format
introduced in release 11 of the 3GPP [TS.3GPP.24.229] and keep a
backward compatibility.
"EQUAL", "HCOLON", "SEMI", "name-addr", "addr-spec", and "generic-
param" are defined in [RFC3261].
4.2. ABNF
The augmented Backus-Naur Form (ABNF) [RFC5234] syntax of the P-
Served-User header field is described in [RFC5502].
This document updates [RFC5502] to correct the P-Served-User header
field ABNF syntax and extend it as following:
Mohali Expires March 31, 2018 [Page 6]
Internet-Draft P-Served-User parameter orig-cdiv September 2017
P-Served-User = "P-Served-User" HCOLON PServedUser-value
*(SEMI served-user-param)
served-user-param = sessioncase-param
/ registration-state-param
/ generic-param
PServedUser-value = name-addr / addr-spec
sessioncase-param = 1("sescase" EQUAL 1("orig" / "term")/ orig-cdiv)
registration-state-param = "regstate" EQUAL 1("unreg" / "reg")
orig-cdiv = "orig-cdiv"
Examples of possible P-Served-User header field:
P-Served-User: <sip:user@example.com>; orig-cdiv; regstate=reg
or
P-Served-User: <sip:user@example.com>; orig-cdiv
or
P-Served-User: <sip:user@example.com>; sescase=term; regstate=unreg
5. IANA Considerations
The syntax of the P-Served-User header field is defined in [RFC5502]
and updated in Section 4 of this document.
This document requests IANA to update the existing row for the P-
Served-User header field in the "Header Fields" sub-registry:
Header Name Compact Form Reference
------------- ------------ ----------------
P-Served-User none [RFC5502][RFCXXXX]
Note to RFC Editor: Please replace XXXX with the RFC number of this document.
This document requests IANA to add new rows for the P-Served-User
header field parameters in the "Header Field Parameters and Parameter
Values" sub-registry as per the registry created by [RFC3968]:
Header Field Parameter Name Predefined Values Reference
-------------- ---------------- ----------------- -----------------
P-Served-User sescase Yes [RFC5502][RFCXXXX]
P-Served-User regstate Yes [RFC5502][RFCXXXX]
P-Served-User orig-cdiv No [RFCXXXX]
Note to RFC Editor: Please replace XXXX with the RFC number of this document.
Mohali Expires March 31, 2018 [Page 7]
Internet-Draft P-Served-User parameter orig-cdiv September 2017
6. Call Flow Examples
6.1. Call diversion case
The following call flow shows a session establishement for Alice
calls Bob which has a call diversion when busy towards Carol.
proxy server UA
Alice Bob's...S-CSCF-B..........AS-B.............Bob Carol
| | | | |
| INVITE F1 | | | |
|--------------->| INVITE F2 | | |
| |--------------->| | |
| | INVITE F3 | | |
| |<---------------| INVITE F4 | |
| |-------------------------------->| |
| | 486 F5 | |
| |<--------------------------------| |
| | 486 F6 | | |
| |--------------->| | |
| | INVITE F7 | | |
| |<---------------| | |
| | INVITE F8 | | |
| |--------------->| | |
| | INVITE F9 | | |
| |<---------------| INVITE F10 |
| |------------------------------------------------->|
| | | | |
| | | | 180 F11 |
| | | 180 F12 |<---------------|
| | 180 F13 |<---------------| |
| 180 F14 |<---------------| | |
|<---------------| | | |
| | | | |
F1 INVITE Alice -> S-CSCF-B
INVITE sip:bob@example.com SIP/2.0
From: Alice <sip:alice@domaina.com>;tag=1928301774
To: Bob <sip:bob@example.com>
F2 INVITE S-CSCF-B -> AS-B
INVITE sip:bob@example.com SIP/2.0
From: Alice <sip:alice@domaina.com>;tag=1928301774
To: Bob <sip:bob@example.com>
P-Served-User: <sip:bob@example.com>; term; regstate=reg
F3 INVITE AS-B -> S-CSCF-B
INVITE sip:bob@example.com SIP/2.0
Mohali Expires March 31, 2018 [Page 8]
Internet-Draft P-Served-User parameter orig-cdiv September 2017
From: Alice <sip:alice@domaina.com>;tag=1928301774
To: Bob <sip:bob@example.com>
P-Served-User: <sip:bob@example.com>; term; regstate=reg
F4 INVITE S-CSCF-B -> Bob
INVITE sip:bob@192.0.2.4 SIP/2.0
From: Alice <sip:alice@domaina.com>;tag=1928301774
To: Bob <sip:bob@example.com>
P-Served-User: <sip:bob@example.com>; term; regstate=reg
F5-F6 486 BUSY Bob -> S-CSCF-B -> AS-B
486 BUSY
From: Alice <sip:alice@domaina.com>;tag=1928301774
To: Bob <sip:bob@example.com>;tag=es43sd
F7 INVITE AS-B -> S-CSCF-B
INVITE sip:Carol@domainc.com SIP/2.0
From: Alice <sip:alice@domaina.com>;tag=1928301774
To: Bob <sip:bob@example.com>
P-Served-User: <sip:bob@example.com>; term; regstate=reg
F8 INVITE S-CSCF-B -> AS-B
INVITE sip:Carol@domainc.com SIP/2.0
From: Alice <sip:alice@domaina.com>;tag=1928301774
To: Bob <sip:bob@example.com>
P-Served-User: <sip:bob@example.com>; orig-cdiv; regstate=reg
F9 INVITE AS-B -> S-CSCF-B
INVITE sip:carol@domainc.com SIP/2.0
From: Alice <sip:alice@domaina.com>;tag=1928301774
To: Bob <sip:bob@example.com>
P-Served-User: <sip:bob@example.com>; orig-cdiv; regstate=reg
F10 INVITE S-CSCF-B -> Carol
INVITE sip:carol@192.0.2.7 SIP/2.0
From: Alice <sip:alice@domaina.com>;tag=1928301774
To: Bob <sip:bob@example.com>
Figure 1: P-Served-User during call diversion service
6.2. Call diversion and privacy
The following call flow shows a call diversion use case for which
Alice has no identity restriction service and Bob has an
unconditional call diversion service towards Carol and an identity
presentation restriction service.
Mohali Expires March 31, 2018 [Page 9]
Internet-Draft P-Served-User parameter orig-cdiv September 2017
proxy server UA
Alice Bob's...S-CSCF-B..........AS-B.............Bob Carol
| | | | |
| INVITE F1 | | | |
|--------------->| INVITE F2 | | |
| |--------------->| | |
| | INVITE F3 | | |
| |<---------------| | |
| | INVITE F4 | | |
| |--------------->| | |
| | INVITE F5 | | |
| |<---------------| INVITE F6 | |
| |------------------------------------------------->|
| | | | |
| | | | 180 F7 |
| | | 180 F8 |<---------------|
| | 180 F9 |<---------------| |
| 180 F10 |<---------------| | |
|<---------------| | | |
| | | | |
F1 INVITE Alice -> S-CSCF-B
INVITE sip:bob@example.com SIP/2.0
From: Alice <sip:alice@domaina.com>;tag=1928301774
To: Bob <sip:bob@example.com>
Supported: histinfo
F2 INVITE S-CSCF-B -> AS-B
INVITE sip:bob@example.com SIP/2.0
From: Alice <sip:alice@domaina.com>;tag=1928301774
To: Bob <sip:bob@example.com>
P-Served-User: <sip:bob@example.com>; term; regstate=reg
F3 INVITE AS-B -> S-CSCF-B
INVITE sip:carol@domainc.com SIP/2.0
From: Alice <sip:alice@domaina.com>;tag=1928301774
To: Carol <sip:carol@domainc.com>
P-Served-User: <sip:bob@example.com>; term; regstate=reg
History-Info:
<sip:bob@example.com>;index=1,
<sip:carol@domainc.com;cause=302>;index=1.1;mp=1
F4 INVITE S-CSCF-B -> AS-B
INVITE sip:carol@domainc.com SIP/2.0
From: Alice <sip:alice@domaina.com>;tag=1928301774
To: Carol <sip:carol@domainc.com>
P-Served-User: <sip:bob@example.com>; orig-cdiv; regstate=reg
History-Info:
Mohali Expires March 31, 2018 [Page 10]
Internet-Draft P-Served-User parameter orig-cdiv September 2017
<sip:bob@example.com>;index=1,
<sip:carol@domainc.com;cause=302>;index=1.1;mp=1
F5 INVITE AS-B -> S-CSCF-B
INVITE sip:carol@domainc.com SIP/2.0
From: Alice <sip:alice@domaina.com>;tag=1928301774
To: Carol <sip:carol@domainc.com>
P-Served-User: <sip:bob@example.com>; orig-cdiv; regstate=reg
History-Info:
<sip:bob@example.com?privacy=history>;index=1,
<sip:carol@domainc.com;cause=302>;index=1.1;mp=1
F6 INVITE S-CSCF-B -> Carol
INVITE sip:carol@192.0.2.7 SIP/2.0
From: Alice <sip:alice@domaina.com>;tag=1928301774
To: Carol <sip:carol@domainc.com>
History-Info:
<sip:bob@example.com?privacy=history>;index=1,
<sip:carol@domainc.com;cause=302>;index=1.1;mp=1
<sip:carol@192.0.2.7>;index=1.1.1;rc=1.1
Figure 2: P-Served-User when privacy requested
7. Security Considerations
The security considerations in [RFC5502] apply.
As the "orig-cdiv" parameter of P-Served-User header field can be
used to trigger applications, it is important to ensure that the
parameter has not been added to the SIP message by an unauthorized
SIP entity.
8. Acknowledgments
The author wishes to thank the 3GPP community for providing guidance,
input, and comments on the document. Thanks also to Dale Worley for
his careful review of the document. A special thanks to Christer
Holmberg.
9. References
9.1. Normative References
Mohali Expires March 31, 2018 [Page 11]
Internet-Draft P-Served-User parameter orig-cdiv September 2017
[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,
<https://www.rfc-editor.org/info/rfc3261>.
[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>.
[RFC7044] Barnes, M., Audet, F., Schubert, S., van Elburg, J., and
C. Holmberg, "An Extension to the Session Initiation
Protocol (SIP) for Request History Information", RFC 7044,
DOI 10.17487/RFC7044, February 2014,
<https://www.rfc-editor.org/info/rfc7044>.
9.2. Informative References
[RFC5502] van Elburg, J., "The SIP P-Served-User Private-Header
(P-Header) for the 3GPP IP Multimedia (IM) Core Network
(CN) Subsystem", RFC 5502, DOI 10.17487/RFC5502, April
2009, <https://www.rfc-editor.org/info/rfc5502>.
[TS.3GPP.24.229]
3GPP, "IP multimedia call control protocol based on
Session Initiation Protocol (SIP) and Session Description
Protocol (SDP);Stage 3", 3GPP TS 24.229 v11.
[TS.3GPP.29.228]
3GPP, "IP Multimedia (IM) Subsystem Cx and Dx interfaces;
Signalling flows and message contents", 3GPP TS 29.228
v11.
Author's Address
Mohali Expires March 31, 2018 [Page 12]
Internet-Draft P-Served-User parameter orig-cdiv September 2017
Marianne Mohali
Orange
Orange Gardens, 44 avenue de la Republique
Chatillon 92326
France
Email: marianne.mohali@orange.com
Mohali Expires March 31, 2018 [Page 13]
