Internet DRAFT - draft-ietf-sipcore-originating-cdiv-parameter
draft-ietf-sipcore-originating-cdiv-parameter
SIPCORE Working Group M. Mohali
Internet-Draft Orange
Updates: 5502 (if approved) December 10, 2018
Intended status: Informational
Expires: June 13, 2019
A P-Served-User Header Field Parameter for Originating CDIV session case
in Session Initiation Protocol (SIP)
draft-ietf-sipcore-originating-cdiv-parameter-08
Abstract
The P-Served-User header field was defined based on a requirement
from 3rd Generation Partnership Project (3GPP) IMS (IP Multimedia
Subsystem) in order to convey the identity of the served user, his/
her registration state and the session case that applies to this
particular communication session and application invocation. A
session case is metadata that captures the status of the session of a
served user: whether the served user is registered or not, and
whether the session originates or terminates with the served user.
This document updates RFC5502 by defining a new P-Served-User header
field parameter, "orig-cdiv". The parameter conveys the session case
used by a proxy when handling an originating session after Call
Diversion (CDIV) services have been invoked for the served user.
This document also fixes the ABNF in RFC 5502 and provides more
guidance for using the P-Served-User header field in IP networks.
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 June 13, 2019.
Mohali Expires June 13, 2019 [Page 1]
Internet-Draft P-Served-User parameter orig-cdiv December 2018
Copyright Notice
Copyright (c) 2018 IETF Trust and the persons identified as the
document authors. All rights reserved.
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.
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.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. General . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.2. Basic Use Case . . . . . . . . . . . . . . . . . . . . . 3
1.3. Problem Statement . . . . . . . . . . . . . . . . . . . . 4
2. Conventions and Terminology . . . . . . . . . . . . . . . . . 5
3. Applicability . . . . . . . . . . . . . . . . . . . . . . . . 5
4. Proxy behavior and parameter handling . . . . . . . . . . . . 5
5. Clarification of RFC5502 procedures . . . . . . . . . . . . . 6
6. Syntax . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
6.1. General . . . . . . . . . . . . . . . . . . . . . . . . . 7
6.2. ABNF . . . . . . . . . . . . . . . . . . . . . . . . . . 7
7. Call Flow Examples . . . . . . . . . . . . . . . . . . . . . 8
7.1. Call diversion case . . . . . . . . . . . . . . . . . . . 8
7.2. Call diversion and privacy . . . . . . . . . . . . . . . 10
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 12
9. Security Considerations . . . . . . . . . . . . . . . . . . . 12
10. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 13
11. References . . . . . . . . . . . . . . . . . . . . . . . . . 13
11.1. Normative References . . . . . . . . . . . . . . . . . . 13
Mohali Expires June 13, 2019 [Page 2]
Internet-Draft P-Served-User parameter orig-cdiv December 2018
11.2. Informative References . . . . . . . . . . . . . . . . . 14
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 14
1. Introduction
1.1. General
The P-Served-User header field [RFC5502] was defined based on a
requirement from 3rd Generation Partnership Project (3GPP) IMS (IP
Multimedia Subsystem) in order to convey the identity of the served
user, his/her registration state and the session case between an
Serving Call Session Control Function (S-CSCF) and an Application
Server (AS) on the IMS Service Control (ISC) interface. A session
case is metadata that captures the status of the session of a served
user: whether the served user is registered or not, and whether the
session originates or terminates with the served user. For more
information on session cases and the IMS, a detailed description can
be found in [TS.3GPP.24.229].
[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 3 discusses the applicability and
scope of this new header field parameter, and Section 4 specifies the
proxy behavior for handling the new header field parameter.
Section 5 clarifies some of the [RFC5502] procedures, Section 6
describes the extended syntax and corrects the syntax of [RFC5502],
Section 8 registers the P-Served-User header field parameters with
IANA, Section 7 gives some examples, and Section 9 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 assigned 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
assigned to that user.
Mohali Expires June 13, 2019 [Page 3]
Internet-Draft P-Served-User parameter orig-cdiv December 2018
At the moment that an S-CSCF is assigned to a specific user, the user
profile is downloaded from the Home Subscriber Server (HSS) 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 applies the corresponding
actions such as forwarding the request to an AS. The AS then goes
through a similar process of determining who is the current served
user, what is his/her "registration state", and what is the "session
case" of the session. [RFC5502] defines all those parameters and in
particular the originating and terminating session cases.
In basic call scenarios, there 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] pose some limitations as described
in the following section.
1.3. Problem Statement
To illustrate the problem statement, let's imagine Alice trying to
call Bob and Bob having a call diversion service activated towards
Carol's address. In the case of a call diversion service, the
received request is first treated as a terminating session case (at
Bob side), and the terminating filter criteria configured in the
S-CSCF are performed. A filter criteria is information in the user
profile that determines whether an initial request is sent to a
particular AS. When the AS receives the call initiation request, the
AS is able to determine the served user (Bob) 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 of Bob), the AS changes the
target (Request-URI) of the session (toward Carol's address) and a
new call leg is created. The served user becomes the diverting user.
This new call leg could be considered as an originating call leg from
the diverting user (Bob) but this is not the case. Indeed, the
originating user remains the same (Alice), 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
(Alice) should not be restricted because the diverting user (Bob) has
a privacy service for his own identity. The privacy of the diverting
user should apply to information related to this user only (eg. in
the History-Info header field). In the same manner, some specific
services will need to be triggered on the outgoing leg after a call
diversion. Without a dedicated session case for originating-after-
CDIV, the S-CSCF cannot trigger an originating service for the
Mohali Expires June 13, 2019 [Page 4]
Internet-Draft P-Served-User parameter orig-cdiv December 2018
diverting user, nor can an AS execute the procedures for this
particular session case.
For this use case, this document creates a new parameter ("orig-
cdiv") for the originating-after-CDIV session case to be embedded in
the P-Served-User header field.
2. Conventions and 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. Applicability
The use of the P-Served-User header field extensions is only
applicable inside a Trust Domain [RFC3324] for the P-Served-User
header field. 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. Proxy behavior and parameter handling
The following section illustrates how this header field parameter can
be used in a 3GPP network.
For a terminating call, the following steps will be followed:
1. The S-CSCF receives the initial INVITE request for a terminating
call and determines that the session case is for a terminating
user as described in [RFC5502];
2. The S-CSCF determines who is the served user by looking at the
Request-URI and saves the current Request-URI;
3. The S-CSCF analyzes the filter criteria. It then sends the
request to the AS of the served user as an INVITE that includes
the P-Served-User header field with the "sescase" parameter set
to "term" and the "regstate" set to the corresponding value in
order to trigger execution of terminating services;
4. Based on some criteria, the AS concludes that the request has to
be diverted to another target user or application. The AS
replaces the received Request-URI with the new diverted-to
Mohali Expires June 13, 2019 [Page 5]
Internet-Draft P-Served-User parameter orig-cdiv December 2018
address and the AS 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 using the mp-param header field
parameter added in entry associated to the diverted-to address
created. The AS forwards the INVITE request back to the S-CSCF;
5. 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 with the "orig-cdiv" parameter.
The P-Served-User header field value remains unchanged;
6. The S-CSCF forwards the INVITE request to an AS that hosts the
originating services of the served user (diverting user) that
need to be executed on the forwarded leg after a call diversion
service;
7. When the AS receives the INVITE request, it determines that the
session case is for "orig-cdiv" session case and performs the
originating services to be executed after retargeting for the
diverting user (i.e. served user).
5. Clarification of RFC5502 procedures
This document provides the following guidance for the handling of the
P-Served-User header field that are missing in [RFC5502]:
o The P-Served-User header field MUST NOT 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 the P-Served-User header
field MUST NOT contain multiple values either comma-separated or
header-separated. This documents also updates the syntax of the
header from [RFC5502] to reflect this uniqueness of parameters
values.
o [RFC5502] does not clearly state what to do with the received P-
Served-User header field when a call is diverted to another
destination. This document highlights that there are several ways
of handling the P-Served-User header field: the S-CSCF could store
the previous "regstate" value and decide that the same value
applies; or the "regstate" may no longer be relevant after a
diverting service so the S-CSCF removes it; or the regstate could
be combined with the orig-cdiv session case to provide different
services depending on whether the served user is registered or
unregistered. These choices are implementation dependent.
Mohali Expires June 13, 2019 [Page 6]
Internet-Draft P-Served-User parameter orig-cdiv December 2018
6. Syntax
6.1. 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, and because errors have been identified in the syntax,
this document corrects and extends the P-Served-User header field.
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 to maintain
a backward compatibility.
"EQUAL", "HCOLON", "SEMI", "name-addr", "addr-spec", and "generic-
param" are defined in [RFC3261].
6.2. 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:
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 = "sescase" EQUAL ("orig"/"term")/ orig-cdiv
registration-state-param = "regstate" EQUAL ("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
Mohali Expires June 13, 2019 [Page 7]
Internet-Draft P-Served-User parameter orig-cdiv December 2018
This document allows choosing between addr-spec and name-addr when
constructing the header field value. As specified in RFC 8217, the
"addr-spec" form MUST NOT be used if its value would contain a comma,
semicolon, or question mark [RFC8217].
7. Call Flow Examples
7.1. Call diversion case
The following call flow shows a session establishment when Alice
calls Bob, who has a call diversion service that diverts to Carol
when Bob is busy.
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 |<---------------| | |
|<---------------| | | |
| | | | |
[Alice calls Bob]
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>
Mohali Expires June 13, 2019 [Page 8]
Internet-Draft P-Served-User parameter orig-cdiv December 2018
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
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
[Bob is busy. His call diversion when busy is invoked towards Carol]
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
[Alice's call is diverted to Carol]
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
[Forwarded leg to Carol is identified as an originating call after
diversion that should not trigger all Bob's originating services]
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
Mohali Expires June 13, 2019 [Page 9]
Internet-Draft P-Served-User parameter orig-cdiv December 2018
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
7.2. 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.
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 |<---------------| | |
|<---------------| | | |
| | | | |
[Alice calls Bob]
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>
Mohali Expires June 13, 2019 [Page 10]
Internet-Draft P-Served-User parameter orig-cdiv December 2018
P-Served-User: <sip:bob@example.com>; term; regstate=reg
[Bob's unconditional call diversion to Carol is triggered]
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
[Alice's call is diverted to Carol]
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:
<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
[Forwarded leg to Carol is identified as an originating call after
diversion that allows to apply Bob's privacy request to his identity
within the Histroy-Info header field]
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
Mohali Expires June 13, 2019 [Page 11]
Internet-Draft P-Served-User parameter orig-cdiv December 2018
8. IANA Considerations
The syntax of the P-Served-User header field [RFC5502] is 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 within
the "Session Initiation Protocol (SIP) Parameters" 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 within the "Session Initiation Protocol (SIP)
Parameters" registry: as per the registry created by [RFC3968]:
Header Field Parameter Name Predefined Values Reference
-------------- ---------------- ----------------- -----------------
P-Served-User sescase Yes [RFC5502]
P-Served-User regstate Yes [RFC5502]
P-Served-User orig-cdiv No [RFCXXXX]
Note to RFC Editor: Please replace XXXX with the RFC number of this
document.
9. 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 when a call is diverted , it is
important to ensure that the parameter has not been added to the SIP
message by an unauthorized SIP entity. Thus, the P-Served-User
header field is to be used in a trusted environment and proxies MUST
NOT insert the header unless they have sufficient knowledge that the
route set includes another trusted proxy.
Mohali Expires June 13, 2019 [Page 12]
Internet-Draft P-Served-User parameter orig-cdiv December 2018
10. Acknowledgments
The author wishes to thank the 3GPP community for providing guidance,
input, and comments on the document. Thanks to Dale Worley, Jean
Mahoney and Ben Campbell for their careful review of the document.
Thanks to Paul Kyzivat and Adam Roach. A special thanks to Christer
Holmberg.
11. References
11.1. 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,
<https://www.rfc-editor.org/info/rfc2119>.
[RFC3324] Watson, M., "Short Term Requirements for Network Asserted
Identity", RFC 3324, DOI 10.17487/RFC3324, November 2002,
<https://www.rfc-editor.org/info/rfc3324>.
[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>.
[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>.
[RFC8217] Sparks, R., "Clarifications for When to Use the name-addr
Production in SIP Messages", RFC 8217,
DOI 10.17487/RFC8217, August 2017,
<https://www.rfc-editor.org/info/rfc8217>.
[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>.
Mohali Expires June 13, 2019 [Page 13]
Internet-Draft P-Served-User parameter orig-cdiv December 2018
[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>.
[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>.
11.2. Informative References
[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
Marianne Mohali
Orange
Orange Gardens, 44 avenue de la Republique
Chatillon 92326
France
Email: marianne.mohali@orange.com
Mohali Expires June 13, 2019 [Page 14]
