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<!DOCTYPE rfc [
  <!ENTITY nbsp    "&#160;">
  <!ENTITY zwsp   "&#8203;">
  <!ENTITY nbhy   "&#8209;">
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<rfc xmlns:xi="http://www.w3.org/2001/XInclude" category="info" ipr="trust200902" updates="7315" docName="draft-ietf-sipcore-rfc7976bis-04" number="9878" consensus="true" obsoletes="7976" submissionType="IETF" xml:lang="en" tocInclude="true" tocDepth="4" symRefs="true" sortRefs="true" version="3">

<!-- xml2rfc v2v3 conversion 3.17.3 [rfced] Because this document updates RFC 7315, please
review the errata reported for RFC 7315
(https://www.rfc-editor.org/errata/rfc7315)
and let us know if you confirm our opinion that none of them
are relevant to the content of this document.
-->

<!-- [rfced] Because this document obsoletes RFC 7976, please
review the errata reported for RFC 7976
(https://www.rfc-editor.org/errata/rfc7976)
and let us know if you confirm our opinion that none of them
are relevant to the content of this document.
-->

  <front>
    <title abbrev="Update to Private Header">Updates to Private Header (P-Header) Extension Usage
      in Session Initiation Protocol (SIP) Requests and Responses</title>
    <seriesInfo name="Internet-Draft" value="draft-ietf-sipcore-rfc7976bis-04"/> name="RFC" value="9878"/>
    <author initials="C." surname="Holmberg" fullname="Christer Holmberg">
      <organization>Ericsson</organization>
      <address>
        <postal>
          <street>Hirsalantie 11</street>
          <city>Jorvas</city>
          <code>02420</code>
          <country>Finland</country>
        </postal>        <phone/>
        <email>christer.holmberg@ericsson.com</email>        <uri/>
      </address>
    </author>
    <author initials="N." surname="Biondic" fullname="Nevenka Biondic">
      <organization>Ericsson</organization>
      <address>
        <postal>
          <street>Krapinska 45</street>
          <city>Zagreb</city>
          <code>10002</code>
          <country>Croatia</country>
        </postal>        <phone/>
        <email>nevenka.biondic.ext@ericsson.com</email>        <uri/>
      </address>
    </author>
    <author initials="G." surname="Salgueiro" fullname="Gonzalo Salgueiro">
      <organization>Cisco Systems, Inc.</organization>
      <address>
        <postal>
          <street>7200-12 Kit Creek Road</street>
          <city>Research Triangle Park</city>          <code>NC  27709</code>
          <region>NC</region><code>27709</code>
          <country>United States of America</country>
        </postal>        <phone/>
        <email>gsalguei@cisco.com</email>        <uri/>
      </address>
    </author>
    <author initials="R." surname="Jesske" fullname="Roland Jesske">
      <organization>Deutsche Telekom</organization>
      <address>
        <postal>
          <street>Telekom Allee 9</street>
          <city>Darmstadt</city>
          <code>64295</code>
          <country>Germany</country>
        </postal>        <phone/>
        <email>r.jesske@telekom.de</email>
        <uri>www.telekom.com</uri>
      </address>
    </author>
    <date year="2025"/> year="2025" month="October"/>
    <area>ART</area>
    <workgroup>sipcore</workgroup>    <keyword>Internet-Draft</keyword>

    <keyword>3GPP</keyword>
    <keyword>Visited</keyword>
    <keyword>ID</keyword>

    <abstract>
      <t>
<!--[rfced] Abstract and Introduction: Please review if the first sentence
conveys the intended meaning. Specifically, should "currently not allowed"
be rephrased? This text is directly from RFC 7976, published in 2016. What
is the subject of "not allowed"? It can be read as the requests and responses
are not allowed.

Based on "This specification allows some header fields to be present
in messages where they were previously not allowed" (Section 5),
we make the following suggestion.

Original:
   The Third Generation Partnership Project (3GPP) has identified cases
   where different SIP private header extensions referred to as "P-"
   header fields, and defined in RFC 7315, need to be included in SIP
   requests and responses currently not allowed according to RFC 7315.

Perhaps:
   The Third Generation Partnership Project (3GPP) has identified cases
   where different SIP private header extensions referred to as "P-"
   header fields, and defined in RFC 7315, need to be included in SIP
   requests and responses where they were not allowed according to RFC 7315.
-->
   The Third Generation Partnership Project (3GPP) has identified cases where different SIP private header extensions referred to as "P-" header fields, and defined in RFC 7315, need to be included in SIP requests and responses currently not allowed according to RFC 7315. This document updates RFC 7315, in order to allow inclusion of the affected "P-" header fields in such requests and responses. This Document document obsoletes RFC 7976. The changes related to RFC7976 RFC 7976 involve the inclusion of the P-Visited-Network-ID header
     field in SIP responses.</t><t> responses.
</t>
<!--[rfced] Abstract and Introduction: Please clarify "when RFC 3455 was
updated and subsequently obsoleted by the publication of RFC 7315".

In the RFC series, "updated" has a specific meaning, distinct from "obsoleted".
RFC 3455 has not been updated by any other RFCs, so the original sentence
is not accurate. We suggest simply "obsoleted" as follows. Please let us
know if you prefer otherwise.

Original:
   This document also makes updates for RFC 7315 in order to fix
   misalignments that occurred when RFC 3455 was updated and
   subsequently obsoleted by the publication of RFC 7315.

Perhaps:
   This document also makes updates for RFC 7315 in order to fix
   misalignments that occurred when RFC 3455 was obsoleted by
   RFC 7315.

Or (if you prefer to explain):
   This document also makes updates for RFC 7315 in order to fix
   misalignments that occurred when RFC 3455 was obsoleted by
   RFC 7315, i.e., when the content of RFC 3455 was completely replaced.
-->
<t>
   This document also makes updates to RFC 7315 in order to fix misalignments that occurred when RFC 3455 was updated and subsequently obsoleted by the publication of RFC 7315.
      </t>
    </abstract>
  </front>
  <middle>    <!-- ***************************************************************************************************** -->

    <section anchor="intro" numbered="true" toc="default">
      <name>Introduction</name>
      <t>
	   The Third Generation Partnership Project (3GPP) has identified cases where different Session Initiation Protocol (SIP) <xref target="RFC3261" format="default"/> private header extensions
	   referred to 		as "P-" header fields, and defined in <xref target="RFC7315" format="default"/>, need to be included in SIP requests and responses
	   currently not allowed according to <xref target="RFC7315" format="default"/>.  This document updates <xref target="RFC7315" format="default"/>, in order to allow inclusion of the affected "P-" header
	   fields in such requests and responses.	</t><t>
	</t>
<t>
	   This document also makes updates for to <xref target="RFC7315" format="default"/> in order to fix
	   misalignments that occurred when <xref target="RFC3455" format="default"/> was updated and subsequently obsoleted by the publication of <xref target="RFC7315" format="default"/>.

      </t>
    </section>
    <section anchor="Misalingment_3GPP_Use_Cases" anchor="Misalignment_3GPP_Use_Cases" numbered="true" toc="default">
      <name>Misalignments and 3GPP Use Cases</name>
      <section anchor="General" numbered="true" toc="default">
        <name>General</name>
        <t>
										  <xref target="RFC7315" format="default"/> contains contradicting contradictory statements regarding the usage of SIP
					   "P-" header fields in SIP requests and responses, which leave the presence of the SIP "P-" header fields in the SIP requests and
					   responses open to interpretation and different implementations. Statements in Section 5.7 of that RFC <xref target="RFC7315" section="5.7"/> are not aligned with the
					   definitions and usage of the SIP "P-" header fields specified in Section 4. <xref target="RFC7315" section="4"/>.  This section describes the misalignments that occurred
					   when <xref target="RFC3455" format="default"/> was updated and subsequently obsoleted by the publication of <xref target="RFC7315" format="default"/>, and how they are fixed.
        </t>
<!-- [rfced] Would you like the note in this document to be in an
<aside> element, or remain as is? It is defined as "a container for
content that is semantically less important or tangential to the
content that surrounds it" (https://authors.ietf.org/rfcxml-vocabulary#aside).

Original:
   NOTE: In the case of the P-Called-Party-ID header field, allowing it
   in PUBLISH requests was done deliberately in [RFC7315].  Therefore,
   it is not considered a misalignment.
-->

        <t>
					   NOTE: In the case of the P-Called-Party-ID header field, allowing it
					   in PUBLISH requests was done deliberately in <xref target="RFC7315" format="default"/>.  Therefore, it
					   is not considered a misalignment.
        </t>
        <t>
					   Since <xref target="RFC7315" format="default"/> was published, 3GPP defined new use cases that require
					   the RFC to be updated.  This section describes the 3GPP use cases
					   behind the updates, and the updates needed to <xref target="RFC7315" format="default"/> in order to
					   support the use cases.
        </t>

        <t> 					   Section 3
					   <xref target="Updates_to_RFC_7315"/> updates <xref target="RFC7315" format="default"/>, based on the misalignments and 3GPP use
					   cases.

        </t>
      </section>
      <section anchor="Misalignments" numbered="true" toc="default">
        <name>Misalignments</name>
        <t>
						 The following updates are needed in order to fix the misalignments
						   that occurred when <xref target="RFC3455" format="default"/> was updated and obsolated obsoleted by <xref target="RFC7315" format="default"/>:
        </t>        <t>						   o  P-Associated-URI:

<ul spacing="normal">
<li>P-Associated-URI: Remove the statement that the header field can appear in
the SIP REGISTER method.        </t>        <t>						   o  P-Called-Party-ID: method.</li>
<li>P-Called-Party-ID: Delete the statement that the P-Called-Party-ID header
field can appear in SIP responses.  Add a statement that the P-Called-Party-ID
header field can appear in the SIP REFER							  method.        </t>                <t>							   o  P-Access-Network-Info: method.</li>
<li>P-Access-Network-Info: Add a statement that the P-Access-Network- Info
header field can appear in SIP responses.        </t>        <t>						   o  P-Charging-Vector: responses.</li>
<li>P-Charging-Vector: Add a statement that the P-Charging-Vector header field
can appear in SIP responses.  Add a statement that the P-Charging-Vector
header field cannot appear in the SIP ACK							  method.        </t>        <t>						   o  P-Charging-Function-Addresses: method.</li>
<li>P-Charging-Function-Addresses: Add a statement that the
P-Charging-Function-Addresses header field can appear in SIP							  responses.        </t>        <t>  						 The responses.</li>
</ul>

        <t>The following update is needed in order to clarify the usage of
        the header compared to <xref target="RFC7315" format="default"/>:        </t>        <t>						   o  P-Visited-Network-ID: format="default"/>:</t>
<ul spacing="normal">
<li>P-Visited-Network-ID: Add a statement that the P-Visited-Network-ID header
field cannot appear in the SIP NOTIFY, PRACK, INFO, and UPDATE methods. Add
statement that the P-Visited-Network-ID header field can appear in all non-100
(Trying) responses.		 </t> responses.</li>
</ul>
      </section>      <!-- ***************************************************************************************************** -->

      <section anchor="_GPP_Use_Cases" numbered="true" toc="default">
        <name>3GPP Use Cases</name>        <!-- ***************************************************************************************************** -->

	<section anchor="General_use_case" numbered="true" toc="default">
          <name>General</name>          <t>  								   The
          <t>The following updates are needed in order to implement the 3GPP
          use									   cases:          </t>          <t> 									   o  P-Access-Network-Info: cases:</t>

<ul spacing="normal">
  <li>P-Access-Network-Info: Add statement that the P-Access-Network- Info
  header field can appear in the SIP ACK method when triggered by a SIP 2xx response.          </t>          <t>									   o  P-Charging-Vector:
  response.</li>
  <li>P-Charging-Vector: Add statement that the P-Charging-Vector header field
  can appear in the SIP ACK method when triggered by a SIP 2xx										  response.          </t>          <t>									   This response.</li>
</ul>

  <t>This following sections describe, for individual "P-" header fields, the
  3GPP use cases that are the basis for the updates.  The use cases are based
  on the procedures defined in <xref target="TS24.229" format="default"/>.          </t> format="default"/>.</t>
        </section>        <!-- ***************************************************************************************************** -->

	<section anchor="P-Access-Network-Info" numbered="true" toc="default">
          <name>P-Access-Network-Info</name>
          <t>

								   The P-Access-Network-Info header field may contain the Network
								   Provided Location Information (NPLI).  The NPLI is described in
								   <xref target="TS23.228" format="default"/>.

          </t>
          <t>
								   A proxy in possession of appropriate information about the access
								   technology might insert a P-Access-Network-Info header field with its
								   own values.  Such values are identified by the string "network-
								   provided" defined in <xref target="RFC7315" format="default"/>.  Based on operator policy, roaming agreement agreement, or both, the local time of the visited network may be
								   included.
          </t>          <t>								     The
<!--[rfced] To prevent misreading this sentence (i.e., "the NPLI needs to
be stored as the location of the user"), may we add a comma as follows?

Original:
   When an IMS session is modified, the NPLI also
   needs to be stored as the location of the user at the time when the
   session is modified may generate a charging event.

Suggested:
   When an IMS session is modified, the NPLI also
   needs to be stored, as the location of the user at the time when the
   session is modified may generate a charging event.
-->
          <t>The Call Data Records (CDRs) generated within the IP Multimedia
          Subsystem (IMS) have to contain the NPLI in order to guarantee
          correct billing.  When an IMS session is modified, the NPLI also
          needs to be stored as the location of the user at the time when the
          session is modified may generate a charging event.  In case of a
          session modification event at IMS, the NPLI needs to be provided:          </t>          <t>								    o  when provided:</t>

<ul spacing="normal">
  <li>when the bearer establishment is triggered, or          </t>          <t>									   o  at or</li>
  <li>at session release when the bearer deactivation is triggered, or          </t>          <t>									   o  when or</li>
  <li>when the bearer modification is triggered, e.g., a QoS modification for
  the use of a newly negotiated codec.          </t> codec.</li>
</ul>
<!--[rfced] We suggest adding articles ('the' and 'a') as follows; please let
us know if this is acceptable. (We note that RFC 7976 did not use
articles in similar text, but 'a SIP 2xx response' appears in other RFCs.)

Original: ... within SIP 2xx response to the SIP INVITE request.
Perhaps:  ... within the SIP 2xx response to the SIP INVITE request.

Original: Upon reception of the SDP answer within SIP 2xx response ..
Perhaps:  Upon reception of the SDP answer within a SIP 2xx response ...
-->
          <t>
									   In some scenarios, the bearer modification may be triggered by the
									   proxy upon reception of a Session Description Protocol (SDP) answer
									   within SIP 2xx response to the SIP INVITE request.  In such case, the
									   NPLI needs to be provided within the SIP ACK request.  However, <xref target="RFC7315" format="default"/>  does not allow the usage of the P-Access-Network-Info header
									   field in a SIP ACK request.
          </t>
          <t>
									   Upon reception of the SDP answer within SIP 2xx response on the SIP
									   INVITE request, a proxy may initiate procedures to obtain the NPLI
									   and may include the P-Access-Network-Info header field with the NPLI
									   in the SIP ACK request.
          </t>
          <t>
									   The P-Access-Network-Info header field shall not be included in SIP
									   ACK requests triggered by non-2xx responses.
          </t>
        </section>        <!-- ***************************************************************************************************** --> 								 <!-- ***************************************************************************************************** -->

	<section anchor="P-Charging-Vector" numbered="true" toc="default">
          <name>P-Charging-Vector</name>
          <t>

								   <xref target="RFC7315" format="default"/> defines an Inter Operator Identifier (IOI) to enable
								   different operators involved in a SIP dialog or a transaction outside
								   a dialog to identify each other by exchanging operator identification
								   information within the P-Charging-Vector header field.
          </t>
          <t>
								   In the interconnection scenarios in multi-operator environments,
								   where one or more transit operators are between the originating and
								   terminating operator, the identities of the involved transit
								   operators are represented by a transit-ioi parameter of the
								   P-Charging-Vector header field.
          </t>
          <t>
								   Transit operators can be selected independently for each SIP method
								   and direction of request.  A transit network will only have knowledge
								   of an individual SIP request, and transit network selection will be
								   an independent decision for each request and could be made based on
								   load, cost, percentage, time of day, and other factors.  For this
								   reason, it is necessary that the P-Charging-Vector header field,
								   which carries the transit IOI information, is included in each SIP
								   request and response.  However, <xref target="RFC7315" format="default"/> does not allow the usage of
								   the P-Charging-Vector header field in the SIP ACK request.
								    </t>
          <t>
								    A SIP proxy that supports this extension and receives the SIP ACK
								   request may include a P-Charging-Vector header field in the SIP ACK
								   request.
          </t>
<!--[rfced] non-2xx response vs. SIP non-2xx respsonse
In other instances in this document, "SIP" does not appear before
"non-2xx repsonse"; may it be removed here, or is it necessary?

Original:
   The P-Charging-Vector header field shall not be included in SIP ACK
   requests triggered by SIP non-2xx responses.

Perhaps (to match usage in Sections 2.3.2 and 3):
   The P-Charging-Vector header field shall not be included in SIP ACK
   requests triggered by non-2xx responses.
-->
          <t>
								   The P-Charging-Vector header field shall not be included in SIP ACK
								   requests triggered by SIP non-2xx responses.

          </t>
        </section>        <!-- ***************************************************************************************************** -->
      </section>
    </section>    <!-- ********************************************************************************************************************************************************** -->
   <section anchor="Updates_to_RFC_7315" numbered="true" toc="default">
      <name>Updates to RFC 7315</name>
      <t>

	   This section implements contains the update to Section 5.7 of <xref target="RFC7315" format="default"/>, section="5.7"/>, in
	   order to implement the misalignment fixes and the 3GPP requirements
	   described in Section 2.      </t>      <t>	   Old text: <xref target="Misalignment_3GPP_Use_Cases"/>.
      </t>
<!--[rfced] FYI, in Section 3, the quote of RFC 7315 ("Old text") has
been updated to exactly match the RFC. If you prefer to keep the blank
lines between each sentence, then please let us know and we would suggest
adding text to note that it does not match the original, e.g., "Blank
lines have been added for readability."
-->
<t>Old text:</t>
<blockquote>
      <t>
The P-Associated-URI header field can appear in SIP REGISTER method
and 2xx resonses.	   </t>       <t> resonses [sic].  The P-Called-Party-ID header field can appear in
SIP INVITE, OPTIONS, PUBLISH, SUBSCRIBE, and MESSAGE methods and all
responses.	   </t>      <t>  The P-Visited-Network-ID header field can appear in all
SIP methods except ACK, BYE, and CANCEL and all responses.	   </t>      <t>The  The
P-Access-Network-Info header field can appear in all SIP methods
except ACK and CANCEL.	   </t>       <t>The  The P-Charging-Vector header field can appear
in all SIP methods except CANCEL.	   </t>      <t>The  The P-Charging-Function-Addresses
header field can appear in all SIP methods except ACK and CANCEL.
      </t>      <t>	   New text:      </t>            <t>	   The
</blockquote>

      <t>New text:</t>

<blockquote>
      <t>The P-Associated-URI header field can appear in SIP REGISTER 2xx
      responses.
      </t>
      <t>
       The P-Called-Party-ID header field can appear in the SIP INVITE,
       OPTIONS, PUBLISH, REFER, SUBSCRIBE, and MESSAGE requests.
      </t>
      <t>
	The P-Visited-Network-ID header field can appear in all SIP requests
	and the associated non-100 response message except in ACK, BYE,
	CANCEL, NOTIFY, PRACK, INFO, UPDATE.
      </t>
      <t>
       The P-Access-Network-Info header field can appear in all SIP requests
       and the associated non-100 responses, except in CANCEL requests, CANCEL
       responses, and ACK methods triggered by non-2xx responses.
      </t>
      <t>
	The P-Charging-Vector header field can appear in all SIP requests and
	the associated non-100 responses, except in CANCEL requests, CANCEL
	responses, and ACK requests triggered by non-2xx responses.
      </t>
      <t>
       The P-Charging-Function-Addresses header field can appear in all SIP
       methods and the associated non-100 responses, except in CANCEL
       requests, CANCEL responses, and ACK requests.
      </t>
</blockquote>
    </section>    <!-- ********************************************************************************************************************************************************* -->

    <section anchor="IANA" numbered="true" toc="default">
      <name>IANA Considerations</name>
	  <t>	  No
	  This document has no IANA Considerations. actions.
	  </t>
    </section>

    <section anchor="security" numbered="true" toc="default">
      <name>Security Considerations</name>
      <t>
   The security considerations for these "P-" header fields are defined
   in <xref target="RFC7315" format="default"/>.  This specification allows some header fields to be
   present in messages where they were previously not allowed, and the
   security considerations and assumptions described in <xref target="RFC7315" format="default"/> (e.g.,
   regarding only sending information to trusted entities) also apply to
   those messages.
   In addition, this specification also disallows some
   header fields to be present in messages where they were previously
   allowed.  That does not cause any security issues, but implementors
   need to be aware that implementations may not have been updated
   according to this document, and take proper actions if a header field
   occurs, or does not occur, in a message where it should occur (or
   occurs in a message where it should not occur).
   This document adds
   the ability to include P-Access-Network-Info in ACK requests.  As
   documented in <xref target="RFC7315" format="default"/>, P-Access-Network-Info may include privacy
   sensitive information, including the user's location.  The security
   and privacy considerations for P-Access-Network-Info in ACK requests
   are similar to those for the other SIP requests discussed in Section 6.4 of
   <xref target="RFC7315" format="default"/>. section="6.4"/>.
   The security and privacy considerations for  the P-Visited-Network-ID header field are
   similar to those for the other SIP responses discussed in Section 6.3 of <xref target="RFC7315" format="default"/>. section="6.3"/>.

      </t>
    </section>    <!-- ***************************************************************************************************** -->

    <section numbered="true" toc="default">
      <name>Operational considerations</name>
      <t>
      	   As the "P-" header fields are mainly used in (and in most cases, only defined for)
      	   networks defined by the 3GPP, where the updates defined in this document are already
	   defined  <xref target="TS24.229" format="default"/>, the updates are not seen to cause
	   backward-compatibility concerns.

           </t>    </section><!-- ***************************************************************************************************** -->  <!-- ***************************************************************************************************** -->
    </section>

    <section numbered="true" toc="default">
      <name>Changes since RFC7976</name> RFC 7976</name> <t> The changes related to RFC7976 RFC 7976
      involve the inclusion of the P-Visited-Network-ID header field in SIP
      responses. Specifically, any SIP response message, with the exception of
      a 100 (Trying) response, may include a P-Visited-Network-ID header
      field.

      </t>    </section><!-- ***************************************************************************************************** -->
    </section>

    <section numbered="true" toc="default">
      <name>Acknowledgments</name>      <t>      The
   <t>The author would like to acknowledge the constructive feedback provided
   by Michael Kreipl, Charles Eckel and Paul Kyzivat      Thanks to Paul Kyzivat, Jean Mahoney, Ben Campbell, and Adam Roach <contact fullname="Michael Kreipl"/>, <contact fullname="Charles
   Eckel"/>, and <contact fullname="Paul Kyzivat"/>.</t>
   <t>Thanks to <contact fullname="Paul Kyzivat"/>, <contact fullname="Jean
   Mahoney"/>, <contact fullname="Ben Campbell"/>, and <contact fullname="Adam
   Roach"/> for providing comments on the former an earlier draft version of the this document.
      </t>
    </section>
  </middle>
  <back>
    <references>
      <name>References</name>
      <references>

        <name>Normative References</name>        <reference anchor="RFC3261" target="https://www.rfc-editor.org/info/rfc3261">           <front>            <title>SIP: Session Initiation Protocol</title>            <author fullname="J. Rosenberg" initials="J." surname="Rosenberg"/>            <author fullname="H. Schulzrinne" initials="H." surname="Schulzrinne"/>            <author fullname="G. Camarillo" initials="G." surname="Camarillo"/>            <author fullname="A. Johnston" initials="A." surname="Johnston"/>            <author fullname="J. Peterson" initials="J." surname="Peterson"/>            <author fullname="R. Sparks" initials="R." surname="Sparks"/>            <author fullname="M. Handley" initials="M." surname="Handley"/>            <author fullname="E. Schooler" initials="E." surname="Schooler"/>            <date month="June" year="2002"/>            <abstract>              <t>This document describes Session Initiation Protocol (SIP), an application-layer control (signaling) protocol for creating, modifying, and terminating sessions with one or more participants.  These sessions include Internet telephone calls, multimedia distribution, and multimedia conferences. [STANDARDS-TRACK]</t>            </abstract>          </front>          <seriesInfo name="RFC" value="3261"/>          <seriesInfo name="DOI" value="10.17487/RFC3261"/>        </reference>        <reference anchor="RFC7315" target="https://www.rfc-editor.org/info/rfc7315">           <front>            <title>Private Header (P-Header) Extensions to

        <xi:include href="https://bib.ietf.org/public/rfc/bibxml/reference.RFC.3261.xml"/>
        <xi:include href="https://bib.ietf.org/public/rfc/bibxml/reference.RFC.7315.xml"/>

<!-- [rfced] FYI, we updated the Session Initiation Protocol (SIP) for 3GPP reference titles to match
the 3GPP</title>            <author fullname="R. Jesske" initials="R." surname="Jesske"/>            <author fullname="K. Drage" initials="K." surname="Drage"/>            <author fullname="C. Holmberg" initials="C." surname="Holmberg"/>            <date month="July" year="2014"/>            <abstract>              <t>This document describes a set of private header (P-header) Session Initiation Protocol (SIP) fields used titles provided by the 3GPP, along with their applicability, which is limited 3GPP. We have also added URLs that point to particular environments.  The P-header fields are
the specific version used for a variety of purposes within in the networks that references. Please review.

We note the partners implement, including charging version referenced in this document is from 2016 and information about there have
been several updates over the networks years. Would you like to update this
reference to a call traverses.  This document obsoletes RFC 3455.</t>            </abstract>          </front>          <seriesInfo name="RFC" value="7315"/>          <seriesInfo name="DOI" value="10.17487/RFC7315"/>        </reference>        <reference anchor="TS23.228">          <front>            <title>3rd Generation Partnership Project; more current version? Or would you like these
references to point to the 3GPP Technical Specification Group Core Network Specifications in general?

Current:
   [TS23.228] 3GPP, "IP Multimedia Subsystem (IMS); Stage 2", Version
              13.6.0, Release 13, 3GPP TS 23.228, June 2016,
              <https://www.3gpp.org/ftp//Specs/
              archive/23_series/23.228/23228-g30.zip>.

   [TS24.229] 3GPP, "IP multimedia call control protocol based on
              Session Initiation Protocol (SIP) and Terminals; Session Description
              Protocol (SDP); Stage 3", Version 13.6.0, Release 13, 3GPP
              TS 24.229, June 2016, <https://www.3gpp.org/ftp/Specs/
              archive/24_series/24.229/24229-d60.zip>.

Perhaps:
   [TS23.228]
              3GPP, "IP Multimedia Subsystem (IMS); Stage 2", 3GPP
              TS 23.228,
              <https://portal.3gpp.org/desktopmodules/Specifications/
              SpecificationDetails.aspx?specificationId=821>.

   [TS24.229]
              3GPP, "IP multimedia call control protocol based on
              Session Initiation Protocol (SIP) and Session Description
              Protocol (SDP); Stage 3", 3GPP TS 24.229,
              <https://portal.3gpp.org/desktopmodules/Specifications/
              SpecificationDetails.aspx?specificationId=1055>.
-->
        <reference anchor="TS23.228" target="https://www.3gpp.org/ftp//Specs/archive/23_series/23.228/23228-g30.zip">
          <front>
            <title>IP Multimedia Subsystem (IMS); Stage 2

            </title>
            <author>
              <organization abbrev="3GPP">
                   3rd Generation Partnership Project
              </organization>
            </author>
            <date month="June" year="2016"/>
          </front>
          <seriesInfo name="TS" name="3GPP TS" value="23.228"/>          <seriesInfo name="V" value="13.6.0"/>
          <refcontent>Version 13.6.0, Release 13</refcontent>
        </reference>

<!--[options, dependent on author reply]
General version of 3GPP references (if authors want to go with these)
        <reference anchor="TS24.229"> anchor="TS23.228" target="https://portal.3gpp.org/desktopmodules/Specifications/SpecificationDetails.aspx?specificationId=821">
          <front>            <title>3rd
            <title>IP Multimedia Subsystem (IMS); Stage 2

            </title>
            <author>
              <organization abbrev="3GPP">
                   3rd Generation Partnership Project;				Technical Specification Group Core Network and Terminals;				IP Project
              </organization>
            </author>
          </front>
          <seriesInfo name="3GPP TS" value="23.228"/>
        </reference>

        <reference anchor="TS24.229" target="https://portal.3gpp.org/desktopmodules/Specifications/SpecificationDetails.aspx?specificationId=1055">
          <front>
            <title>IP multimedia call control protocol based on Session Initiation Protocol (SIP) and Session Description Protocol (SDP); Stage 3
            </title>
            <author>
              <organization abbrev="3GPP">
                   3rd Generation Partnership Project
              </organization>
            </author>            <date month="June" year="2016"/>
          </front>
          <seriesInfo name="TS" name="3GPP TS" value="24.229"/>          <seriesInfo name="V" value="13.6.0"/>
        </reference>      </references>      <references>      <name>Informative References</name>
-->
        <reference anchor="RFC3455" target="https://www.rfc-editor.org/info/rfc3455"> anchor="TS24.229" target="https://www.3gpp.org/ftp/Specs/archive/24_series/24.229/24229-d60.zip">
          <front>            <title>Private Header (P-Header) Extensions to the
            <title>IP multimedia call control protocol based on Session Initiation Protocol (SIP) for the 3rd-Generation Partnership Project (3GPP)</title>            <author fullname="M. Garcia-Martin" initials="M." surname="Garcia-Martin"/>            <author fullname="E. Henrikson" initials="E." surname="Henrikson"/>            <author fullname="D. Mills" initials="D." surname="Mills"/>            <date month="January" year="2003"/>            <abstract>              <t>This document describes a set of private and Session Initiation Description Protocol (SIP) headers (P-headers) used by the 3rd-Generation (SDP); Stage 3
            </title>
            <author>
              <organization abbrev="3GPP">
                   3rd Generation Partnership Project (3GPP), along with their applicability, which is limited to particular environments.  The P-headers are for a variety of purposes within the networks that the partners use, including charging and information about the networks a call traverses.  This memo provides information for the Internet community.</t>            </abstract>
              </organization>
            </author>
            <date month="June" year="2016"/>
          </front>
          <seriesInfo name="RFC" value="3455"/>          <seriesInfo name="DOI" value="10.17487/RFC3455"/> name="3GPP TS" value="24.229"/>
          <refcontent>Version 13.6.0, Release 13</refcontent>
        </reference>

      </references>

      <references>
      <name>Informative References</name>
        <xi:include href="https://bib.ietf.org/public/rfc/bibxml/reference.RFC.3455.xml"/>
      </references>

    </references>  </back></rfc>

  </back>

<!-- [rfced] Please review the "Inclusive Language" portion of the online
Style Guide <https://www.rfc-editor.org/styleguide/part2/#inclusive_language>
and let us know if any changes are needed.  Updates of this nature typically
result in more precise language, which is helpful for readers.

Note that our script did not flag any words in particular, but this should
still be reviewed as a best practice.
-->

</rfc>