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<pre>Internet Engineering Task Force (IETF) C. Holmberg
Request for Comments: 8262 I. Sedlacek
Updates: <a href="./rfc5368">5368</a>, <a href="./rfc5621">5621</a>, <a href="./rfc6442">6442</a> Ericsson
Category: Standards Track October 2017
ISSN: 2070-1721
<span class="h1">Content-ID Header Field in the Session Initiation Protocol (SIP)</span>
Abstract
This document specifies the Content-ID header field for usage in the
Session Initiation Protocol (SIP). This document also updates <a href="./rfc5621">RFC</a>
<a href="./rfc5621">5621</a>, which only allows a Content-ID URL to reference a body part
that is part of a multipart message-body. This update enables a
Content-ID URL to reference a complete message-body and metadata
provided by some additional SIP header fields.
This document updates <a href="./rfc5368">RFC 5368</a> and <a href="./rfc6442">RFC 6442</a> by clarifying their usage
of the SIP Content-ID header field.
Status of This Memo
This is an Internet Standards Track document.
This document is a product of the Internet Engineering Task Force
(IETF). It represents the consensus of the IETF community. It has
received public review and has been approved for publication by the
Internet Engineering Steering Group (IESG). Further information on
Internet Standards is available in <a href="./rfc7841#section-2">Section 2 of RFC 7841</a>.
Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
<a href="https://www.rfc-editor.org/info/rfc8262">https://www.rfc-editor.org/info/rfc8262</a>.
<span class="grey">Holmberg & Sedlacek Standards Track [Page 1]</span></pre>
<hr class='noprint'/><!--NewPage--><pre class='newpage'><span id="page-2" ></span>
<span class="grey"><a href="./rfc8262">RFC 8262</a> Content-ID in SIP October 2017</span>
Copyright Notice
Copyright (c) 2017 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to <a href="https://www.rfc-editor.org/bcp/bcp78">BCP 78</a> and the IETF Trust's Legal
Provisions Relating to IETF Documents
(<a href="https://trustee.ietf.org/license-info">https://trustee.ietf.org/license-info</a>) 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
<a href="#section-1">1</a>. Introduction . . . . . . . . . . . . . . . . . . . . . . . . <a href="#page-3">3</a>
<a href="#section-1.1">1.1</a>. Identifying a Body Part . . . . . . . . . . . . . . . . . <a href="#page-3">3</a>
<a href="#section-1.2">1.2</a>. Referencing a Body Part . . . . . . . . . . . . . . . . . <a href="#page-3">3</a>
<a href="#section-1.3">1.3</a>. Problem Statement . . . . . . . . . . . . . . . . . . . . <a href="#page-4">4</a>
<a href="#section-1.4">1.4</a>. Consequences . . . . . . . . . . . . . . . . . . . . . . <a href="#page-4">4</a>
<a href="#section-1.4.1">1.4.1</a>. Example 1: SIP INVITE . . . . . . . . . . . . . . . . <a href="#page-4">4</a>
<a href="#section-1.4.2">1.4.2</a>. Example 2: SIP REFER . . . . . . . . . . . . . . . . <a href="#page-6">6</a>
<a href="#section-1.5">1.5</a>. Solution . . . . . . . . . . . . . . . . . . . . . . . . <a href="#page-7">7</a>
<a href="#section-1.6">1.6</a>. Backward Compatibility . . . . . . . . . . . . . . . . . <a href="#page-7">7</a>
<a href="#section-2">2</a>. Conventions . . . . . . . . . . . . . . . . . . . . . . . . . <a href="#page-7">7</a>
<a href="#section-3">3</a>. Content-ID Header Field . . . . . . . . . . . . . . . . . . . <a href="#page-8">8</a>
<a href="#section-3.1">3.1</a>. Introduction . . . . . . . . . . . . . . . . . . . . . . <a href="#page-8">8</a>
<a href="#section-3.2">3.2</a>. Syntax . . . . . . . . . . . . . . . . . . . . . . . . . <a href="#page-8">8</a>
<a href="#section-3.3">3.3</a>. Semantics . . . . . . . . . . . . . . . . . . . . . . . . <a href="#page-8">8</a>
<a href="#section-3.4">3.4</a>. Procedures . . . . . . . . . . . . . . . . . . . . . . . <a href="#page-9">9</a>
<a href="#section-3.4.1">3.4.1</a>. User Agent (UA) Procedures . . . . . . . . . . . . . <a href="#page-9">9</a>
<a href="#section-3.4.2">3.4.2</a>. Proxy Procedures . . . . . . . . . . . . . . . . . . <a href="#page-9">9</a>
3.4.3. Example: Referencing the Message-Body of a SIP
Message . . . . . . . . . . . . . . . . . . . . . . . <a href="#page-9">9</a>
<a href="#section-4">4</a>. Update to <a href="./rfc5368">RFC 5368</a> . . . . . . . . . . . . . . . . . . . . . <a href="#page-10">10</a>
<a href="#section-5">5</a>. Update to <a href="./rfc5621">RFC 5621</a> . . . . . . . . . . . . . . . . . . . . . <a href="#page-11">11</a>
<a href="#section-6">6</a>. Update to <a href="./rfc6442">RFC 6442</a> . . . . . . . . . . . . . . . . . . . . . <a href="#page-11">11</a>
<a href="#section-7">7</a>. Security Considerations . . . . . . . . . . . . . . . . . . . <a href="#page-12">12</a>
<a href="#section-8">8</a>. IANA Considerations . . . . . . . . . . . . . . . . . . . . . <a href="#page-12">12</a>
<a href="#section-8.1">8.1</a>. Header Field . . . . . . . . . . . . . . . . . . . . . . <a href="#page-12">12</a>
<a href="#section-9">9</a>. References . . . . . . . . . . . . . . . . . . . . . . . . . <a href="#page-13">13</a>
<a href="#section-9.1">9.1</a>. Normative References . . . . . . . . . . . . . . . . . . <a href="#page-13">13</a>
<a href="#section-9.2">9.2</a>. Informative References . . . . . . . . . . . . . . . . . <a href="#page-14">14</a>
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . <a href="#page-14">14</a>
<span class="grey">Holmberg & Sedlacek Standards Track [Page 2]</span></pre>
<hr class='noprint'/><!--NewPage--><pre class='newpage'><span id="page-3" ></span>
<span class="grey"><a href="./rfc8262">RFC 8262</a> Content-ID in SIP October 2017</span>
<span class="h2"><a class="selflink" id="section-1" href="#section-1">1</a>. Introduction</span>
<span class="h3"><a class="selflink" id="section-1.1" href="#section-1.1">1.1</a>. Identifying a Body Part</span>
A SIP message consists of a start-line, one or more header fields, an
empty line indicating the end of the header fields, and an optional
message-body as specified in [<a href="./rfc3261" title=""SIP: Session Initiation Protocol"">RFC3261</a>].
The message-body can be a non-multipart message-body or a multipart
message-body as specified in [<a href="./rfc3261" title=""SIP: Session Initiation Protocol"">RFC3261</a>].
[<a id="ref-RFC5621">RFC5621</a>] defines generic handling of a multipart message-body in a
SIP message.
A multipart message-body contains zero, one, or several body parts
encoded using the format define in [<a href="./rfc2045" title=""Multipurpose Internet Mail Extensions (MIME) Part One: Format of Internet Message Bodies"">RFC2045</a>].
A body part in the multipart message-body is described using header
fields such as Content-Disposition, Content-Encoding, and Content-
Type, which provide information on the content of the body part as
specified in [<a href="./rfc5621" title=""Message Body Handling in the Session Initiation Protocol (SIP)"">RFC5621</a>]. A body part in the multipart message-body
can also contain a Content-ID header field with an ID value uniquely
identifying the body part as specified in [<a href="./rfc2045" title=""Multipurpose Internet Mail Extensions (MIME) Part One: Format of Internet Message Bodies"">RFC2045</a>].
<span class="h3"><a class="selflink" id="section-1.2" href="#section-1.2">1.2</a>. Referencing a Body Part</span>
A SIP header field can reference a body part using a Content-ID URL
as specified in [<a href="./rfc5621" title=""Message Body Handling in the Session Initiation Protocol (SIP)"">RFC5621</a>].
The Content-ID URL is specified in [<a href="./rfc2392" title=""Content-ID and Message-ID Uniform Resource Locators"">RFC2392</a>]. [<a href="./rfc2392" title=""Content-ID and Message-ID Uniform Resource Locators"">RFC2392</a>] specifies
how to identify the body part referenced by a Content-ID URL. The
Content-ID URL value is included in the Content-ID header field of
the body part.
Examples of SIP header fields referencing a body part using a
Content-ID URL are:
o [<a href="./rfc6442" title=""Location Conveyance for the Session Initiation Protocol"">RFC6442</a>] specifies how a Geolocation header field references a
body part using a Content-ID URL for providing location
information.
o [<a href="./rfc5368" title=""Referring to Multiple Resources in the Session Initiation Protocol (SIP)"">RFC5368</a>] specifies how a Refer-To header field references a body
part using a Content-ID URL to provide a list of targets.
<span class="grey">Holmberg & Sedlacek Standards Track [Page 3]</span></pre>
<hr class='noprint'/><!--NewPage--><pre class='newpage'><span id="page-4" ></span>
<span class="grey"><a href="./rfc8262">RFC 8262</a> Content-ID in SIP October 2017</span>
<span class="h3"><a class="selflink" id="section-1.3" href="#section-1.3">1.3</a>. Problem Statement</span>
How to uniquely identify a complete message-body of a SIP message
using a Content-ID header field and how to reference a complete
message-body using a Content-ID URL are not currently specified.
Note: In [<a href="./rfc5621" title=""Message Body Handling in the Session Initiation Protocol (SIP)"">RFC5621</a>], the Content-ID URL references a specific body
part only.
Some existing specifications, such as [<a href="./rfc5368" title=""Referring to Multiple Resources in the Session Initiation Protocol (SIP)"">RFC5368</a>], contain examples
that show usage of a SIP Content-ID header field referencing a
complete message-body, even though such usage has never been
specified. Many implementors have interpreted these examples to
indicate that such usage is allowed by the corresponding
specification, despite the absence of language allowing it. This
document updates the normative language in the affected documents to
explicitly allow such usage.
<span class="h3"><a class="selflink" id="section-1.4" href="#section-1.4">1.4</a>. Consequences</span>
The examples below show the consequences of the problem described
above.
<span class="h4"><a class="selflink" id="section-1.4.1" href="#section-1.4.1">1.4.1</a>. Example 1: SIP INVITE</span>
If a User Agent Client (UAC) sends an INVITE request that conveys
location by value (as specified in [<a href="./rfc6442" title=""Location Conveyance for the Session Initiation Protocol"">RFC6442</a>]) and decides not to
include a Session Description Protocol (SDP) offer, then the UAC
needs to include only one MIME entity in the INVITE request. This
MIME entity can be, for example, of the 'application/pidf+xml' MIME
type.
However, due to [<a href="./rfc6442" title=""Location Conveyance for the Session Initiation Protocol"">RFC6442</a>] requiring inclusion of a Geolocation header
field referencing the body part with the location information, the
UAC includes a multipart message-body with a single body part in the
INVITE request, and includes the location information of
'application/pidf+xml' MIME type and an associated Content-ID header
field in the body part.
<span class="grey">Holmberg & Sedlacek Standards Track [Page 4]</span></pre>
<hr class='noprint'/><!--NewPage--><pre class='newpage'><span id="page-5" ></span>
<span class="grey"><a href="./rfc8262">RFC 8262</a> Content-ID in SIP October 2017</span>
Example message (SIP INVITE):
INVITE sips:bob@biloxi.example.com SIP/2.0
Via: SIPS/2.0/TLS pc33.atlanta.example.com;branch=z9hG4bK74bf9
Max-Forwards: 70
To: Bob <sips:bob@biloxi.example.com>
From: Alice <sips:alice@atlanta.example.com>;tag=9fxced76sl
Call-ID: 3848276298220188511@atlanta.example.com
Geolocation: <cid:target123@atlanta.example.com>
Geolocation-Routing: no
Accept: application/sdp, application/pidf+xml
CSeq: 31862 INVITE
Contact: <sips:alice@atlanta.example.com>
Content-Type: multipart/mixed; boundary=boundary1
Content-Length: ...
--boundary1
Content-Type: application/pidf+xml
Content-ID: <target123@atlanta.example.com>
<?xml version="1.0" encoding="UTF-8"?>
<presence
xmlns="urn:ietf:params:xml:ns:pidf"
xmlns:gp="urn:ietf:params:xml:ns:pidf:geopriv10"
xmlns:gbp="urn:ietf:params:xml:ns:pidf:geopriv10:basicPolicy"
xmlns:cl="urn:ietf:params:xml:ns:pidf:geopriv10:civicAddr"
xmlns:gml="http://www.opengis.net/gml"
xmlns:dm="urn:ietf:params:xml:ns:pidf:data-model"
entity="pres:alice@atlanta.example.com"
>
<dm:device id="target123-1">
<gp:geopriv>
<gp:location-info>
<gml:location>
<gml:Point srsName="urn:ogc:def:crs:EPSG::4326">
<gml:pos>32.86726 -97.16054</gml:pos>
</gml:Point>
</gml:location>
</gp:location-info>
<gp:usage-rules>
<gbp:retransmission-allowed>no
</gbp:retransmission-allowed>
<gbp:retention-expiry>2010-11-14T20:00:00Z
</gbp:retention-expiry>
</gp:usage-rules>
<gp:method>802.11</gp:method>
</gp:geopriv>
<span class="grey">Holmberg & Sedlacek Standards Track [Page 5]</span></pre>
<hr class='noprint'/><!--NewPage--><pre class='newpage'><span id="page-6" ></span>
<span class="grey"><a href="./rfc8262">RFC 8262</a> Content-ID in SIP October 2017</span>
<dm:deviceID>mac:1234567890ab</dm:deviceID>
<dm:timestamp>2010-11-04T20:57:29Z</dm:timestamp>
</dm:device>
</presence>
--boundary1--
<span class="h4"><a class="selflink" id="section-1.4.2" href="#section-1.4.2">1.4.2</a>. Example 2: SIP REFER</span>
If a UAC sends a REFER request including a list of targets as
specified in [<a href="./rfc5368" title=""Referring to Multiple Resources in the Session Initiation Protocol (SIP)"">RFC5368</a>], then the UAC needs to include only one MIME
entity in the REFER request. This MIME entity is of the
'application/resource-lists+xml' MIME type.
However, due to [<a href="./rfc5368" title=""Referring to Multiple Resources in the Session Initiation Protocol (SIP)"">RFC5368</a>] requiring inclusion of a Refer-To header
field referencing the body part containing the list of targets, the
UAC includes a multipart message-body with a single body part in the
REFER request and includes the list of targets of 'application/
resource-lists+xml' MIME type and an associated Content-ID header
field in the body part.
Example message (SIP REFER):
REFER sip:conf-123@example.com;gruu;opaque=hha9s8d-999a SIP/2.0
Via: SIP/2.0/TCP client.chicago.example.com;branch=z9hG4bKhjhs8ass83
Max-Forwards: 70
To: "Conference 123" <sip:conf-123@example.com>
From: Carol <sip:carol@chicago.example.com>;tag=32331
Call-ID: d432fa84b4c76e66710
CSeq: 2 REFER
Contact: <sip:carol@client.chicago.example.com>
Refer-To: <cid:cn35t8jf02@example.com>
Refer-Sub: false
Require: multiple-refer, norefersub
Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, SUBSCRIBE, NOTIFY
Allow-Events: dialog
Accept: application/sdp, message/sipfrag
Content-Type: multipart/mixed; boundary=boundary1
Content-Length: ...
--boundary1
Content-Type: application/resource-lists+xml
Content-Disposition: recipient-list
Content-ID: <cn35t8jf02@example.com>
<span class="grey">Holmberg & Sedlacek Standards Track [Page 6]</span></pre>
<hr class='noprint'/><!--NewPage--><pre class='newpage'><span id="page-7" ></span>
<span class="grey"><a href="./rfc8262">RFC 8262</a> Content-ID in SIP October 2017</span>
<?xml version="1.0" encoding="UTF-8"?>
<resource-lists
xmlns="urn:ietf:params:xml:ns:resource-lists"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
>
<list>
<entry uri="sip:bill@example.com?method=BYE"/>
<entry uri="sip:joe@example.org?method=BYE"/>
<entry uri="sip:ted@example.net?method=BYE"/>
</list>
</resource-lists>
--boundary1--
<span class="h3"><a class="selflink" id="section-1.5" href="#section-1.5">1.5</a>. Solution</span>
In order to solve the problems described above, this document:
o Specifies and registers the Content-ID header field as a SIP
header field.
o Specifies that, when used as a SIP header field, the Content-ID
header field identifies the complete message-body and the metadata
provided by some additional SIP header fields of the SIP message.
o Updates [<a href="./rfc5621" title=""Message Body Handling in the Session Initiation Protocol (SIP)"">RFC5621</a>] to enable a Content-ID URL to reference a
complete message-body and the metadata provided by some additional
SIP header fields.
o Updates [<a href="./rfc5368" title=""Referring to Multiple Resources in the Session Initiation Protocol (SIP)"">RFC5368</a>] and [<a href="./rfc6442" title=""Location Conveyance for the Session Initiation Protocol"">RFC6442</a>] by adding text that explicitly
states that a SIP Content-ID header field can be used.
<span class="h3"><a class="selflink" id="section-1.6" href="#section-1.6">1.6</a>. Backward Compatibility</span>
If an existing specification only defines the usage of a multipart
message-body to carry a single body part to be referenced by a
Content-ID URL, implementations MUST NOT carry the MIME entity in a
non-multipart message-body unless the specification is updated to
explicitly allow it.
<span class="h2"><a class="selflink" id="section-2" href="#section-2">2</a>. Conventions</span>
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 <a href="https://www.rfc-editor.org/bcp/bcp14">BCP</a>
<a href="https://www.rfc-editor.org/bcp/bcp14">14</a> [<a href="./rfc2119" title=""Key words for use in RFCs to Indicate Requirement Levels"">RFC2119</a>] [<a href="./rfc8174" title=""Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words"">RFC8174</a>] when, and only when, they appear in all
capitals, as shown here.
<span class="grey">Holmberg & Sedlacek Standards Track [Page 7]</span></pre>
<hr class='noprint'/><!--NewPage--><pre class='newpage'><span id="page-8" ></span>
<span class="grey"><a href="./rfc8262">RFC 8262</a> Content-ID in SIP October 2017</span>
<span class="h2"><a class="selflink" id="section-3" href="#section-3">3</a>. Content-ID Header Field</span>
<span class="h3"><a class="selflink" id="section-3.1" href="#section-3.1">3.1</a>. Introduction</span>
This section defines the usage of the Content-ID header field for
SIP.
<span class="h3"><a class="selflink" id="section-3.2" href="#section-3.2">3.2</a>. Syntax</span>
The ABNF [<a href="./rfc5234" title=""Augmented BNF for Syntax Specifications: ABNF"">RFC5234</a>] for the Content-ID header field is:
Content-ID = "Content-ID" HCOLON msg-id
msg-id = "<" id-left "@" id-right ">"
Note: id-left and id-right are specified in [<a href="./rfc5322" title=""Internet Message Format"">RFC5322</a>]. HCOLON is
defined in [<a href="./rfc3261" title=""SIP: Session Initiation Protocol"">RFC3261</a>].
Note: When used in a SIP header field, the msg-id syntax has been
simplified, compared to the syntax in [<a href="./rfc5322" title=""Internet Message Format"">RFC5322</a>], to disallow the use
of comments and to adopt to the SIP usage of leading white space.
The value of the Content-ID header field value must be unique in the
context of a given SIP message, including any embedded MIME
Content-ID header field values. Note that the SIP Content-ID header
field value is not expected to be unique among all SIP messages; it
has no meaning outside of the message in which it is included.
<span class="h3"><a class="selflink" id="section-3.3" href="#section-3.3">3.3</a>. Semantics</span>
The Content-ID header field included in the header fields of a SIP
message identifies the message-body of the SIP message and the
metadata provided by:
o A MIME-Version header field, if included in the header fields of
the SIP message.
o Any 'Content-' prefixed header fields (including the Content-ID
header field itself) included in the header fields of the SIP
message.
The Content-ID header field can be included in any SIP message that
is allowed to contain a message-body.
Note: The message-body identified by the Content-ID header field can
be a non-multipart message-body or a multipart message-body.
<span class="grey">Holmberg & Sedlacek Standards Track [Page 8]</span></pre>
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<span class="grey"><a href="./rfc8262">RFC 8262</a> Content-ID in SIP October 2017</span>
<span class="h3"><a class="selflink" id="section-3.4" href="#section-3.4">3.4</a>. Procedures</span>
<span class="h4"><a class="selflink" id="section-3.4.1" href="#section-3.4.1">3.4.1</a>. User Agent (UA) Procedures</span>
A UA MAY include a Content-ID header field in any SIP message that is
allowed to contain a message-body.
A UA MUST NOT include a Content-ID header field in any SIP message
that is not allowed to contain a message-body.
A UA MUST set the value of the Content-ID header field to a value
that is unique in the context of the SIP message.
<span class="h4"><a class="selflink" id="section-3.4.2" href="#section-3.4.2">3.4.2</a>. Proxy Procedures</span>
A proxy MUST NOT add a Content-ID header field in a SIP message.
A proxy MUST NOT modify a Content-ID header field included in a SIP
message.
A proxy MUST NOT delete a Content-ID header field from a SIP message.
<span class="h4"><a class="selflink" id="section-3.4.3" href="#section-3.4.3">3.4.3</a>. Example: Referencing the Message-Body of a SIP Message</span>
The figure shows an example from [<a href="./rfc5368" title=""Referring to Multiple Resources in the Session Initiation Protocol (SIP)"">RFC5368</a>], where the SIP Content-ID
header field is used to reference the message-body (non-multipart) of
a SIP message.
REFER sip:conf-123@example.com;gruu;opaque=hha9s8d-999a SIP/2.0
Via: SIP/2.0/TCP client.chicago.example.com
;branch=z9hG4bKhjhs8ass83
Max-Forwards: 70
To: "Conference 123" <sip:conf-123@example.com>
From: Carol <sip:carol@chicago.example.com>;tag=32331
Call-ID: d432fa84b4c76e66710
CSeq: 2 REFER
Contact: <sip:carol@client.chicago.example.com>
Refer-To: <cid:cn35t8jf02@example.com>
Refer-Sub: false
Require: multiple-refer, norefersub
Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, SUBSCRIBE, NOTIFY
Allow-Events: dialog
Accept: application/sdp, message/sipfrag
Content-Type: application/resource-lists+xml
Content-Disposition: recipient-list
Content-Length: 362
Content-ID: <cn35t8jf02@example.com>
<span class="grey">Holmberg & Sedlacek Standards Track [Page 9]</span></pre>
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<span class="grey"><a href="./rfc8262">RFC 8262</a> Content-ID in SIP October 2017</span>
<?xml version="1.0" encoding="UTF-8"?>
<resource-lists xmlns="urn:ietf:params:xml:ns:resource-lists"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
<list>
<entry uri="sip:bill@example.com?method=BYE" />
<entry uri="sip:joe@example.org?method=BYE" />
<entry uri="sip:ted@example.net?method=BYE" />
</list>
</resource-lists>
<span class="h2"><a class="selflink" id="section-4" href="#section-4">4</a>. Update to <a href="./rfc5368">RFC 5368</a></span>
This section updates the second paragraph in <a href="./rfc5368#section-7">Section 7 of [RFC5368]</a>
by allowing usage of either a MIME Content-ID header field or a SIP
Content-ID header field to label the body part or the message-body
carrying the URI list.
OLD TEXT:
The Refer-To header field of a REFER request with multiple REFER-
Targets MUST contain a pointer (i.e., a Content-ID Uniform
Resource Locator (URL) as per <a href="./rfc2392">RFC 2392</a> [<a href="./rfc2392" title=""Content-ID and Message-ID Uniform Resource Locators"">RFC2392</a>]) that points to
the body part that carries the URI list. The REFER-Issuer SHOULD
NOT include any particular URI more than once in the URI list.
NEW TEXT:
The Refer-To header field of a REFER request with multiple REFER-
Targets MUST contain a pointer (i.e., a Content-ID Uniform
Resource Locator (URL) as per <a href="./rfc2392">RFC 2392</a> [<a href="./rfc2392" title=""Content-ID and Message-ID Uniform Resource Locators"">RFC2392</a>]) that points to
the body part or message-body that carries the URI list. The
REFER-Issuer SHOULD NOT include any particular URI more than once
in the URI list. The REFER request can use either a MIME Content-
ID header field [<a href="./rfc4483" title=""A Mechanism for Content Indirection in Session Initiation Protocol (SIP) Messages"">RFC4483</a>] or a SIP Content-ID header field
[<a href="./rfc8262">RFC8262</a>] to label the body part or the message-body.
<span class="grey">Holmberg & Sedlacek Standards Track [Page 10]</span></pre>
<hr class='noprint'/><!--NewPage--><pre class='newpage'><span id="page-11" ></span>
<span class="grey"><a href="./rfc8262">RFC 8262</a> Content-ID in SIP October 2017</span>
<span class="h2"><a class="selflink" id="section-5" href="#section-5">5</a>. Update to <a href="./rfc5621">RFC 5621</a></span>
This section updates <a href="./rfc5621#section-9.1">Section 9.1 of [RFC5621]</a> by allowing a Content-
ID URL to reference a message-body and the related metadata
(<a href="#section-3.3">Section 3.3</a>) in addition to allowing a reference to a body part.
OLD TEXT:
Content-ID URLs allow creating references to body parts. A given
Content-ID URL [<a href="./rfc2392" title=""Content-ID and Message-ID Uniform Resource Locators"">RFC2392</a>], which can appear in a header field or
within a body part (e.g., in an SDP attribute), points to a
particular body part.
NEW TEXT:
Content-ID URLs allow the creation of references to body parts or
message-bodies (and the header fields describing the message-
bodies). A given Content-ID URL [<a href="./rfc2392" title=""Content-ID and Message-ID Uniform Resource Locators"">RFC2392</a>], which can appear in a
header field or within a body part (e.g., in an SDP attribute),
points to a particular body part or the message-body (and the
header fields describing the message-body).
<span class="h2"><a class="selflink" id="section-6" href="#section-6">6</a>. Update to <a href="./rfc6442">RFC 6442</a></span>
This section updates the second paragraph in <a href="./rfc6442#section-3.1">Section 3.1 of [RFC6442]</a>
by allowing usage of either a MIME Content-ID header field or a SIP
Content-ID header field to label the body part or the message-body
carrying the location data.
OLD TEXT:
In Figure 1, Alice is both the Target and the LS that is conveying
her location directly to Bob, who acts as an LR. This conveyance
is point-to-point: it does not pass through any SIP-layer
intermediary. A Location Object appears by-value in the initial
SIP request as a MIME body, and Bob responds to that SIP request
as appropriate. There is a 'Bad Location Information' response
code introduced within this document to specifically inform Alice
if she conveys bad location information to Bob (e.g., Bob "cannot
parse the location provided", or "there is not enough location
information to determine where Alice is").
<span class="grey">Holmberg & Sedlacek Standards Track [Page 11]</span></pre>
<hr class='noprint'/><!--NewPage--><pre class='newpage'><span id="page-12" ></span>
<span class="grey"><a href="./rfc8262">RFC 8262</a> Content-ID in SIP October 2017</span>
NEW TEXT:
In Figure 1, Alice is both the Target and the LS that is conveying
her location directly to Bob, who acts as an LR. This conveyance
is point-to-point: it does not pass through any SIP-layer
intermediary. A Location Object appears by-value in the initial
SIP request as a MIME body, and Bob responds to that SIP request
as appropriate. Either a MIME Content-ID header field [<a href="./rfc4483" title=""A Mechanism for Content Indirection in Session Initiation Protocol (SIP) Messages"">RFC4483</a>]
or the SIP Content-ID header field [<a href="./rfc8262">RFC8262</a>] MUST be used to label
the location information. There is a 'Bad Location Information'
response code introduced within this document to specifically
inform Alice if she conveys bad location information to Bob (e.g.,
Bob "cannot parse the location provided", or "there is not enough
location information to determine where Alice is").
<span class="h2"><a class="selflink" id="section-7" href="#section-7">7</a>. Security Considerations</span>
The Content-ID header field value MUST NOT reveal sensitive user
information.
If the message-body associated with the Content-ID header field is an
encrypted body, it MUST NOT be possible to derive a key that can be
used to decrypt the body from the Content-ID header field value.
<span class="h2"><a class="selflink" id="section-8" href="#section-8">8</a>. IANA Considerations</span>
This specification registers a new SIP header field according to the
procedures defined in [<a href="./rfc3261" title=""SIP: Session Initiation Protocol"">RFC3261</a>].
<span class="h3"><a class="selflink" id="section-8.1" href="#section-8.1">8.1</a>. Header Field</span>
The header field described in <a href="#section-3">Section 3</a> has been registered in the
"Header Fields" sub-registry of the "Session Initiation Protocol
(SIP) Parameters" registry by adding a row with these values:
Header Name: Content-ID
compact:
Reference: <a href="./rfc8262">RFC 8262</a>
<span class="grey">Holmberg & Sedlacek Standards Track [Page 12]</span></pre>
<hr class='noprint'/><!--NewPage--><pre class='newpage'><span id="page-13" ></span>
<span class="grey"><a href="./rfc8262">RFC 8262</a> Content-ID in SIP October 2017</span>
<span class="h2"><a class="selflink" id="section-9" href="#section-9">9</a>. References</span>
<span class="h3"><a class="selflink" id="section-9.1" href="#section-9.1">9.1</a>. Normative References</span>
[<a id="ref-RFC2045">RFC2045</a>] Freed, N. and N. Borenstein, "Multipurpose Internet Mail
Extensions (MIME) Part One: Format of Internet Message
Bodies", <a href="./rfc2045">RFC 2045</a>, DOI 10.17487/RFC2045, November 1996,
<<a href="https://www.rfc-editor.org/info/rfc2045">https://www.rfc-editor.org/info/rfc2045</a>>.
[<a id="ref-RFC2119">RFC2119</a>] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", <a href="https://www.rfc-editor.org/bcp/bcp14">BCP 14</a>, <a href="./rfc2119">RFC 2119</a>,
DOI 10.17487/RFC2119, March 1997,
<<a href="https://www.rfc-editor.org/info/rfc2119">https://www.rfc-editor.org/info/rfc2119</a>>.
[<a id="ref-RFC2392">RFC2392</a>] Levinson, E., "Content-ID and Message-ID Uniform Resource
Locators", <a href="./rfc2392">RFC 2392</a>, DOI 10.17487/RFC2392, August 1998,
<<a href="https://www.rfc-editor.org/info/rfc2392">https://www.rfc-editor.org/info/rfc2392</a>>.
[<a id="ref-RFC3261">RFC3261</a>] Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston,
A., Peterson, J., Sparks, R., Handley, M., and E.
Schooler, "SIP: Session Initiation Protocol", <a href="./rfc3261">RFC 3261</a>,
DOI 10.17487/RFC3261, June 2002,
<<a href="https://www.rfc-editor.org/info/rfc3261">https://www.rfc-editor.org/info/rfc3261</a>>.
[<a id="ref-RFC4483">RFC4483</a>] Burger, E., Ed., "A Mechanism for Content Indirection in
Session Initiation Protocol (SIP) Messages", <a href="./rfc4483">RFC 4483</a>,
DOI 10.17487/RFC4483, May 2006,
<<a href="https://www.rfc-editor.org/info/rfc4483">https://www.rfc-editor.org/info/rfc4483</a>>.
[<a id="ref-RFC5234">RFC5234</a>] Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax
Specifications: ABNF", STD 68, <a href="./rfc5234">RFC 5234</a>,
DOI 10.17487/RFC5234, January 2008,
<<a href="https://www.rfc-editor.org/info/rfc5234">https://www.rfc-editor.org/info/rfc5234</a>>.
[<a id="ref-RFC5322">RFC5322</a>] Resnick, P., Ed., "Internet Message Format", <a href="./rfc5322">RFC 5322</a>,
DOI 10.17487/RFC5322, October 2008,
<<a href="https://www.rfc-editor.org/info/rfc5322">https://www.rfc-editor.org/info/rfc5322</a>>.
[<a id="ref-RFC5621">RFC5621</a>] Camarillo, G., "Message Body Handling in the Session
Initiation Protocol (SIP)", <a href="./rfc5621">RFC 5621</a>,
DOI 10.17487/RFC5621, September 2009,
<<a href="https://www.rfc-editor.org/info/rfc5621">https://www.rfc-editor.org/info/rfc5621</a>>.
[<a id="ref-RFC8174">RFC8174</a>] Leiba, B., "Ambiguity of Uppercase vs Lowercase in <a href="./rfc2119">RFC</a>
<a href="./rfc2119">2119</a> Key Words", <a href="https://www.rfc-editor.org/bcp/bcp14">BCP 14</a>, <a href="./rfc8174">RFC 8174</a>, DOI 10.17487/RFC8174,
May 2017, <<a href="https://www.rfc-editor.org/info/rfc8174">https://www.rfc-editor.org/info/rfc8174</a>>.
<span class="grey">Holmberg & Sedlacek Standards Track [Page 13]</span></pre>
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<span class="grey"><a href="./rfc8262">RFC 8262</a> Content-ID in SIP October 2017</span>
<span class="h3"><a class="selflink" id="section-9.2" href="#section-9.2">9.2</a>. Informative References</span>
[<a id="ref-RFC5368">RFC5368</a>] Camarillo, G., Niemi, A., Isomaki, M., Garcia-Martin, M.,
and H. Khartabil, "Referring to Multiple Resources in the
Session Initiation Protocol (SIP)", <a href="./rfc5368">RFC 5368</a>,
DOI 10.17487/RFC5368, October 2008,
<<a href="https://www.rfc-editor.org/info/rfc5368">https://www.rfc-editor.org/info/rfc5368</a>>.
[<a id="ref-RFC6442">RFC6442</a>] Polk, J., Rosen, B., and J. Peterson, "Location Conveyance
for the Session Initiation Protocol", <a href="./rfc6442">RFC 6442</a>,
DOI 10.17487/RFC6442, December 2011,
<<a href="https://www.rfc-editor.org/info/rfc6442">https://www.rfc-editor.org/info/rfc6442</a>>.
Authors' Addresses
Christer Holmberg
Ericsson
Hirsalantie 11
Jorvas 02420
Finland
Email: christer.holmberg@ericsson.com
Ivo Sedlacek
Ericsson
Sokolovska 79
Praha 18600
Czech Republic
Email: ivo.sedlacek@ericsson.com
Holmberg & Sedlacek Standards Track [Page 14]
</pre>
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