SIPCORE Working Group C. Holmberg
Internet-Draft I. Sedlacek
Intended status: Standards Track Ericsson
Expires: August 3, 2017 January 30, 2017
Content ID header field in Session Initiation Protocol (SIP)
draft-ietf-sipcore-content-id-00
Abstract
This document specifies the Content-ID header field for usage in the
Session Initiation Protocol (SIP).
Status of This Memo
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Setting up ID value uniquely identifying the body . . . . 2
1.2. Referencing the ID value uniquely identifying the body . 3
1.3. Problem statement . . . . . . . . . . . . . . . . . . . . 3
1.4. Examples of the problem . . . . . . . . . . . . . . . . . 3
1.4.1. Example 1 . . . . . . . . . . . . . . . . . . . . . . 3
1.4.2. Example 2 . . . . . . . . . . . . . . . . . . . . . . 4
1.5. Solution . . . . . . . . . . . . . . . . . . . . . . . . 4
2. Conventions . . . . . . . . . . . . . . . . . . . . . . . . . 4
3. Content-ID header field . . . . . . . . . . . . . . . . . . . 5
3.1. Introduction . . . . . . . . . . . . . . . . . . . . . . 5
3.2. Syntax . . . . . . . . . . . . . . . . . . . . . . . . . 5
3.3. Semantic . . . . . . . . . . . . . . . . . . . . . . . . 5
3.4. Procedures . . . . . . . . . . . . . . . . . . . . . . . 5
3.4.1. UA procedures . . . . . . . . . . . . . . . . . . . . 5
3.4.2. Proxy procedures . . . . . . . . . . . . . . . . . . 6
4. Security Considerations . . . . . . . . . . . . . . . . . . . 6
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6
5.1. Header Field . . . . . . . . . . . . . . . . . . . . . . 6
6. Change Log . . . . . . . . . . . . . . . . . . . . . . . . . 6
7. Normative References . . . . . . . . . . . . . . . . . . . . 6
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 7
1. Introduction
1.1. Setting up ID value uniquely identifying the body
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 [RFC3261].
A message-body of the SIP message can contain one body only or can
contain several bodies, as specified in [RFC3261].
When the message-body of the SIP message contains several bodies,
each body is included in a body part encoded using [RFC2045] format
in the message-body of the SIP message, as specified in [RFC5621]. A
body part encoded using [RFC2045] format can contain a Content-ID
header field with an ID value uniquely identifying the body part, as
specified in [RFC2045].
However, when the message-body of the SIP message contains one body
only, there are no body parts and there is also no defined method how
to convey an ID value uniquely identifying the body part. Also, the
Content-ID header field is not a defined SIP header field and thus
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the Content-ID header field cannot be included in the header fields
of a SIP message.
1.2. Referencing the ID value uniquely identifying the body
A SIP header field can contain a reference to a body part using a
Content-ID URL, as specified in [RFC5621].
The Content-ID URL is specified in [RFC2392]. [RFC2392] also
specifies how to discover the body part referenced by a Content-ID
URL.
Examples of a SIP header field referencing a body part using a
Content-ID URL are:
o [RFC6442] specifies how a Geolocation header field references a
body part using a Content-ID URL, for providing location.
o [RFC5368] specifies how a Refer-To header field references a body
part using a Content-ID URL, to provide a list of targets.
1.3. Problem statement
Since the Content-ID header field is not a defined SIP header field:
o When solely one body needs to be transported in a SIP message, if
a UAC does not need to include in the SIP message a SIP header
field referencing the body part, the UAC sets the message-body to
the body.
o However, when solely one body needs to be transported in a SIP
message, if a UAC needs to include in the SIP message a SIP header
field referencing the body part, then the UAC needs to include the
body in a body part encoded using the [RFC2045] format. I.e., the
UAC sets the message-body using [RFC2045] format and includes one
body part with the body and associated Content-ID header field.
1.4. Examples of the problem
1.4.1. Example 1
If a UAC sends an INVITE request conveying location as specified in
[RFC6442], if the UAC decides not to include an SDP offer, and if the
location is conveyed by value, then the UAC needs to include one body
only in the INVITE request.
This body contains the location information and can be e.g. of the
application/pidf+xml MIME type.
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However, due to [RFC6442] requiring inclusion of a Geolocation header
field referencing the body part with the body containing the location
information, the UAC needs to include a message-body of multipart/
mixed MIME type in the INVITE request, and the UAC needs to include a
body part with the application/pidf+xml body and associated Content-
ID header field in the multipart/mixed body.
1.4.2. Example 2
If a UAC sends an REFER request including a list of targets as
specified in [RFC5368], then the UAC needs to include one body only
in the REFER request.
This body contains the list of targets and is of the application/
resource-lists+xml MIME type.
However, due to [RFC5368] requiring inclusion of a Refer-To header
field referencing the body part containing the list of targets, the
UAC needs to include a message-body of the multipart/mixed MIME type
in the REFER request and the UE needs to include a body part with the
application/resource-lists+xml body and associated Content-ID header
field in the multipart/mixed body.
1.5. Solution
To avoid the unnecessary usage of the [RFC2045] format when only one
body needs to be included in a SIP message, this document specifies a
Content-ID header field as a SIP header field.
The Content-ID header field included in header fields of a SIP
message identifies a body part consisting of the message-body of the
SIP message and:
o a Content-Disposition header field;
o a Content-Encoding header field;
o a Content-Language header field;
o a Content-Length header field;
o a Content-Type header field; and
o a Content-ID header field;
included in the header fields of the SIP message.
2. Conventions
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119].
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3. Content-ID header field
3.1. Introduction
This section defines the usage of the Content-ID header field for
SIP.
3.2. Syntax
The ABNF for the Content-ID header fields is:
Content-ID = "Content-ID" HCOLON msg-id
NOTE: msg-id is specified in [RFC5322].
3.3. Semantic
A Content-ID header field included in header fields of a SIP message
indicates a globally unique identification of a body part consisting
of the message-body of the SIP message and:
o a Content-Disposition header field;
o a Content-Encoding header field;
o a Content-Language header field;
o a Content-Length header field;
o a Content-Type header field; and
o a Content-ID header field;
included in header fields of the SIP message.
The Content-ID header field can be included in any SIP message which
is allowed to contain a message-body.
3.4. Procedures
3.4.1. UA procedures
A UA MAY include a Content-ID header field in any SIP message which
is allowed to contain a message-body.
A UA MUST NOT include a Content-ID header field in any SIP message
which is not allowed to contain a message-body.
The UA MUST set the value of the Content-ID header field to a
globally unique value.
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3.4.2. Proxy procedures
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.
4. Security Considerations
The Content-ID header field value MUST NOT reveal sensitive user
information.
If the message-body associated with the Content-ID header field
contains encrypted content, it MUST NOT be possible to derive a key
that can be used to decrypt the message-body content from the
Content-ID header field value.
5. IANA Considerations
This specification registers a new SIP header field according to the
procedures in [RFC3261].
5.1. Header Field
[RFC EDITOR NOTE: Please replace XXXX with the RFC number of this
document when publishing]
RFC Number: RFC XXXX
Header Field Name: Content-ID
Compact Form: none
6. Change Log
[RFC EDITOR NOTE: Please remove this section when publishing]
TBD
7. Normative References
[RFC2045] Freed, N. and N. Borenstein, "Multipurpose Internet Mail
Extensions (MIME) Part One: Format of Internet Message
Bodies", RFC 2045, DOI 10.17487/RFC2045, November 1996,
<http://www.rfc-editor.org/info/rfc2045>.
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[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<http://www.rfc-editor.org/info/rfc2119>.
[RFC2392] Levinson, E., "Content-ID and Message-ID Uniform Resource
Locators", RFC 2392, DOI 10.17487/RFC2392, August 1998,
<http://www.rfc-editor.org/info/rfc2392>.
[RFC5322] Resnick, P., Ed., "Internet Message Format", RFC 5322,
DOI 10.17487/RFC5322, October 2008,
<http://www.rfc-editor.org/info/rfc5322>.
[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,
<http://www.rfc-editor.org/info/rfc3261>.
[RFC5368] Camarillo, G., Niemi, A., Isomaki, M., Garcia-Martin, M.,
and H. Khartabil, "Referring to Multiple Resources in the
Session Initiation Protocol (SIP)", RFC 5368,
DOI 10.17487/RFC5368, October 2008,
<http://www.rfc-editor.org/info/rfc5368>.
[RFC5621] Camarillo, G., "Message Body Handling in the Session
Initiation Protocol (SIP)", RFC 5621,
DOI 10.17487/RFC5621, September 2009,
<http://www.rfc-editor.org/info/rfc5621>.
[RFC6442] Polk, J., Rosen, B., and J. Peterson, "Location Conveyance
for the Session Initiation Protocol", RFC 6442,
DOI 10.17487/RFC6442, December 2011,
<http://www.rfc-editor.org/info/rfc6442>.
Authors' Addresses
Christer Holmberg
Ericsson
Hirsalantie 11
Jorvas 02420
Finland
Email: christer.holmberg@ericsson.com
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Ivo Sedlacek
Ericsson
Sokolovska 79
Praha 18600
Czech Republic
Email: ivo.sedlacek@ericsson.com
Holmberg & Sedlacek Expires August 3, 2017 [Page 8]
