SIPCORE Working Group C. Holmberg
Internet-Draft I. Sedlacek
Updates: 5621 (if approved) Ericsson
Intended status: Standards Track May 8, 2017
Expires: November 9, 2017
Content-ID header field in Session Initiation Protocol (SIP)
draft-ietf-sipcore-content-id-04
Abstract
This document specifies the Content-ID header field for usage in the
Session Initiation Protocol (SIP). The document also updates RFC
5621, to enable a Content-ID URL to reference a complete message-body
and metadata provided by some additional SIP header fields.
Status of This Memo
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Identifying a body part . . . . . . . . . . . . . . . . . 2
1.2. Referencing a body part . . . . . . . . . . . . . . . . . 3
1.3. Problem statement . . . . . . . . . . . . . . . . . . . . 3
1.4. Consequences . . . . . . . . . . . . . . . . . . . . . . 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 . . . . . . . . . . . . . . . . . . . 4
3.1. Introduction . . . . . . . . . . . . . . . . . . . . . . 4
3.2. Syntax . . . . . . . . . . . . . . . . . . . . . . . . . 5
3.3. Semantics . . . . . . . . . . . . . . . . . . . . . . . . 5
3.4. Procedures . . . . . . . . . . . . . . . . . . . . . . . 5
3.4.1. UA procedures . . . . . . . . . . . . . . . . . . . . 5
3.4.2. Proxy procedures . . . . . . . . . . . . . . . . . . 6
4. Update to RFC 5621 . . . . . . . . . . . . . . . . . . . . . 6
5. Security considerations . . . . . . . . . . . . . . . . . . . 6
6. IANA considerations . . . . . . . . . . . . . . . . . . . . . 6
6.1. Header field . . . . . . . . . . . . . . . . . . . . . . 7
7. Change log . . . . . . . . . . . . . . . . . . . . . . . . . 7
8. Normative references . . . . . . . . . . . . . . . . . . . . 7
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 8
1. Introduction
1.1. Identifying a body part
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].
The message-body can be a non-multipart message-body or a multipart
message-body as specified in [RFC3261].
[RFC5621] 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 [RFC2045] format.
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 [RFC5621]. A body part in the multipart message-body
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can also contain a Content-ID header field with an ID value uniquely
identifying the body part, as specified in [RFC2045].
1.2. Referencing a body part
A SIP header field can reference a body part using a Content-ID URL,
as specified in [RFC5621].
The Content-ID URL is specified in [RFC2392]. [RFC2392] 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 [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
It is currently not specified 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.
1.4. Consequences
The examples below shows the consequences of the problem described
above.
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 only one
MIME entity in the INVITE request. This content can be e.g. of the
application/pidf+xml MIME type.
However, due to [RFC6442] requiring inclusion of a Geolocation header
field referencing the body part with the location information, the
UAC includes a multipart message-body with 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.
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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 only one MIME
entity in the REFER request. This content 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 includes a multipart message-body with 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.
1.5. Solution
In order to solve the problems described above, this document:
o Specifies and registers the Content-ID header field as a SIP
header field; and
o Specifies that, when used as a SIP header field, the Content-ID
header field identifies the complete message-body, and metadata
provided by some additional SIP header fields, of the SIP message;
and
o Updates [RFC5621], to enable a Content-ID URL to reference a
complete message-body and metadata provided by some additional SIP
header fields.
NOTE: In [RFC5621], the Content-ID URL references a specific body
part only.
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].
3. Content-ID header field
3.1. Introduction
This section defines the usage of the Content-ID header field for
SIP.
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3.2. Syntax
The ABNF [RFC5234] 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 [RFC5322]. HCOLON is
defined in [RFC3261].
NOTE: When used in a SIP header field, the msg-id syntax has been
simplified compared to the syntax in [RFC5322].
3.3. Semantics
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; and
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 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 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.
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. Update to RFC 5621
This section updates section 9.1 of [RFC5621], by allowing a Content-
ID URL to reference a message-body and the related metadata
(Section 3.3), 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 [RFC2392], 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 creating references to body parts or
message-bodies (and the header fields describing the
message-bodies). A given Content-ID URL [RFC2392], 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).
5. 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 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.
6. IANA considerations
This specification registers a new SIP header field according to the
procedures in [RFC3261].
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6.1. Header field
The header field described in Section 3 has been registered in the
"Header Fields" sub-registry of the "Session Initiation Protocol
(SIP) Parameters" registry by adding a row with these values:
[RFC EDITOR NOTE: Please replace XXXX with the RFC number of this
document when publishing]
Header Name: Content-ID
compact:
Reference: RFCXXXX
7. Change log
[RFC EDITOR NOTE: Please remove this section when publishing]
Changes from draft-ietf-sipcore-content-id-03
o Changes based on doc shepard review:
o - Reference to RFC 5234 added.
o - Editorial changes.
Changes from draft-ietf-sipcore-content-id-02
o Editorial changes based on comments from Paul Kyzivat.
Changes from draft-ietf-sipcore-content-id-01
o Update to RFC 5621 added.
o Editorial changes.
8. 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>.
[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>.
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[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>.
[RFC5234] Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax
Specifications: ABNF", STD 68, RFC 5234,
DOI 10.17487/RFC5234, January 2008,
<http://www.rfc-editor.org/info/rfc5234>.
[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
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