SIPCORE Working Group                                        C. Holmberg
Internet-Draft                                               I. Sedlacek
Updates: 5621 (if approved)                                     Ericsson
Intended status: Standards Track                                Ericsson
Expires: September 9,                          April 25, 2017                                 March 8,
Expires: October 27, 2017

      Content ID

      Content-ID header field in Session Initiation Protocol (SIP)
                    draft-ietf-sipcore-content-id-01
                    draft-ietf-sipcore-content-id-02

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 refer a complete message-body and
   metadata provided by some additional SIP header fields.

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
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   This Internet-Draft will expire on September 9, October 27, 2017.

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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  Setting up ID value uniquely identifying  Identifying a body part . . . . . . . . . . . . . . . . .   2
     1.2.  Referencing the ID value uniquely identifying  Referring a body part . . . . . . . . . . . . . . . . . .   3
     1.3.  Problem statement . . . . . . . . . . . . . . . . . . . .   3
     1.4.  Examples of the problem  Consequencies . . . . . . . . . . . . . . . . . . . . . .   3
       1.4.1.  Example 1 . . . . . . . . . . . . . . . . . . . . . .   3
       1.4.2.  Example 2 . . . . . . . . . . . . . . . . . . . . . .   4
     1.5.  Solution  . . . . . . . . . . . . . . . . . . . . . . . .   4
   2.  Conventions . . . . . . . . . . . . . . . . . . . . . . . . .   5   4
   3.  Content-ID header field . . . . . . . . . . . . . . . . . . .   5   4
     3.1.  Introduction  . . . . . . . . . . . . . . . . . . . . . .   5   4
     3.2.  Syntax  . . . . . . . . . . . . . . . . . . . . . . . . .   5
     3.3.  Semantic  Semantics . . . . . . . . . . . . . . . . . . . . . . . .   5
     3.4.  Procedures  . . . . . . . . . . . . . . . . . . . . . . .   6   5
       3.4.1.  UA procedures . . . . . . . . . . . . . . . . . . . .   6   5
       3.4.2.  Proxy procedures  . . . . . . . . . . . . . . . . . .   6
   4.  Security Considerations  Update to RFC 5621  . . . . . . . . . . . . . . . . . . . . .   6
   5.  Security considerations . . . . . . . . . . . . . . . . . . .   6
   6.  IANA Considerations considerations . . . . . . . . . . . . . . . . . . . . .   6
     5.1.   7
     6.1.  Header Field field  . . . . . . . . . . . . . . . . . . . . . .   6
   6.   7
   7.  Change Log log  . . . . . . . . . . . . . . . . . . . . . . . . .   7
   7.
   8.  Normative References references  . . . . . . . . . . . . . . . . . . . .   7
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   8

1.  Introduction

1.1.  Setting up ID value uniquely identifying  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].

   A

   The message-body can be a non-multipart message-body or a multipart
   message-body as specified in [RFC3261].

   [RFC5621] defines generic handling of the a multipart message-body in a
   SIP message can contain message.

   A multipart message-body contains zero, one body only or can
   contain 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 [RFC3261] and [RFC5621].  A body part encoded using [RFC2045] 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 [RFC2045].

   However, when the message-body of the SIP message contains one body
   only, there is no body part specified.  Thus, there is also no
   defined method how to convey an ID value uniquely identifying the
   body part.

1.2.  Referencing the ID value uniquely identifying  Referring a body part

   A SIP header field can contain a reference to refer 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 identify the body part referenced referred by a Content-ID URL.  The
   Content-ID URL value is included in the Content-ID header field of
   the body part.

   Examples of a SIP header field referencing fields referring a body part using a
   Content-ID Content-
   ID URL are:

   o  [RFC6442] specifies how a Geolocation header field references refers a body
      part using a Content-ID URL, for providing location.
   o  [RFC5368] specifies how a Refer-To header field references refers a body part
      using a Content-ID URL, to provide a list of targets.

1.3.  Problem statement

   Since the Content-ID header field

   It is currently not a defined SIP header field:

   o  If solely one body needs specified how to be transported in uniquely identify a complete
   message-body of a SIP message and
      the UAC does not need to include in the SIP message using a SIP Content-ID header
      field referencing the body part, then the UAC sets the message-
      body to the body.
   o  However, if solely one body needs to be transported in a SIP
      message field, and the UAC needs
   how to include in the SIP message refer a SIP
      header field referencing the body part, then the UAC sets the complete message-body to be of the "multipart" MIME type and includes one
      body part and associated using a Content-ID header field. URL.

1.4.  Examples  Consequencies

   The examples below shows the consequencies 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 one body
   content only in the INVITE request.  This body contains the location information and content can be e.g. of the
   application/pidf+xml MIME type.

   However, due to [RFC6442] requiring inclusion of a Geolocation header
   field referencing referring the body part containing with the location information, the UAC needs to include
   includes a multipart message-body of "multipart/mixed" MIME
   type with single body part in the INVITE
   request, and includes the UAC needs to include a body part location information of the application/pidf+xml application/
   pidf+xml MIME type and an associated Content-ID header field in the message-body of the "multipart/mixed" MIME type.
   body part.

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 content
   only in the REFER request.  This body contains the list of targets and content is of the application/
   resource-lists+xml MIME type.

   However, due to [RFC5368] requiring inclusion of a Refer-To header
   field referencing referring the body part containing the list of targets, the UAC needs to include
   includes a multipart message-body of the "multipart/mixed" MIME
   type with single body part in the REFER request
   request, and includes the UAC needs to include a body part list of
   the application/resource-lists+xml targets of application/resource-
   lists+xml MIME type and an associated Content-
   ID Content-ID header field in the message-body of the "multipart/mixed" MIME
   type.
   body part.

1.5.  Solution

   To avoid the unnecessary usage of a message-body of a "multipart"
   MIME type when only one body needs

   In order to be included in a SIP message, solve the problems described above, this document specifies a document:

   o  Specifies and registers the 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 MIME-Version header field, if included in the header fields of
      the SIP message;
   o  a Content-Disposition header field, if included in the header
      fields of the SIP message;
   o  a Content-Encoding header field, if included in the header fields
      of the SIP message;
   o  a Content-ID header field, if included in the header fields of the
      SIP message;
   o  a Content-Language header field, if included in the header fields
      of the SIP message; field; and
   o  Specifies that, when used as a Content-Length SIP header field, if included in the Content-ID
      header fields 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-Type header field, if included in the Content-ID URL to refer a complete
      message-body and metadata provided by some additional SIP header fields of
      fields.

   NOTE: In [RFC5621], the SIP message. Content-ID URL refers 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.

3.2.  Syntax

   The ABNF for the Content-ID header fields is:

      Content-ID = "Content-ID" HCOLON msg-id

   NOTE:

      msg-id is     = "<" id-left "@" id-right ">"

      NOTE: id-left and id-right are specified in [RFC5322].

      NOTE: When used in a SIP header field, the msg-id syntax has been
      simplified compared to the syntax in [RFC5322].

3.3.  Semantic

   A  Semantics

   The Content-ID header field included in the header fields of a SIP
   message
   indicates a globally unique identification of a body part consisting
   of identifies the message-body of the SIP message and: message, and the
   metadata provided by:

   o  a MIME-Version header field, if included in  the Content-ID header fields of
      the SIP message; field itself;
   o  a Content-Disposition MIME-Version header field, if included in the header fields of
      the SIP message;
   o  a Content-Encoding Content-Disposition header field, if included in the header
      fields of the SIP message;
   o  a Content-ID Content-Encoding header field, if included in the header fields
      of the SIP message;
   o  a Content-Language header field, if included in the header fields
      of the SIP message;
   o  a Content-Length header field, if included in the header fields of
      the SIP message; and
   o  a Content-Type header field, if 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 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.

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 to reference to a body part.A

 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 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 is an
   encrypted content, body, it MUST NOT be possible to derive a key that can be
   used to decrypt the message-body content body from the Content-ID header field value.

5.

6.  IANA Considerations considerations

   This specification registers a new SIP header field according to the
   procedures in [RFC3261].

5.1.

6.1.  Header Field 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.

7.  Change Log log

   [RFC EDITOR NOTE: Please remove this section when publishing]

   Changes in draft-ietf-sipcore-content-id-01:

   o  Clean up of section 1, including shortening introduction and
      cleaning up of "body" and "body part" usages. from draft-ietf-sipcore-content-id-01

   o  Clarify that the SIP header fields forming the body part are not
      required  Update to be present in the SIP message. RFC 5621 added.
   o  MIME-Version header field included as one of the SIP header fields
      forming the body part;

7.  Editorial changes.

8.  Normative References 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>.

   [RFC2046]  Freed, N. and N. Borenstein, "Multipurpose Internet Mail
              Extensions (MIME) Part Two: Media Types", RFC 2046,
              DOI 10.17487/RFC2046, November 1996,
              <http://www.rfc-editor.org/info/rfc2046>.

   [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

   Ivo Sedlacek
   Ericsson
   Sokolovska 79
   Praha  18600
   Czech Republic

   Email: ivo.sedlacek@ericsson.com