SIPCORE Working Group                                        C. Holmberg
Internet-Draft                                               I. Sedlacek
Intended status: Standards Track                                Ericsson
Expires: August 3, September 9, 2017                                 January 30,                                 March 8, 2017

      Content ID header field in Session Initiation Protocol (SIP)
                    draft-ietf-sipcore-content-id-00
                    draft-ietf-sipcore-content-id-01

Abstract

   This document specifies the Content-ID header field for usage in the
   Session Initiation Protocol (SIP).

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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   5
   3.  Content-ID header field . . . . . . . . . . . . . . . . . . .   5
     3.1.  Introduction  . . . . . . . . . . . . . . . . . . . . . .   5
     3.2.  Syntax  . . . . . . . . . . . . . . . . . . . . . . . . .   5
     3.3.  Semantic  . . . . . . . . . . . . . . . . . . . . . . . .   5
     3.4.  Procedures  . . . . . . . . . . . . . . . . . . . . . . .   5   6
       3.4.1.  UA procedures . . . . . . . . . . . . . . . . . . . .   5   6
       3.4.2.  Proxy procedures  . . . . . . . . . . . . . . . . . .   6
   4.  Security Considerations . . . . . . . . . . . . . . . . . . .   6
   5.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   6
     5.1.  Header Field  . . . . . . . . . . . . . . . . . . . . . .   6
   6.  Change Log  . . . . . . . . . . . . . . . . . . . . . . . . .   6   7
   7.  Normative References  . . . . . . . . . . . . . . . . . . . .   6   7
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   7   8

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, parts, as specified in [RFC3261] and [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 is no body parts and part specified.  Thus, 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
   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  If solely one body needs to be transported in a SIP message, if
      a message and
      the UAC does not need to include in the SIP message a SIP header
      field referencing the body part, then the UAC sets the message-body message-
      body to the body.
   o  However, when if solely one body needs to be transported in a SIP
      message, if a
      message and the 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 to be of the "multipart" MIME type 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.

   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 "multipart/mixed" MIME
   type in the INVITE request, and the UAC needs to include a body part with
   of the application/pidf+xml body MIME type and associated Content-
   ID Content-ID
   header field in the multipart/mixed body. message-body of the "multipart/mixed" MIME type.

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 "multipart/mixed" MIME
   type in the REFER request and the UE UAC needs to include a body part with of
   the application/resource-lists+xml body MIME type and associated Content-ID Content-
   ID header field in the multipart/mixed body. message-body of the "multipart/mixed" MIME
   type.

1.5.  Solution

   To avoid the unnecessary usage of the [RFC2045] format a message-body of a "multipart"
   MIME type 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 MIME-Version header field, if included in the header fields of
      the SIP message;
   o  a Content-Disposition header field; field, if included in the header
      fields of the SIP message;
   o  a Content-Encoding header field; field, if included in the header fields
      of the SIP message;
   o  a Content-Language Content-ID header field, if included in the header field; fields of the
      SIP message;
   o  a Content-Length Content-Language header field, if included in the header field; fields
      of the SIP message;
   o  a Content-Type Content-Length header field; and field, if included in the header fields of
      the SIP message;
   o  a Content-ID Content-Type header field; field, if 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].

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

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

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>.

   [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