SIPCORE Working Group C. Holmberg Internet-Draft I. Sedlacek Updates: 5621 (if approved) Ericsson Intended status: Standards Track June 5, 2017 Expires: December 7, 2017 Content-ID header field in Session Initiation Protocol (SIP) draft-ietf-sipcore-content-id-06 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 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 Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet- Drafts is at http://datatracker.ietf.org/drafts/current/. 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Holmberg & Sedlacek Expires December 7, 2017 [Page 1] Internet-Draft Content-ID in SIP June 2017 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 3.4.3. Example . . . . . . . . . . . . . . . . . . . . . . . 6 4. Update to RFC 5621 . . . . . . . . . . . . . . . . . . . . . 7 5. Security considerations . . . . . . . . . . . . . . . . . . . 8 6. IANA considerations . . . . . . . . . . . . . . . . . . . . . 8 6.1. Header field . . . . . . . . . . . . . . . . . . . . . . 8 7. Change log . . . . . . . . . . . . . . . . . . . . . . . . . 9 8. Normative references . . . . . . . . . . . . . . . . . . . . 9 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 10 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 Holmberg & Sedlacek Expires December 7, 2017 [Page 2] Internet-Draft Content-ID in SIP June 2017 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. NOTE: In [RFC5621], the Content-ID URL references a specific body part only. 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 MIME entity 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/ Holmberg & Sedlacek Expires December 7, 2017 [Page 3] Internet-Draft Content-ID in SIP June 2017 pidf+xml MIME type and an associated Content-ID header field in the 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 only one MIME entity in the REFER request. This MIME entity 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. 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. Holmberg & Sedlacek Expires December 7, 2017 [Page 4] Internet-Draft Content-ID in SIP June 2017 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], to disallow the use of comments and to adopt to the SIP usage of leading white space. The value of 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. 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. Holmberg & Sedlacek Expires December 7, 2017 [Page 5] Internet-Draft Content-ID in SIP June 2017 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. 3.4.3. Example The figure shows an example from [RFC5368], where the SIP Content-ID header field is used to reference the message body (non-multipart) of a SIP message. Holmberg & Sedlacek Expires December 7, 2017 [Page 6] Internet-Draft Content-ID in SIP June 2017 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" From: Carol ;tag=32331 Call-ID: d432fa84b4c76e66710 CSeq: 2 REFER Contact: Refer-To: 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: 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. Holmberg & Sedlacek Expires December 7, 2017 [Page 7] Internet-Draft Content-ID in SIP June 2017 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]. 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 Holmberg & Sedlacek Expires December 7, 2017 [Page 8] Internet-Draft Content-ID in SIP June 2017 7. Change log [RFC EDITOR NOTE: Please remove this section when publishing] Changes from draft-ietf-sipcore-content-id-05 o Changes based on AD comments from Ben Campell: o - Clarifying that Content-ID header field value is unique within the scope of a SIP message. Changes from draft-ietf-sipcore-content-id-04 o Minor editorial fix. Changes from draft-ietf-sipcore-content-id-03 o Changes based on doc shepard review: o - Reference to RFC 5234 added. o - SIP message example 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, . [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997, . [RFC2392] Levinson, E., "Content-ID and Message-ID Uniform Resource Locators", RFC 2392, DOI 10.17487/RFC2392, August 1998, . Holmberg & Sedlacek Expires December 7, 2017 [Page 9] Internet-Draft Content-ID in SIP June 2017 [RFC5234] Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax Specifications: ABNF", STD 68, RFC 5234, DOI 10.17487/RFC5234, January 2008, . [RFC5322] Resnick, P., Ed., "Internet Message Format", RFC 5322, DOI 10.17487/RFC5322, October 2008, . [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, . [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, . [RFC5621] Camarillo, G., "Message Body Handling in the Session Initiation Protocol (SIP)", RFC 5621, DOI 10.17487/RFC5621, September 2009, . [RFC6442] Polk, J., Rosen, B., and J. Peterson, "Location Conveyance for the Session Initiation Protocol", RFC 6442, DOI 10.17487/RFC6442, December 2011, . Authors' Addresses Christer Holmberg Ericsson Hirsalantie 11 Jorvas 02420 Finland Email: christer.holmberg@ericsson.com Holmberg & Sedlacek Expires December 7, 2017 [Page 10] Internet-Draft Content-ID in SIP June 2017 Ivo Sedlacek Ericsson Sokolovska 79 Praha 18600 Czech Republic Email: ivo.sedlacek@ericsson.com Holmberg & Sedlacek Expires December 7, 2017 [Page 11]