One document matched: draft-jennings-sip-mime-00.txt

SIP WG                                                       C. Jennings
Internet-Draft                                             Cisco Systems
Expires: December 21, 2003                                 June 22, 2003


            Recommendations for using MIME body parts in SIP
                       draft-jennings-sip-mime-00

Status of this Memo

   This document is an Internet-Draft and is in full conformance with
   all provisions of Section 10 of RFC2026.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF), its areas, and its working groups. Note that other
   groups may also distribute working documents as Internet-Drafts.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time. It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   The list of current Internet-Drafts can be accessed at http://
   www.ietf.org/ietf/1id-abstracts.txt.

   The list of Internet-Draft Shadow Directories can be accessed at
   http://www.ietf.org/shadow.html.

   This Internet-Draft will expire on December 21, 2003.

Copyright Notice

   Copyright (C) The Internet Society (2003). All Rights Reserved.

Abstract

   This document describes conventions for using MIME body parts in SIP
   messages. It uses a transport encoding of "binary" since SIP messages
   are always passed over an 8bit clean transport.

1. 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 RFC-2119 [2].

   This document adopts the terminology defined in RFC 2045 [1],
   particularly for the terms "transport encoding" and "binary".




Jennings               Expires December 21, 2003                [Page 1]

Internet-Draft                MIME in SIP                      June 2003


2. Introduction

   The Session Initiation Protocol (SIP) [3] protocol makes use of MIME
   [1] body parts. MIME provides several alternatives that were required
   given the characteristics of existing mail transport protocols and
   mail gateways that MIME operates through. SIP is always transported
   over an 8bit safe transport and thus does not need all the options
   available. This draft clarifies what should be used in the SIP
   context.

3. Discussion

   MIME offers several transport encoding options and any of them will
   work in SIP. However, having several options where one is needed does
   not contribute to interoperability. Binary encoding is faster to
   encode and decode, requires less code, and results in smaller
   messages than the other options. There has been a practice in the
   published SIP examples of using a base64 encoding due to the ease of
   displaying the example in publication. Some SIP implementers have
   taken this to mean that this is the preferred encoding and as a
   result only work with base64. Given the need to improve
   interoperability, it is reasonable to suggest that SIP
   implementations send one type of encoding.

   There are situations in which the body from a SIP message might be
   passed to another non SIP transport that might expose additional
   limitations.  Currently the only example of this is the transfer of
   bodies from instant messaging messages to other instant messaging
   systems.  Since other instant messaging protocols are also 8bit
   clean, gateways from SIP instant messaging [5] to these other
   protocols do not have this problem.  Gateways to other protocols (for
   example SMTP [4]) need to modify the content of these messages
   anyway, regardless of the MIME encoding which is used on the original
   message.

4. Recommendations

   Devices MUST use a content transfer encoding of "binary" for MIME
   body parts in SIP messages they send.

5. Security Considerations

   This document limits options that exist in RFC 3261 so it does not
   introduce any additional security concerns beyond what is in RFC
   3261.

6. Open Issues




Jennings               Expires December 21, 2003                [Page 2]

Internet-Draft                MIME in SIP                      June 2003


   Should we bother to do this or just write it up as a bug on RFC 3261?

Normative References

   [1]  Freed, N. and N. Borenstein, "Multipurpose Internet Mail
        Extensions (MIME) Part One: Format of Internet Message Bodies",
        RFC 2045, November 1996.

   [2]  Bradner, S., "Key words for use in RFCs to Indicate Requirement
        Levels", BCP 14, RFC 2119, March 1997.

   [3]  Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston, A.,
        Peterson, J., Sparks, R., Handley, M. and E. Schooler, "SIP:
        Session Initiation Protocol", RFC 3261, June 2002.

Informative References

   [4]  Klensin, J., "Simple Mail Transfer Protocol", RFC 2821, April
        2001.

   [5]  Campbell, B., Rosenberg, J., Schulzrinne, H., Huitema, C. and D.
        Gurle, "Session Initiation Protocol (SIP) Extension for Instant
        Messaging", RFC 3428, December 2002.


Author's Address

   Cullen Jennings
   Cisco Systems
   170 West Tasman Drive
   MS: SJC-21/3
   San Jose, CA  95134
   USA

   Phone: +1 408 527-9132
   EMail: fluffy@cisco.com















Jennings               Expires December 21, 2003                [Page 3]

Internet-Draft                MIME in SIP                      June 2003


Intellectual Property Statement

   The IETF takes no position regarding the validity or scope of any
   intellectual property or other rights that might be claimed to
   pertain to the implementation or use of the technology described in
   this document or the extent to which any license under such rights
   might or might not be available; neither does it represent that it
   has made any effort to identify any such rights. Information on the
   IETF's procedures with respect to rights in standards-track and
   standards-related documentation can be found in BCP-11. Copies of
   claims of rights made available for publication and any assurances of
   licenses to be made available, or the result of an attempt made to
   obtain a general license or permission for the use of such
   proprietary rights by implementors or users of this specification can
   be obtained from the IETF Secretariat.

   The IETF invites any interested party to bring to its attention any
   copyrights, patents or patent applications, or other proprietary
   rights which may cover technology that may be required to practice
   this standard. Please address the information to the IETF Executive
   Director.


Full Copyright Statement

   Copyright (C) The Internet Society (2003). All Rights Reserved.

   This document and translations of it may be copied and furnished to
   others, and derivative works that comment on or otherwise explain it
   or assist in its implementation may be prepared, copied, published
   and distributed, in whole or in part, without restriction of any
   kind, provided that the above copyright notice and this paragraph are
   included on all such copies and derivative works. However, this
   document itself may not be modified in any way, such as by removing
   the copyright notice or references to the Internet Society or other
   Internet organizations, except as needed for the purpose of
   developing Internet standards in which case the procedures for
   copyrights defined in the Internet Standards process must be
   followed, or as required to translate it into languages other than
   English.

   The limited permissions granted above are perpetual and will not be
   revoked by the Internet Society or its successors or assignees.

   This document and the information contained herein is provided on an
   "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
   TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
   BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION



Jennings               Expires December 21, 2003                [Page 4]

Internet-Draft                MIME in SIP                      June 2003


   HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
   MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.


Acknowledgement

   Funding for the RFC Editor function is currently provided by the
   Internet Society.











































Jennings               Expires December 21, 2003                [Page 5]