One document matched: draft-jennings-sip-mime-02.txt

Differences from draft-jennings-sip-mime-01.txt

SIP WG                                                       C. Jennings
Internet-Draft                                             Cisco Systems
Expires: January 14, 2005                                  July 16, 2004


            Recommendations for using MIME body parts in SIP
                       draft-jennings-sip-mime-02

Status of this Memo

   By submitting this Internet-Draft, I certify that any applicable
   patent or other IPR claims of which I am aware have been disclosed,
   and any of which I become aware will be disclosed, in accordance with
   RFC 3668.

   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 January 14, 2005.

Copyright Notice

   Copyright (C) The Internet Society (2004).  All Rights Reserved.

Abstract

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

   This work is being discussed on the sip@ietf.org mailing list.

1.  Conventions

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this



Jennings                Expires January 14, 2005                [Page 1]

Internet-Draft                MIME in SIP                      July 2004


   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".

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 examples 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.  There is no need to receive
   messages that do not have an encoding of "binary".  This will be
   documented in an errata of RFC 3261.

   The above recommendation was the consensus of the room at the



Jennings                Expires January 14, 2005                [Page 2]

Internet-Draft                MIME in SIP                      July 2004


   previous meeting.

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.  References

6.1  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.

6.2  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-21/2
   San Jose, CA  95134
   USA

   Phone: +1 408 902-3341
   EMail: fluffy@cisco.com







Jennings                Expires January 14, 2005                [Page 3]

Internet-Draft                MIME in SIP                      July 2004


Intellectual Property Statement

   The IETF takes no position regarding the validity or scope of any
   Intellectual Property Rights 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; nor does it represent that it has
   made any independent effort to identify any such rights.  Information
   on the procedures with respect to rights in RFC documents can be
   found in BCP 78 and BCP 79.

   Copies of IPR disclosures made to the IETF Secretariat 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 implementers or users of this
   specification can be obtained from the IETF on-line IPR repository at
   http://www.ietf.org/ipr.

   The IETF invites any interested party to bring to its attention any
   copyrights, patents or patent applications, or other proprietary
   rights that may cover technology that may be required to implement
   this standard.  Please address the information to the IETF at
   ietf-ipr@ietf.org.


Disclaimer of Validity

   This document and the information contained herein are provided on an
   "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
   OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET
   ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED,
   INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE
   INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
   WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.


Copyright Statement

   Copyright (C) The Internet Society (2004).  This document is subject
   to the rights, licenses and restrictions contained in BCP 78, and
   except as set forth therein, the authors retain all their rights.


Acknowledgment

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




Jennings                Expires January 14, 2005                [Page 4]