Network Working Group                                            D. Wing
Request for Comments: 2530                                 Cisco Systems
Category: Standards Track                                     March 1999


              Indicating Supported Media Features Using
                      Extensions to DSN and MDN

Status of this Memo

  This document specifies an Internet standards track protocol for the
  Internet community, and requests discussion and suggestions for
  improvements.  Please refer to the current edition of the "Internet
  Official Protocol Standards" (STD 1) for the standardization state
  and status of this protocol.  Distribution of this memo is unlimited.

Copyright Notice

  Copyright (C) The Internet Society (1999).  All Rights Reserved.

1.  Abstract

  There is a need in Internet mail and Internet fax for a recipient to
  indicate the media features it supports so that messages can be
  generated by senders without exceeding the recipient's abilities.

  This memo describes a format for generating Message Disposition
  Notifications [RFC2298] and Delivery Status Notifications [RFC1894]
  which contain such information.  This information can be used by
  senders to avoid exceeding the recipient's capabilities when sending
  subsequent messages.

2. Introduction

  The extensions described in this document can be used in Message
  Disposition Notifications [RFC2298] or Delivery Status Notifications
  [RFC1894], as appropriate for the implementation.

  Note that both DSNs and MDNs have drawbacks: DSNs are not available
  between all senders and receivers, and MDNs require the receiver to
  disclose message disposition information (or, if using the "denied"
  disposition-type, the time the disposition notification was
  generated).

  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].




Wing                        Standards Track                     [Page 1]

RFC 2530            Media Features using DSN and MDN          March 1999


3.  Extensions for use by DSN and MDN

  The following extension is available to both DSN [RFC1894] and MDN
  [RFC2298] messages.

  For a DSN message, the following per-recipient fields are defined
  (section 2.3 of [RFC1894]).  For an MDN message, the following
  extension fields are defined (section 3.1 of [RFC2298]).  Using the
  language of [RFC2234]:

     extension-field    = media-features CRLF

     media-features     = "Media-Accept-Features" ":"
                           media-feature-tags
     media-feature-tags = <*text as defined below,
                           with LWSP wrapping>

  The <media-feature-tags> are defined in separate schema documents
  which MUST utilize the language described in [SYNTAX].  The schema
  MUST be registered following the registration requirements of
  [RFC2506].

3.1.  Examples

  The following examples assume there is a schema document which
  defines the tags shown.

3.1.1.  Paper-size and Color

  Assuming there is a schema document which describes the tags paper-
  size and color, the following example is valid:

     Media-Accept-Features: (& (paper-size=a4) (color=binary) )

3.1.2.  UA-Media, Paper-size, and Color

  Assuming there is a schema document which describes the tags paper-
  size, color, and grey:

     Media-Accept-Features: (& (| (paper-size=a4) (paper-size=letter) )
       (| (& (color=grey) (dpi=200) (dpi-xyratio=200/100) )
       (& (color=limited) (dpi=200) (dpi-xy=200/100) ) )

4.  MTA Implmentation Recommendation

  If the recipient's MTA determines that a message cannot be processed,
  the recipient's MTA is strongly encouraged to reject the message with
  a status code of 5.6.1 [RFC1893].  This status code may be returned



Wing                        Standards Track                     [Page 2]

RFC 2530            Media Features using DSN and MDN          March 1999


  in response to the end-of-mail-data indicator if the MTA supports
  reporting of enhanced error codes [RFC2034], or after message
  reception by generating a delivery failure DSN ("bounce").

5.  Security Considerations

  Inaccurate media feature information could cause a denial of service,
  causing subsequent messages to be sent which the recipient is unable
  to process.

  The media feature information could be inaccurate due to a malicious
  attack (spoofed DSN or MDN) or misconfiguration.

6.  Acknowledgments

  The author thanks the members of the Internet Fax working group for
  assistance with this document, and especially Larry Masinter, Graham
  Klyne, and Ned Freed.

7.  References

  [RFC2506] Holtman, K., Mutz, A. and T. Hardie, "Media Feature Tag
            Registration Procedure", BCP 31, RFC 2506, March 1999.

  [RFC1894] Moore, K. and G. Vaudreuil, "An Extensible Message Format
            for Delivery Status Notifications", RFC 1894, January 1996.

  [RFC2034] Freed, N., "SMTP Service Extension for Returning Enhanced
            Error Codes", RFC 2034, October 1996.

  [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
            Requirement Levels", BCP 14, RFC 2119, March 1997.

  [RFC2234] Crocker, D. and P. Overell, "Augmented BNF for Syntax
            Specifications:  ABNF", RFC 2234, November 1997.

  [RFC2298] Fajman, R., "An Extensible Message Format for Message
            Disposition Notifications", RFC 2298, March 1998.

  [SYNTAX]  Klyne, G., "A Syntax for Describing Media Feature Sets",
            RFC 2533, March 1999.










Wing                        Standards Track                     [Page 3]

RFC 2530            Media Features using DSN and MDN          March 1999


8.  Author's Address

  Dan Wing
  Cisco Systems, Inc.
  101 Cooper Street
  Santa Cruz, CA 95060  USA

  Phone: +1 831 457 5200
  Fax:   +1 831 457 5208
  EMail: [email protected]









































Wing                        Standards Track                     [Page 4]

RFC 2530            Media Features using DSN and MDN          March 1999


9.  Full Copyright Statement

  Copyright (C) The Internet Society (1999).  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 assigns.

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
























Wing                        Standards Track                     [Page 5]


You are viewing proxied material from gopher.fnord.one. The copyright of proxied material belongs to its original authors. Any comments or complaints in relation to proxied material should be directed to the original authors of the content concerned. Please see the disclaimer for more details.