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IETF RFC 2530

Indicating Supported Media Features Using Extensions to DSN and MDN

Last modified on Thursday, March 11th, 1999

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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 © 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 [RFC 2298] and Delivery Status Notifications [RFC 1894]
   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 [RFC 2298] or Delivery Status Notifications
   [RFC 1894], 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 [RFC 2119].




Wing                        Standards Track                  PAGE 1 top


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 [RFC 1894] and MDN [RFC 2298] messages. For a DSN message, the following per-recipient fields are defined (section 2.3 of [RFC 1894]). For an MDN message, the following extension fields are defined (section 3.1 of [RFC 2298]). Using the language of [RFC 2234]: 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 [RFC 2506]. 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 [RFC 1893]. This status code may be returned Wing Standards Track PAGE 2 top

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 [RFC 2034], 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 [RFC 2506] Holtman, K., Mutz, A. and T. Hardie, "Media Feature Tag Registration Procedure", BCP 31, RFC 2506, March 1999. [RFC 1894] Moore, K. and G. Vaudreuil, "An Extensible Message Format for Delivery Status Notifications", RFC 1894, January 1996. [RFC 2034] Freed, N., "SMTP Service Extension for Returning Enhanced Error Codes", RFC 2034, October 1996. [RFC 2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [RFC 2234] Crocker, D. and P. Overell, "Augmented BNF for Syntax Specifications: ABNF", RFC 2234, November 1997. [RFC 2298] 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 top

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: dwing@cisco.com Wing Standards Track PAGE 4 top

RFC 2530 Media Features using DSN and MDN March 1999 9. Full Copyright Statement Copyright © 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 top

Indicating Supported Media Features Using Extensions to DSN and MDN RFC TOTAL SIZE: 7824 bytes PUBLICATION DATE: Thursday, March 11th, 1999 LEGAL RIGHTS: The IETF Trust (see BCP 78)


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