Indicating Supported Media Features Using Extensions to DSN and MDN
RFC 2530
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RFC - Proposed Standard
(March 1999; No errata)
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Author |
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Dan Wing
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Last updated |
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2013-03-02
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IETF
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RFC 2530 (Proposed Standard)
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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 (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
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