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'CONNEG-REG' ** Obsolete normative reference: RFC 1894 (Obsoleted by RFC 3464) ** Obsolete normative reference: RFC 2234 (Obsoleted by RFC 4234) ** Obsolete normative reference: RFC 2298 (Obsoleted by RFC 3798) -- No information found for draft-ietf-conneg-feature-syntax-XX - is the name correct? -- Possible downref: Normative reference to a draft: ref. 'SYNTAX' Summary: 13 errors (**), 0 flaws (~~), 4 warnings (==), 6 comments (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Fax Working Group Dan Wing 3 Internet Draft Cisco Systems 4 January 28, 1999 5 Expires June 1999 6 draft-ietf-fax-reporting-extensions-05.txt 8 Indicating Supported Media Features Using 9 Extensions to DSN and MDN 11 Status of this memo 13 This document is an Internet-Draft. Internet-Drafts are working 14 documents of the Internet Engineering Task Force (IETF), its areas, 15 and its working groups. Note that other groups may also distribute 16 working documents as Internet-Drafts. 18 Internet-Drafts are draft documents valid for a maximum of six months 19 and may be updated, replaced, or obsoleted by other documents at any 20 time. It is inappropriate to use Internet-Drafts as reference 21 material or to cite them other than as "work in progress." 23 To view the entire list of current Internet-Drafts, please check 24 the "1id-abstracts.txt" listing contained in the Internet-Drafts 25 Shadow Directories on ftp.is.co.za (Africa), ftp.nordu.net 26 (Northern Europe), ftp.nis.garr.it (Southern Europe), munnari.oz.au 27 (Pacific Rim), ftp.ietf.org (US East Coast), or ftp.isi.edu 28 (US West Coast). 30 Copyright Notice 32 Copyright (C) The Internet Society (1999). All Rights Reserved. 34 1. Abstract 36 There is a need in Internet mail and Internet fax for a recipient to 37 indicate the media features it supports so that messages can be 38 generated by senders without exceeding the recipient's abilities. 40 This memo describes a format for generating Message Disposition 41 Notifications [RFC2298] and Delivery Status Notifications [RFC1894] 42 which contain such information. This information can be used by 43 senders to avoid exceeding the recipient's capabilities when sending 44 subsequent messages. 46 2. Introduction 48 The extensions described in this document can be used in Message 49 Disposition Notifications [RFC2298] or Delivery Status Notifications 51 [RFC1894], as appropriate for the implementation. 53 Note that both DSNs and MDNs have drawbacks: DSNs are not available 54 between all senders and receivers, and MDNs require the receiver to 55 disclose message disposition information (or, if using the "denied" 56 disposition-type, the time the disposition notification was 57 generated). 59 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 60 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 61 document are to be interpreted as described in [RFC2119]. 63 3. Extensions for use by DSN and MDN 65 The following extension is available to both DSN [RFC1894] and MDN 66 [RFC2298] messages. 68 For a DSN message, the following per-recipient fields are defined 69 (section 2.3 of [RFC1894]). For an MDN message, the following 70 extension fields are defined (section 3.1 of [RFC2298]). Using 71 the language of [RFC2234]: 73 extension-field = media-features CRLF 75 media-features = "Media-Accept-Features" ":" 76 media-feature-tags 77 media-feature-tags = <*text as defined below, 78 with LWSP wrapping> 80 The are defined in separate schema documents 81 which MUST utilize the language described in [SYNTAX]. The 82 schema MUST be registered following the registration requirements 83 of [CONNEG-REG]. 85 3.1. Examples 87 The following examples assume there is a schema document 88 which defines the tags shown. 90 3.1.1. Paper-size and Color 92 Assuming there is a schema document which describes the 93 tags paper-size and color, the following example is valid: 95 Media-Accept-Features: (& (paper-size=a4) (color=binary) ) 97 3.1.2. UA-Media, Paper-size, and Color 98 Assuming there is a schema document which describes the 99 tags paper-size, color, and grey: 101 Media-Accept-Features: (& (| (paper-size=a4) (paper-size=letter) ) 102 (| (& (color=grey) (dpi=200) (dpi-xyratio=200/100) ) 103 (& (color=limited) (dpi=200) (dpi-xy=200/100) ) ) 105 4. MTA Implmentation Recommendation 107 If the recipient's MTA determines that a message cannot be processed, 108 the recipient's MTA is strongly encouraged to reject the message with 109 a status code of 5.6.1 [RFC1893]. This status code may be returned 110 in response to the end-of-mail-data indicator if the MTA supports 111 reporting of enhanced error codes [RFC2034], or after message 112 reception by generating a delivery failure DSN ("bounce"). 114 5. Security Considerations 116 Inaccurate media feature information could cause a denial of service, 117 causing subsequent messages to be sent which the recipient is 118 unable to process. 120 The media feature information could be inaccurate due to a malicious 121 attack (spoofed DSN or MDN) or misconfiguration. 123 6. Acknowledgments 125 The author thanks the members of the Internet Fax working group for 126 assistance with this document, and especially Larry Masinter, 127 Graham Klyne, and Ned Freed. 129 7. References 131 [CONNEG-REG] K. Holtman, A. Mutz, T. Hardie, "Media Feature Tag 132 Registration Procedure", Internet Draft, Work in Progress, 133 draft-ietf-conneg-feature-reg-XX.txt. 135 [RFC1894] K. Moore, G. Vaudreuil, "An Extensible Message Format for 136 Delivery Status Notifications", RFC 1894, January 1996. 138 [RFC2034] N. Freed, "SMTP Service Extension for Returning Enhanced 139 Error Codes", RFC 2034, October 1996. 141 [RFC2119] S. Bradner, "Key words for use in RFCs to Indicate 142 Requirement Levels", RFC 2119, March 1997. 144 [RFC2234] D. Crocker, P. Overell, "Augmented BNF for Syntax 145 Specifications: ABNF", RFC 2234, November 1997. 147 [RFC2298] R. Fajman, "An Extensible Message Format for Message 148 Disposition Notifications", RFC 2298, March 1998. 150 [SYNTAX] G. Klyne, "A syntax for describing media feature sets", 151 Internet Draft, Work in Progress, 152 draft-ietf-conneg-feature-syntax-XX.txt. 154 8. Author's Address 156 Dan Wing 157 Cisco Systems, Inc. 158 101 Cooper Street 159 Santa Cruz, CA 95060 USA 161 Phone: +1 831 457 5200 162 Fax: +1 831 457 5208 163 EMail: dwing@cisco.com 165 9. Copyright 167 Copyright (C) The Internet Society 1999. All Rights Reserved. 169 This document and translations of it may be copied and furnished to 170 others, and derivative works that comment on or otherwise explain it 171 or assist in its implmentation may be prepared, copied, published and 172 distributed, in whole or in part, without restriction of any kind, 173 provided that the above copyright notice and this paragraph are 174 included on all such copies and derivative works. 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