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'SUBMIT' Summary: 17 errors (**), 0 flaws (~~), 8 warnings (==), 10 comments (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Internet Fax Working Group Larry Masinter 3 Internet Draft Xerox Corporation 4 January 27, 1999 Dan Wing 5 Expires June 1999 Cisco Systems 6 draft-ietf-fax-eifax-12.txt 8 Extended Facsimile Using Internet Mail 10 Status of this memo 12 This document is an Internet-Draft. Internet-Drafts are working 13 documents of the Internet Engineering Task Force (IETF), its areas, 14 and its working groups. Note that other groups may also distribute 15 working documents as Internet-Drafts. 17 Internet-Drafts are draft documents valid for a maximum of six months 18 and may be updated, replaced, or obsoleted by other documents at any 19 time. It is inappropriate to use Internet-Drafts as reference 20 material or to cite them other than as "work in progress." 22 To view the entire list of current Internet-Drafts, please check 23 the "1id-abstracts.txt" listing contained in the Internet-Drafts 24 Shadow Directories on ftp.is.co.za (Africa), ftp.nordu.net 25 (Northern Europe), ftp.nis.garr.it (Southern Europe), munnari.oz.au 26 (Pacific Rim), ftp.ietf.org (US East Coast), or ftp.isi.edu 27 (US West Coast). 29 This draft is a product of the IETF Internet Fax working group. To 30 subscribe to the mailing list, send a message to 31 ietf-fax-request@imc.org with the line "subscribe" in the body of the 32 message. Archives are available from . 34 Copyright Notice 36 Copyright (C) The Internet Society (1999). All Rights Reserved. 38 Abstract 40 This document describes extensions to "Simple Mode of Facsimile Using 41 Internet Mail" [RFC2305] and describes additional features, including 42 transmission of enhanced document characteristics (higher resolution, 43 color) and confirmation of delivery and processing. 45 These additional features are designed to provide the highest level 46 of interoperability with the existing and future standards-compliant 47 email infrastructure and mail user agents, while providing a level of 48 service that approximates the level currently enjoyed by fax users. 50 The IETF has been notified of intellectual property rights claimed in 51 regard to some or all of the specification contained in this 52 document. For more information consult the online list of claimed 53 rights in . 55 1. Introduction 57 This document notes a number of enhancements to the "Simple Mode of 58 Facsimile Using Internet Mail" [RFC2305] that may be combined to 59 create an extended mode of facsimile using Internet mail. 61 The new features are designed to be interoperable with the existing 62 base of mail transfer agents (MTAs) and mail user agents (MUAs), 63 and take advantage of existing standards for advanced functionality 64 such as positive delivery confirmation and disposition notification. 65 The enhancements described in this document utilize the messaging 66 infrastructure, where possible, instead of creating fax-specific 67 features which are unlikely to be implemented in non-fax messaging 68 software. 70 This document standardizes the following two features. 72 * Delivery confirmation (Section 2) (required) 73 * Additional document features (Section 3) (optional) 75 These features are fully described in another document titled 76 "Terminology and Goals for Internet Fax". 78 1.1. Definition of Terms 80 The term "processing" indicates the action of rendering or 81 transmitting the contents of the message to a printer, display device, 82 or fax machine. 84 The term "processing confirmation" is an indication by the 85 recipient of a message that it is able to process the contents 86 of that message. 88 The term "recipient" indicates the device which performs the 89 processing function. For example, a recipient could be implemented 90 as a traditional Mail User Agent on a PC, a standalone device which 91 retrieves mail using POP3 or IMAP, an SMTP server which prints 92 incoming messages (similar to an LPR server). 94 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 95 "SHOULD", SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 96 document are to be interpreted as described in [RFC2119]. 98 1.2. GSTN Fax Gateways ("onramp"/"offramp") 100 The behavior of gateways from GSTN fax to SMTP ("onramps") and from 101 SMTP to GSTN fax ("offramps") are not described in this document. 102 However, such gateways SHOULD have the behavior characteristics of 103 senders and recipients as described in this document. 105 2. Delivery and Processing Confirmation 107 In traditional GSTN-based realtime facsimile, the receiving terminal 108 acknowledges successful receipt and processing of every page [T.30]. 110 In Internet Mail, the operations of Delivery (to the mailbox) and 111 Disposition (to paper or a screen) may be separated in time (due to 112 store and forwarding of messages) and location (due to separation of 113 delivery agent (MTA) and user agent (MUA)). The confirmation of 114 these two operations are supplied by two different standards-track 115 mechanisms: Delivery Status Notifications (DSN) [RFC1891, RFC1894] 116 and Message Disposition Notifications (MDN) [RFC2298], respectively. 118 This section defines requirements for devices or services that are to 119 be considered compliant with this document. 121 2.1. Sender Requirements 123 Because delivery failure may occur (over disk quota, user no longer 124 exists, malconfigured mailer), a delivery failure message (in the 125 format described by [RFC1894] or otherwise) may be sent to the 126 envelope-from address specified by the sender. Thus, the 127 envelope-from address supplied by the sender MUST be able to properly 128 handle such delivery failure messages. 130 2.1.1. Delivery Confirmation 132 If the sender desires delivery confirmation, the sender MUST request 133 Delivery Status Notification by including the the esmtp-keyword 134 NOTIFY with the esmtp-value SUCCESS [section 5.1 of RFC1891]. 136 2.1.2. Processing Confirmation 138 If the sender desires processing confirmation, the sender MUST 139 request Message Disposition Notification [RFC2298 section 2] 140 when sending the message itself. 142 Because a recipient may silently ignore a request for an MDN [section 143 2.1 of RFC2298] at any time: 144 * MDNs MUST NOT be used for delivery confirmation, but are only 145 useful for disposition ("processing") notification. 147 * the sender MUST NOT assume the recipient will respond to an MDN 148 request in a subsequent message, even if the recipient has 149 done so in the past. 151 The address provided by the sender on the Disposition-Notification-To 152 field MUST be able to receive Message Disposition Notifications 153 messages [RFC2298] and SHOULD be able to receive messages that are 154 not in the Message Disposition Notification format (due to the 155 existence of legacy systems that generate non-RFC2298-compliant 156 responses to the Disposition-Notification-To field). The 157 Disposition-Notification-To address and the envelope-from address 158 SHOULD match to allow automated responses to MDN requests (section 159 2.1 of [RFC2298]). 161 2.2. Recipient Requirements 163 Recipients SHOULD implement Message Disposition Notifications 164 [RFC2298] and SHOULD indicate supported media features in 165 DSN and MDN messages per [REPORT-EXTENSIONS]. 167 If the recipient is an SMTP server, it behaves as part of the 168 receiver infrastructure and is therefore subject to the "Receiver 169 Infrastructure" requirements of this document. 171 See also "Recipient Recommendations" in section 5. 173 2.2.1. MDN Recipient Requirements 175 Recipients MUST be configurable to silently ignore a request for an 176 MDN ([section 2.1 of RFC2298]). 178 If the recipient is an automated message processing system which is 179 not associated with a person, the device MAY be configurable to 180 always respond to MDN requests, but in all cases MUST be configurable 181 to never generate MDNs. 183 A recipient MUST NOT generate an unsolicited MDN to indicate 184 successful processing. A recipient MAY generate an unsolicited MDN 185 (sent to the envelope-from (Return-Path:) address) to indicate 186 processing failure, but subject to the [RFC2298] requirement that it 187 MUST always be possible for an operator to disable unsolicited MDN 188 generation. 190 2.2.2. Recipients Using Mailbox Access Protocols 192 A recipient using [POP3] or [IMAP4] to retrieve its mail MUST NOT 193 generate a Delivery Status Notification message [RFC1894] because 194 such a notification, if it was requested, would have already been 195 issued by the MTA on delivery to the POP3 or IMAP4 message 196 store. 198 The recipient MUST NOT use the RFC822 "To:" fields, "Cc:" fields, 199 "Bcc:" fields, or any other fields containing header recipient 200 information to determine the ultimate destination mailbox or 201 addressee, and SHOULD NOT use other RFC822 or MIME fields for making 202 such determinations. 204 2.3. Messaging Infrastructure Requirements 206 This section explains the requirements of the SMTP messaging 207 infrastructure used by the sender and receiver. This infrastructure 208 is commonly provided by the ISP or a company's internal mailers but 209 can actually be provided by another organization with appropriate 210 service contracts. 212 2.3.1. Sender Infrastructure 214 Support for DSN [RFC1891] MUST be provided by the mail submission 215 server [SUBMIT] used by the sender and MUST be provided up to the 216 mailer responsible for communicating with external (Internet) 217 mailers. 219 Also see section 5.1 of this document. 221 2.3.2. Receiver Infrastructure 223 Support for DSN [RFC1891] MUST be provided by the external 224 (Internet-accessible) mailer, and MUST be provided by each mailer 225 between the external mailer and the recipient. If the recipient is 226 implemented as an SMTP server it MUST also support DSN [RFC1891]. 228 3. Additional Document Capabilities 230 Section 4 of "A Simple Mode of Facsimile Using Internet Mail" 231 [RFC2305] allows sending only the minimum subset of TIFF for 232 Facsimile "unless the sender has prior knowledge of other TIFF fields 233 or values supported by the recipient." 235 A recipient MAY support any or all (or any combination) of the TIFF 236 profiles defined in RFC 2301, in addition to profile S. A recipient 237 which supports additional profiles SHOULD indicate this support as 238 per section 3.2 or 3.3 of this document. As a consequence, a sender 239 MAY use those additional TIFF profiles when sending to a recipient 240 with the corresponding capabilities. 242 A sender SHOULD be able to recognize and process the feature tags as 243 defined in [FAX-SCHEMA] when reviewing the capabilities presented by 244 a potential recipient. The capability matching rules indicated there 245 (by reference to [CONNEG-FEATURE-SYNTAX]) allow for the introduction 246 of new features that may be unrecognized by older implementations. 248 A sender MAY send a message containing both the minimum subset of 249 TIFF for Facsimile (as specified in [RFC23035]) and a higher quality 250 TIFF using multipart/alternative. 252 Three methods for the sender to acquire such knowledge are 253 described: 255 1. Sender manual configuration 256 2. Capabilities in Directory 257 3. Capabilities returned in MDN or DSN 259 Method (3) SHOULD be used. 261 An implementation may cache capabilities locally and lose 262 synchronization with the recipient's actual capabilities. A 263 mechanism SHOULD be provided to allow the sender to override the 264 locally-stored cache of capabilities. Also note section 4.1 of this 265 document. 267 3.1. Sender Manual Configuration 269 One way a sender can send a document which exceeds the minimum subset 270 allowed by [RFC2305] is for the user controlling the sender to 271 manually override the default settings, usually on a per-recipient 272 basis. For example, during transmission a user could indicate the 273 recipient is capable of receiving high resolution images or color 274 images. 276 While awkward and not automatic, this mechanism reflects the current 277 state of deployment of configuration for extended capabilities to 278 ordinary Internet email users. 280 3.2. Capabilities in Directory 282 A future direction for enhanced document features is to create a 283 directory structure of recipient capabilities, deployed, for example, 284 through LDAP or DNS. The directory would provide a mechanism by which 285 a sender could determine a recipient's capabilities before message 286 construction or transmission, using a directory lookup. Such 287 mechanisms are not defined in this document. 289 There is active investigation within the IETF to develop a solution 290 to this problem, which would resolve a wide range of issues with 291 store-and-forward messaging. 293 3.3. Capabilities Returned in MDN or DSN 295 As outlined in section 2 of this document, a sender may request a 296 positive DSN or an MDN. 298 If the recipient implements [REPORT-EXTENSIONS], the DSN or MDN that 299 is returned can contain information describing the recipient's 300 capabilities. The sender can use this information for subsequent 301 communications with that recipient. 303 The advantage of this approach is that additional infrastructure is 304 not required (unlike section 3.2), and the information is acquired 305 automatically (unlike section 3.1). 307 3.3.1. Restrictions and Recommendations 309 A sender MUST NOT send a message with no processable content to 310 attempt to elicit an MDN/DSN capability response. Doing so with a 311 message with no processable content (such as a message containing 312 only a request for capabilities or a blank message) will confuse a 313 recipient not already designed to understand the semantics of such a 314 message. 316 A recipient SHOULD indicate the profiles and features supported, 317 even if the recipient supports only Tiff Profile S (the minimum 318 set for fax as defined by [RFC2305]) [FAX-SCHEMA]. This allows 319 a sender to determine that the recipient is compliant with 320 this Extended Facsimile Using Internet Mail specification. 322 4. Security Considerations 324 As this document is an extension of [RFC2305], the Security 325 Considerations section of [RFC2305] applies to this document. 327 The following additional security considerations are introduced by 328 the new features described in this document. 330 4.1. Inaccurate Capabilities Information 332 Inaccurate capability information (section 3) could cause a denial of 333 service. The capability information could be inaccurate due to many 334 reasons, including compromised or improperly configured directory 335 server, improper manual configuration of sender, compromised DNS, or 336 spoofed MDN. If a sender is using cached capability information, 337 there SHOULD be a mechanism to allow the cached information to be 338 ignored or overridden if necessary. 340 4.2. Forged MDNs or DSNs 342 Forged DSNs or MDNs, as described in [RFC1892, RFC1894, RFC2298] 343 can provide incorrect information to a sender. 345 5. Implementation Notes 347 This section contains notes to implementors. 349 5.1. Submit Mailer Does Not Support DSN 351 In some installations the generally available submit server may not 352 support DSNs. In such circumstances, it may be useful for the sender 353 to implement [RFC974] mail routing as well as additional submission 354 server functions [SUBMIT] so that the installation is not constrained 355 by limitations of the incumbent submission server. 357 5.2. Recipient Recommendations 359 To provide a high degree of reliability, it is desirable for 360 the sender to know that a recipient could not process a message. 361 The inability to successfully process a message may be detectable 362 by the recipient's MTA or MUA. 364 If the recipient's MTA determines the message cannot be processed, 365 the recipient's MTA is strongly encouraged to reject the message with 366 a [RFC1893] status code of 5.6.1. This status code may be returned 367 in response to the end-of-mail-data indicator if the MTA supports 368 reporting of enhanced error codes [RFC2034], or after message 369 reception by generating a delivery failure DSN ("bounce"). 371 Note: Providing this functionality in the MTA, via either of the 372 two mechanisms described above, is superior to providing the 373 function using MDNs because MDNs must generally be requested 374 by the sender (and the request may, at any time, be ignored by 375 the receiver). Message rejection performed by the MTA can 376 always occur without the sender requesting such behavior and 377 without the receiver circumventing the behavior. 379 If the message contains an MDN request and the recipient's MUA 380 determines the message cannot be processed, the recipient's MUA is 381 strongly encouraged to repond to an MDN request and indicate that 382 processing failed with the disposition-type "processed" or 383 "displayed" and disposition-modifier "error" or "warning" [RFC2298]. 385 6. Acknowledgements 386 The authors would like to acknowledge the members of the IETF 387 Internet Fax working group, and especially the following contributors 388 who provided assistance and input during the development of this 389 document: Vivian Cancio, Richard Coles, David Crocker, Ned Freed, 390 Graham Klyne, MAEDA Toru, Geoff Marshall, Lloyd McIntyre, Keith 391 Moore, George Pajari, James Rafferty, Mike Ruhl, Richard Shockey, 392 Brian Stafford, and Greg Vaudreuil. 394 7. References 396 [CONNEG-FEATURE-SYNTAX] G. Klyne, "A syntax for describing media 397 feature sets", Internet Draft, Work in Progress, 398 draft-ietf-conneg-feature-syntax-XX.txt. 400 [FAX-SCHEMA] L. McIntyre, G. Klyne, "Content feature schema for 401 Internet fax", Internet Draft, Work in Progress, 402 draft-ietf-fax-feature-schema-XX.txt. 404 [REPORT-EXTENSIONS] D. Wing, "Offramp Gateway Extensions to DSN and 405 MDN", Internet Draft, Work in Progress, 406 draft-ietf-fax-reporting-extensions-XX.txt. 408 [RFC1891] K. Moore, "SMTP Service Extensions for Delivery Status 409 Notifications", RFC 1891, January 1996. 411 [RFC1893] G. Vaudreuil, "Enhanced Mail System Status Codes", 412 RFC 1893, January 1996. 414 [RFC1894] K. Moore, G. Vaudreuil, "An Extensible Message Format for 415 Delivery Status Notifications", RFC 1894, January 1996. 417 [RFC2034] N. Freed, "SMTP Service Extension for Returning Enhanced 418 Error Codes", RFC 2034, October 1996. 420 [RFC2119] S. Bradner, "Key words for use in RFCs to Indicate 421 Requirement Levels", RFC 2119, March 1997. 423 [RFC2298] R. Fajman, "An Extensible Message Format for Message 424 Disposition Notifications", RFC 2298, March 1998. 426 [RFC2301] L. McIntyre, S. Zilles, R. Buckley, D. Venable, G. Parsons, 427 J. Rafferty, "File Format for Internet Fax", RFC 2301, March 1998. 429 [RFC2305] K. Toyoda, H. Ohno, J. Murai, D. Wing, "A Simple Mode of 430 Facsimile Using Internet Mail", RFC 2305, March 1998. 432 [RFC974] C. Partridge. "Mail routing and the domain system", RFC 974, 433 January 1986. 435 [SUBMIT] R. Gellens, J. Klensin, "Message Submission", Internet 436 Draft, Work in Progress, draft-gellens-submit-XX.txt. 438 8. Authors' Addresses 440 Larry Masinter 441 Xerox Palo Alto Research Center 442 3333 Coyote Hill Road 443 Palo Alto, CA 94304 USA 445 Fax: +1 650 812 4333 446 EMail: masinter@parc.xerox.com 448 Dan Wing 449 Cisco Systems, Inc. 450 101 Cooper Street 451 Santa Cruz, CA 95060 USA 453 Phone: +1 831 457 5200 454 Fax: +1 831 457 5208 455 EMail: dwing@cisco.com 457 9. Copyright 459 Copyright (C) The Internet Society 1999. All Rights Reserved. 461 This document and translations of it may be copied and furnished to 462 others, and derivative works that comment on or otherwise explain it 463 or assist in its implementation may be prepared, copied, published 464 and distributed, in whole or in part, without restriction of any 465 kind, provided that the above copyright notice and this paragraph are 466 included on all such copies and derivative works. However, this 467 document itself may not be modified in any way, such as by removing 468 the copyright notice or references to the Internet Society or other 469 Internet organizations, except as needed for the purpose of 470 developing Internet standards in which case the procedures for 471 copyrights defined in the Internet Standards process must be 472 followed, or as required to translate it into languages other than 473 English. 475 The limited permissions granted above are perpetual and will not be 476 revoked by the Internet Society or its successors or assigns. 478 This document and the information contained herein is provided on an 479 "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING 480 TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING 481 BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION 482 HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF 483 MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.