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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 November 9, 1998 Dan Wing 5 Expires April 1999 Cisco Systems 6 draft-ietf-fax-eifax-10.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 http://www.imc.org/ietf-fax. 34 Copyright Notice 36 Copyright (C) The Internet Society (1998). 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 NOTE: The authors of this document have recently been made aware of 51 several intellectual property claims that relate to the technology 52 described in this document, including US patents 5812278 and 5805298. 53 This disclosure is being made according to the rules laid out in RFC 54 2026 and 2028, where contributors are required to disclose the 55 existence of any proprietary or intellectual property rights in the 56 contribution that are reasonably and personally known to the 57 contributor. These intellectual property claims may interfere with 58 this specification moving forward along standards track. 60 1. Introduction 62 This document notes a number of enhancements to the "Simple Mode of 63 Facsimile Using Internet Mail" [RFC2305] that may be combined to 64 create an extended mode of facsimile using Internet mail. 66 The new features are designed to be interoperable with the existing 67 base of mail transfer agents (MTAs) and mail user agents (MUAs), 68 and take advantage of existing standards for advanced functionality 69 such as positive delivery confirmation and disposition notification. 70 The enhancements described in this document utilize the messaging 71 infrastructure, where possible, instead of creating fax-specific 72 features which are unlikely to be implemented in non-fax messaging 73 software. 75 This document standardizes two features described in its companion 76 document, [GOALS]: 78 * Delivery confirmation (Section 2) (required) 79 * Additional document features (Section 3) (optional) 81 1.1. Definition of terms 83 The term "processing" indicates the ability to successfully render or 84 transmit the contents of the message to a printer, display device, or 85 fax machine. 87 The term "recipient" indicates the device which performs the 88 processing function. For example, a recipient could be implemented 89 as a traditional Mail User Agent on a PC, a standalone device which 90 retrieves mail using POP3 or IMAP, an SMTP server which prints 91 incoming messages (similar to an LPR server). 93 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 94 "SHOULD", SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 95 document are to be interpreted as described in [RFC2119]. 97 1.2. GSTN Fax Gateways ("onramp"/"offramp") 98 The behavior of gateways from GSTN fax to SMTP ("onramps") and from 99 SMTP to GSTN fax ("offramps") are not described in this document. 100 However, such gateways SHOULD have the behavior characteristics of 101 senders and recipients as described in this document. 103 2. Delivery and Processing Confirmation 105 In traditional GSTN-based realtime facsimile, the receiving terminal 106 acknowledges successful receipt and processing of every page [T.30]. 108 In Internet Mail, the operations of Delivery (to the mailbox) and 109 Disposition (to paper or a screen) may be separated in time (due to 110 store and forwarding of messages) and location (due to separation of 111 delivery agent (MTA) and user agent (MUA)). The confirmation of 112 these two operations are supplied by two different standards-track 113 mechanisms: Delivery Status Notifications (DSN) [RFC1891, RFC1894] 114 and Message Disposition Notifications (MDN) [RFC2298], respectively. 116 This section defines requirements for devices or services that are to 117 be considered compliant with this document. 119 2.1. Sender Requirements 121 A delivery failure message (in the format described by [RFC1894] or 122 otherwise) may be sent to the envelope-from address specified by the 123 sender. Thus, the envelope-from address supplied by the sender MUST 124 be able to properly handle such delivery failure messages. 126 2.1.1. Delivery Confirmation 128 If the sender desires delivery confirmation, the sender MUST request 129 Delivery Status Notification by including the the esmtp-keyword 130 NOTIFY with the esmtp-value SUCCESS [section 5.1 of RFC1891]. 132 2.1.2. Processing Confirmation 134 If the sender desires processing confirmation, the sender MUST 135 request Message Disposition Notification [RFC2298 section 2] 136 when sending the message itself. 138 Because a recipient may silently ignore a request for an MDN [section 139 2.1 of RFC2298] at any time: 140 * MDNs MUST NOT be used for delivery confirmation, but are only 141 useful for disposition ("processing") notification. 142 * the sender MUST NOT assume the recipient will respond to an MDN 143 request in a subsequent message, even if the recipient has 144 done so in the past. 146 The address provided by the sender on the Disposition-Notification-To 147 field MUST be able to receive Message Disposition Notifications 148 messages [RFC2298] and SHOULD be able to receive messages that are 149 not in the Message Disposition Notification format (due to the 150 existence of legacy systems that generate non-RFC2298-compliant 151 responses to the Disposition-Notification-To field). 153 2.2. Recipient Requirements 155 Recipients SHOULD implement Message Disposition Notifications 156 [RFC2298] and SHOULD indicate supported media features in 157 DSN and MDN messages per [REPORT-EXTENSIONS]. 159 If the recipient is an SMTP server, it behaves as part of the 160 receiver infrastructure and is therefore subject to the "Receiver 161 Infrastructure" requirements of this document. 163 See also "Recipient Recommendations" in section 5. 165 2.2.1. MDN Recipient Requirements 167 Recipients MUST be configurable to silently ignore a request for an 168 MDN ([section 2.1 of RFC2298]). 170 If the recipient is an automated message processing system which is 171 not associated with a person, the device MAY be configurable to 172 always respond to MDN requests, but in all cases MUST be configurable 173 to never generate MDNs. 175 A recipient MUST NOT generate an unsolicited MDN to indicate 176 successful processing. A recipient MAY generate an unsolicited MDN 177 (sent to the envelope-from (Return-Path:) address) to indicate 178 processing failure, but subject to the [RFC2298] requirement that it 179 MUST always be possible for an operator to disable unsolicited MDN 180 generation. 182 2.2.2. Recipients using Mailbox Access Protocols 184 A recipient using [POP3] or [IMAP4] to retrieve its mail MUST NOT 185 generate a Delivery Status Notification message [RFC1894]. 187 The recipient MUST NOT use the RFC822 "To:" fields, "Cc:" fields, 188 "Bcc:" fields, or any other fields containing header recipient 189 information to determine the ultimate destination mailbox or 190 addressee, and SHOULD NOT use other RFC822 or MIME fields for making 191 such determinations. 193 2.3. Messaging Infrastructure Requirements 194 This section explains the requirements of the SMTP messaging 195 infrastructure used by the sender and receiver. This infrastructure 196 is commonly provided by the ISP or a company's internal mailers but 197 can actually be provided by another organization with appropriate 198 service contracts. 200 2.3.1. Sender Infrastructure 202 Support for DSN [RFC1891] MUST be provided by the mail submission 203 server [SUBMIT] used by the sender and MUST be provided up to the 204 mailer responsible for communicating with external (Internet) 205 mailers. 207 Also see section 5.1 of this document. 209 2.3.2. Receiver Infrastructure 211 Support for DSN [RFC1891] MUST be provided by the external 212 (Internet-accessible) mailer, and MUST be provided by each mailer 213 between the external mailer and the recipient. If the recipient is 214 implemented as an SMTP server it MUST also support DSN [RFC1891]. 216 3. Additional document capabilities 218 Section 4 of "A Simple Mode of Facsimile Using Internet Mail" 219 [RFC2305] allows sending only the minimum subset of TIFF for 220 Facsimile "unless the sender has prior knowledge of other TIFF fields 221 or values supported by the recipient." 223 A recipient MAY support any or all (or any combination) of the TIFF 224 profiles defined in RFC 2301, in addition to profile S. A recipient 225 which supports additional profiles SHOULD indicate this support as 226 per section 3.2 or 3.3 of this document. As a consequence, a sender 227 MAY use those additional TIFF profiles when sending to a recipient 228 with the corresponding capabilities. 230 A sender SHOULD be able to recognize and process the feature tags as 231 defined in [FAX-SCHEMA] when reviewing the capabilities presented by 232 a potential recipient. The capability matching rules indicated there 233 (by reference to [CONNEG-FEATURE-SYNTAX]) allow for the introduction 234 of new features that may be unrecognized by older implementations. 236 A sender MAY send a message containing both the minimum subset of 237 TIFF for Facsimile (as specified in [RFC23035]) and a higher quality 238 TIFF using multipart/alternative. 240 Three methods for the sender to acquire such knowledge are 241 described: 243 1. Sender manual configuration 244 2. Capabilities in Directory 245 3. Capabilities returned in MDN or DSN 247 Method (3) SHOULD be used. 249 An implementation may cache capabilities locally and lose 250 synchronization with the recipient's actual capabilities. A 251 mechanism should be provided to allow the sender to override the 252 locally-stored cache of capabilities. Also note section 4.1 of this 253 document. 255 3.1. Sender manual configuration 257 One way a sender can send a document which exceeds the minimum subset 258 allowed by [RFC2305] is for the user controlling the sender to 259 manually override the default settings, usually on a per-recipient 260 basis. For example, during transmission a user could indicate the 261 recipient is capable of receiving high resolution images or color 262 images. 264 While awkward and not automatic, this mechanism reflects the current 265 state of deployment of configuration for extended capabilities to 266 ordinary Internet email users. 268 3.2. Capabilities in Directory 270 A future direction for enhanced document features is to create a 271 directory structure of recipient capabilities, deployed, for example, 272 through LDAP or DNS. The directory would provide a mechanism by which 273 a sender could determine a recipient's capabilities before message 274 construction or transmission, using a directory lookup. Such 275 mechanisms are not defined in this document. 277 There is active investigation within the IETF to develop a solution 278 to this problem, which would resolve a wide range of issues with 279 store-and-forward messaging. 281 3.3. Capabilities Returned in MDN or DSN 283 As outlined in section 2 of this document, a sender may request a 284 positive DSN or an MDN. 286 If the recipient implements [REPORT-EXTENSIONS], the DSN or MDN that 287 is returned can contain information describing the recipient's 288 capabilities. The sender can use this information for subsequent 289 communications with that recipient. 291 The advantage of this approach is that additional infrastructure is 292 not required (unlike section 3.2), and the information is acquired 293 automatically (unlike section 3.1). 295 3.3.1. Restrictions and Recommendations 297 A sender MUST NOT send a message with no processable content to 298 attempt to elicit an MDN/DSN capability response. Doing so with a 299 message with no processable content (such as a message containing 300 only a request for capabilities or a blank message) will confuse a 301 recipient not already designed to understand the semantics of such a 302 message. 304 A recipient SHOULD indicate the profiles and features supported, 305 even if the recipient supports only Tiff Profile S (the minimum 306 set for fax as defined by [RFC2305]) [FAX-SCHEMA]. This allows 307 a sender to determine that the recipient is compliant with 308 this specification. 310 4. Security Considerations 312 As this document is an extension of [RFC2305], the Security 313 Considerations section of [RFC2305] applies to this document. 315 The following additional security considerations are introduced by 316 the new features described in this document. 318 4.1. Inaccurate Capabilities Information 320 Inaccurate capability information (section 3) could cause a denial of 321 service. The capability information could be inaccurate due to many 322 reasons, including compromised or improperly configured directory 323 server, improper manual configuration of sender, compromised DNS, or 324 spoofed MDN. If a sender is using cached capability information, 325 there SHOULD be a mechanism to allow the cached information to be 326 ignored or overridden if necessary. 328 4.2. Forged MDNs or DSNs 330 Forged DSNs or MDNs, as described in [RFC1892, RFC1894, RFC2298] 331 can provide incorrect information to a sender. 333 5. Implementation Notes 335 This section contains notes to implementors. 337 5.1. Submit mailer does not support DSN 338 In some installations the generally available submit server may not 339 support DSNs. In such circumstances, it may be useful for the sender 340 to implement [RFC974] mail routing as well as additional submission 341 server functions [SUBMIT] so that the installation is not constrained 342 by limitations of the incumbent submission server. 344 5.2. Recipient Recommendations 346 To provide a high degree of reliability, it is desirable for 347 the sender to know that a recipient could not process a message. 348 The inability to successfully process a message may be detectable 349 by the recipient's MTA or MUA. 351 If the recipient's MTA determines the message cannot be processed, 352 the recipient's MTA is strongly encouraged to reject the message with 353 a [RFC1893] status code of 5.6.1. This status code may be returned 354 in response to the end-of-mail-data indicator if the MTA supports 355 reporting of enhanced error codes [RFC2034], or after message 356 reception by generating a delivery failure DSN ("bounce"). 358 Note: Providing this functionality in the MTA, via either of the 359 two mechanisms described above, is superior to providing the 360 function using MDNs because MDNs must be requested by the 361 sender (and the request may, at any time, be ignored by 362 the receiver). Message rejection performed by the MTA can 363 always occur without the sender requesting such behavior 364 and without the receiver circumventing the behavior. 366 If the message contains an MDN request and the recipient's MUA 367 determines the message cannot be processed, the recipient's MUA is 368 strongly encouraged to repond to an MDN request and indicate that 369 processing failed with the disposition-type "processed" or 370 "displayed" and disposition-modifier "error" or "warning" [RFC2298]. 372 6. Acknowledgements 374 The authors would like to acknowledge the members of the IETF 375 Internet Fax working group, and especially the following contributors 376 who provided assistance and input during the development of this 377 document: Vivian Cancio, Richard Coles, David Crocker, Ned Freed, 378 Graham Klyne, MAEDA Toru, Geoff Marshall, Lloyd McIntyre, Keith 379 Moore, George Pajari, James Rafferty, Mike Ruhl, Richard Shockey, 380 Brian Stafford, and Greg Vaudreuil. 382 7. References 384 [CONNEG-FEATURE-SYNTAX] G. Klyne, "A syntax for describing media 385 feature sets", Internet Draft, Work in Progress, 386 draft-ietf-conneg-feature-syntax-XX.txt. 388 [FAX-SCHEMA] L. McIntyre, G. Klyne, "Content feature schema for 389 Internet fax", Internet Draft, Work in Progress, 390 draft-ietf-fax-feature-schema-XX.txt. 392 [GOALS] L. Masinter, "Terminology and Goals for Internet Fax", 393 Internet Draft, Work in Progress, draft-ietf-fax-goals-XX.txt, 394 LAST CALL. 396 [REPORT-EXTENSIONS] D. Wing, "Offramp Gateway Extensions to DSN and 397 MDN", Internet Draft, Work in Progress, 398 draft-ietf-fax-reporting-extensions-XX.txt. 400 [RFC1891] K. Moore, "SMTP Service Extensions for Delivery Status 401 Notifications", RFC 1891, January 1996. 403 [RFC1893bis] G. Vaudreuil, "Enhanced Mail System Status Codes", 404 Internet Draft, Work in Progress, (update to RFC 1893). 406 [RFC1894] K. Moore, G. Vaudreuil, "An Extensible Message Format for 407 Delivery Status Notifications", RFC 1894, January 1996. 409 [RFC2034] N. Freed, "SMTP Service Extension for Returning Enhanced 410 Error Codes", RFC 2034, October 1996. 412 [RFC2119] S. Bradner, "Key words for use in RFCs to Indicate 413 Requirement Levels", RFC 2119, March 1997. 415 [RFC2298] R. Fajman, "An Extensible Message Format for Message 416 Disposition Notifications", RFC 2298, March 1998. 418 [RFC2301] L. McIntyre, S. Zilles, R. Buckley, D. Venable, G. Parsons, 419 J. Rafferty, "File Format for Internet Fax", RFC 2301, March 1998. 421 [RFC2305] K. Toyoda, H. Ohno, J. Murai, D. Wing, "A Simple Mode of 422 Facsimile Using Internet Mail", RFC 2305, March 1998. 424 [RFC974] C. Partridge. "Mail routing and the domain system", RFC 974, 425 January 1986. 427 [SUBMIT] R. Gellens, J. Klensin, "Message Submission", Internet 428 Draft, Work in Progress, draft-gellens-submit-XX.txt. 430 8. Authors' Addresses 432 Larry Masinter 433 Xerox Palo Alto Research Center 434 3333 Coyote Hill Road 435 Palo Alto, CA 94304 USA 437 Fax: +1 415 812 4333 438 EMail: masinter@parc.xerox.com 440 Dan Wing 441 Cisco Systems, Inc. 442 101 Cooper Street 443 Santa Cruz, CA 95060 USA 445 Phone: +1 831 457 5200 446 Fax: +1 831 457 5208 447 EMail: dwing@cisco.com 449 9. Copyright 451 Copyright (C) The Internet Society 1998. All Rights Reserved. 453 This document and translations of it may be copied and furnished to 454 others, and derivative works that comment on or otherwise explain it 455 or assist in its implementation may be prepared, copied, published 456 and distributed, in whole or in part, without restriction of any 457 kind, provided that the above copyright notice and this paragraph are 458 included on all such copies and derivative works. However, this 459 document itself may not be modified in any way, such as by removing 460 the copyright notice or references to the Internet Society or other 461 Internet organizations, except as needed for the purpose of 462 developing Internet standards in which case the procedures for 463 copyrights defined in the Internet Standards process must be 464 followed, or as required to translate it into languages other than 465 English. 467 The limited permissions granted above are perpetual and will not be 468 revoked by the Internet Society or its successors or assigns. 470 This document and the information contained herein is provided on an 471 "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING 472 TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING 473 BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION 474 HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF 475 MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.