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Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Network Working Group E. Wilde 3 Internet-Draft Swiss Federal Institute of 4 Expires: September 30, 2002 Technology 5 A. Vaha-Sipila 6 Nokia 7 April 1, 2002 9 URI scheme for GSM Short Message Service 10 draft-wilde-sms-uri-02 12 Status of this Memo 14 This document is an Internet-Draft and is in full conformance with 15 all provisions of Section 10 of RFC2026. 17 Internet-Drafts are working documents of the Internet Engineering 18 Task Force (IETF), its areas, and its working groups. Note that 19 other groups may also distribute working documents as Internet- 20 Drafts. 22 Internet-Drafts are draft documents valid for a maximum of six months 23 and may be updated, replaced, or obsoleted by other documents at any 24 time. It is inappropriate to use Internet-Drafts as reference 25 material or to cite them other than as "work in progress." 27 The list of current Internet-Drafts can be accessed at http:// 28 www.ietf.org/ietf/1id-abstracts.txt. 30 The list of Internet-Draft Shadow Directories can be accessed at 31 http://www.ietf.org/shadow.html. 33 This Internet-Draft will expire on September 30, 2002. 35 Copyright Notice 37 Copyright (C) The Internet Society (2002). All Rights Reserved. 39 Abstract 41 This memo specifies a URI (Universal Resource Identifier) scheme 42 "sms" for specifying a recipient (and optionally a gateway) for an 43 SMS message. SMS messages are two-way paging messages that can be 44 sent from and received by a mobile phone or a suitably equipped 45 computer. 47 Table of Contents 49 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 50 1.1 The Short Message Service . . . . . . . . . . . . . . . . . 3 51 1.2 Universal Resource Identifiers . . . . . . . . . . . . . . . 3 52 1.3 SMS Messages and the Internet . . . . . . . . . . . . . . . 3 53 1.3.1 SMS Messages and the Web . . . . . . . . . . . . . . . . . . 4 54 1.3.2 SMS Messages and Forms . . . . . . . . . . . . . . . . . . . 4 55 2. The "sms" URI Scheme . . . . . . . . . . . . . . . . . . . . 5 56 2.1 Applicability . . . . . . . . . . . . . . . . . . . . . . . 5 57 2.2 Formal Definition . . . . . . . . . . . . . . . . . . . . . 6 58 2.3 Parsing an "sms" URI . . . . . . . . . . . . . . . . . . . . 6 59 2.4 Examples of Use . . . . . . . . . . . . . . . . . . . . . . 7 60 2.5 Using "sms" URIs in HTML Forms . . . . . . . . . . . . . . . 8 61 3. "sms" URIs and SMS Web Services . . . . . . . . . . . . . . 8 62 3.1 Example . . . . . . . . . . . . . . . . . . . . . . . . . . 9 63 4. Security Considerations . . . . . . . . . . . . . . . . . . 10 64 5. Change Log . . . . . . . . . . . . . . . . . . . . . . . . . 10 65 5.1 From -01 to -02 . . . . . . . . . . . . . . . . . . . . . . 10 66 5.2 From -00 to -01 . . . . . . . . . . . . . . . . . . . . . . 11 67 Normative References . . . . . . . . . . . . . . . . . . . . 11 68 Non-Normative References . . . . . . . . . . . . . . . . . . 12 69 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . 13 70 A. Where to send Comments . . . . . . . . . . . . . . . . . . . 13 71 B. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 13 72 Full Copyright Statement . . . . . . . . . . . . . . . . . . 14 74 1. Introduction 76 Compliant software MUST follow this specification. The capitalized 77 key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 78 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 79 document are to be interpreted as described in RFC 2119 [RFC2119]. 81 1.1 The Short Message Service 83 The Short Message Service (SMS) [SMS] is a rather simple service for 84 sending messages between SMS clients or, using so-called "Telematic 85 Interworking", from an SMS client through a gateway to a receiver 86 using a different service, such as fax or email. The SMS service is 87 described in more detail in the SMS service registration memo [draft- 88 wilde-sms-service-02]. 90 1.2 Universal Resource Identifiers 92 One of the core specifications for identifying resources on the 93 Internet is RFC 2396 [RFC2396], specifying the syntax and semantics 94 of a Universal Resource Identifier (URI). The most important notion 95 of URIs are "schemes", which define a framework within which 96 resources can be identified (and possibly accessed). URIs enable 97 users to identify resources, and are used for very diverse schemes 98 such as access protocols (HTTP, FTP), broadcast media (TV channels 99 [RFC2838]), messaging (email [RFC2368]), or even telephone numbers 100 (voice [RFC2806]). 102 URIs often are mentioned together with Universal Resource Names 103 (URNs) and/or Uniform Resource Locators (URLs), and it often is 104 unclear how to separate these concepts. For the purpose of this 105 memo, only the term URI will be used, referring to the most 106 fundamental concept. The World Wide Web Consortium (W3C) has issued 107 a note [uri-clarification] discussing the topic of URIs, URNs, and 108 URLs in detail. 110 1.3 SMS Messages and the Internet 112 One of the important reasons for the universal access of the Web is 113 the ability to access all information through a unique interface. 114 This kind of integration makes it easy to provide information as well 115 as to consume it. One aspect of this integration is the support of 116 user agents (in the case of the Web, commonly referred to as 117 browsers) for multiple content formats (such as HTML, GIF, JPEG) and 118 access schemes (such as HTTP, HTTP-S, FTP). 120 The "mailto" scheme has proven to be very useful and popular, because 121 most user agents support it by providing an email composition 122 facility when the user activates (eg, clicks on) the URI. 123 Accordingly, the "sms" scheme could be supported by user agents by 124 providing an SMS message composition facility when the user activates 125 the URI. Alternatively, in cases where the user agent does not 126 provide a built-in SMS message composition facility, the scheme could 127 still be supported by opening a Web page which provides such a 128 service. The specific Web page to be used could be configured by the 129 user, so that each user could use the SMS message composition service 130 of his choice. 132 This goal of this memo is to specify the "sms" URI scheme, so that 133 user agents (such as Web browsers and email clients) could start to 134 support it. 136 1.3.1 SMS Messages and the Web 138 SMS messages can provide an alternative to a "mailto" URIs [RFC2368], 139 or "tel" or "fax" URIs [RFC2806]. When a "sms" URI is activated, the 140 user agent MAY start a program for sending an SMS message, just as 141 "mailto" may open a mail client. Unfortunately, most browsers do not 142 support the external handling of internally unsupported URI schemes 143 in the same generalized way as most of them support external handling 144 of additional MIME type content for types which they do not support 145 internally. Ideally, user agents should implement generic URI 146 parsers and provide a way to associate unsupported schemes with 147 external applications (or Web services). 149 The recipient of an SMS message need not be a mobile phone. It can 150 be a server that can process SMS messages, either by gatewaying them 151 to another messaging system (such as regular electronic mail), or by 152 parsing them for supplementary services. 154 SMS messages can be used to transport almost any kind of data (even 155 though there is a very tight size limit), but the only standardized 156 data formats are character-based messages in different character 157 encodings. SMS messages have a maximum length of 160 characters 158 (when using 7-bit characters from the SMS character set), or 140 159 octets. However, SMS messages can be concatenated to form longer 160 messages. It is up to the user agent to decide whether to limit the 161 length of the message, and how to indicate this limit in its user 162 interface, if necessary. There is one exception to this, see Section 163 2.5. 165 1.3.2 SMS Messages and Forms 167 The Hypertext Markup Language (HTML) [HTML401] provides a way to 168 collect information from a user and pass it to a server for 169 processing. This functionality is known as "HTML forms". A filled- 170 in form is usually sent to the destination using the Hypertext 171 Transfer Protocol (HTTP) or email. However, SMS messages can also be 172 used as the transport mechanism for these forms. As SMS transport is 173 "out-of-band" as far as normal HTTP over TCP/IP is concerned, this 174 provides a way to fill in forms offline, and send the data without 175 making a TCP connection to the server, as the set-up time, cost, and 176 overhead for a TCP connection are large compared to an SMS message. 177 Also, depending on the network configuration, the sender's telephone 178 number may be included in the SMS message, thus providing a weak form 179 of authentication. 181 2. The "sms" URI Scheme 183 Syntax definitions are given using the Augmented BNF for Syntax 184 Specifications [RFC2234]. 186 2.1 Applicability 188 This URI scheme is intended for sending an SMS message to a certain 189 recipient(s). The functionality is quite similar to that of the 190 "mailto" URL, which (as per RFC 2368 [RFC2368]) can also be used with 191 a comma-separated list of email addresses. 193 In some situations, it may be necessary to guide the sender to send 194 the SMS message via a certain SMSC. For this purpose, the URI may 195 specify the number of the SMSC. 197 SMS messages may be sent through gateways to other services. These 198 gateways are operated inside SMS centers. An "SMS" URI may specify 199 that a certain gateway should be used. 201 The notation for phone numbers is taken from [draft-allocchio-gstn- 202 03]. Refer to this document for information on why this particular 203 format was chosen. 205 How the SMS message is sent to the SMSC is outside the scope of this 206 specification. SMS messages can be sent over the GSM air interface, 207 by using a modem and a suitable protocol, or by accessing services 208 over other protocols, such as a Web service for sending SMS messages. 209 Also, SMS message service options like deferred delivery and delivery 210 notification requests are not in the scope of this document. Such 211 services MAY be requested from the network by the user agent if 212 necessary. 214 SMS messages sent as a result of this URI MUST be sent as class 1 SMS 215 messages, if the user agent is able to specify the message class. 217 2.2 Formal Definition 219 The URI is case-insensitive. The syntax of an "sms" URI is formally 220 described as follows, where the base syntax is taken from RFC 2396 221 [RFC2396]: 223 sms-uri = scheme ":" scheme-specific-part 224 scheme = "sms" 225 scheme-specific-part = 1*( sms-recipient ) [ sms-body ] 226 sms-recipient = gstn-phone sms-qualifier 227 [ "," sms-recipient ] 228 sms-qualifier = *( smsc-qualifier / pid-qualifier ) 229 smsc-qualifier = ";smsc=" SMSC-sub-addr 230 pid-qualifier = ";pid=" PID-sub-addr 231 sms-body = ";body=" *urlc 233 The syntax definition for "gstn-phone" is taken from [draft- 234 allocchio-gstn-03], allowing global as well as local telephone 235 numbers. 237 The syntax definition for "SMSC-sub-addr" and "PID-sub-addr" is 238 derived from [draft-wilde-sms-service-02], please refer to that 239 document for the syntax of the qualifier values. 241 The "sms-body" is used to define the body of the SMS message to be 242 composed. It consists of URL-encoded UTF-8 characters. 243 Implementations MUST make sure that the sms-body characters are 244 converted to a suitable character encoding before sending, the most 245 popular being the 7-bit SMS character encoding, another variant 246 (though not as universally supported as 7-bit SMS) is the UCS-2 247 character encoding (both specified in [SMS-CHAR]). Implementations 248 MAY choose to silently discard (or convert) characters in the sms- 249 body that are not supported by the SMS character set they are using 250 to send the SMS message. 252 It should be noted that both the SMSC as well as the PID qualifier 253 may appear only once per sms-recipient. If multiple qualifiers are 254 present, conforming software MUST interpret the first occurrence and 255 ignore all other occurrences. 257 2.3 Parsing an "sms" URI 259 The following list describes the steps for processing an "sms" URI: 261 1. The "gstn-phone" of the first "sms-recipient" is extracted. It 262 is the phone number of the final recipient and it MUST be written 263 in international form with country code, unless the number only 264 works from inside a certain geographical area or a network. Note 265 that some numbers may work from several networks but not from the 266 whole world - these SHOULD be written in international form. 267 According to [draft-allocchio-gstn-03], all international numbers 268 MUST begin with a "+" character. Hyphens and dots are only to 269 aid readability. They MUST NOT have any other meaning. 271 2. The "smsc-qualifier" of the first "sms-recipient" is extracted, 272 if present. 274 3. The "pid-qualifier" of the first "sms-recipient" is extracted, if 275 present. 277 4. The "sms-body" is extracted, if present. 279 5. The user agent should provide some means for message composition, 280 either by implementing this itself, or by accessing a service 281 providing it. Message composition SHOULD start with the body 282 extracted from the "sms-body", if present. If the "pid- 283 qualifier" is set to "pid=SMTP:...", then the user agents must 284 make sure that the email address is correctly set (as defined by 285 the SMS specification [SMS]) in the message being composed. 287 6. After message composition, a user agent SHOULD try to send the 288 message first using the SMSC set in the "smsc-qualifier" (if 289 present). If that fails, the user agent MAY try another SMSC. 291 7. If the URI consists of a comma-separated list of recipients (ie, 292 contains multiple "sms-recipient" parts), all of them are 293 processed in this manner. Exactly the same message SHOULD be 294 sent to all of the listed recipients. 296 2.4 Examples of Use 298 sms:+41796431851 300 This indicates an SMS message capable recipient at the given 301 telephone number. The message is sent using the user agent's default 302 SMSC. 304 sms:+41796431851;via=+41794999000 306 This indicates that the SMS message should be sent using the SMSC at 307 the given number. 309 sms:+41796431851,+4116321035;pid=fax 310 This URI should result in two SMS messages being sent, one to the 311 recipient number as shown in the example above, the other one being 312 sent as a fax to the second number (the fax is sent by the SMSC 313 performing the gatewaying, not by the user agent). 315 sms:+41796431851;pid=smtp:ietf@dret.net;body=hello%20there 317 In this case, a message (initially being set to "hello there", which 318 may have been modified by the user before sending) will be sent via 319 SMS using the SMS to email functionality in the SMSC, so that it will 320 eventually result in an email being sent to the specified email 321 address. In this case, the phone number will not be interpreted. 323 2.5 Using "sms" URIs in HTML Forms 325 When using a "sms" type URI as an action URI for HTML form submission 326 [HTML401], the form contents MUST be packaged in the SMS message just 327 as they are packaged when using a "mailto" URL [RFC2368], using the 328 "application/x-www-form-urlencoded" MIME type, effectively packaging 329 all form data into URI compliant syntax [RFC2396]. The SMS message 330 MUST NOT contain any HTTP headers, only the form data. The MIME type 331 is implicit. It MUST NOT be transferred in the SMS message. 333 The character encoding used for form submissions MUST be UTF-8 334 [RFC2279]. It should be noted, however, that user agents MUST URL- 335 encode form submissions before sending them. 337 The user agent SHOULD inform the user about the possible security 338 hazards involved when submitting the form (it is probably being sent 339 as plain text over an air interface). 341 If the form submission is longer than the maximum SMS message size, 342 the user agent MAY either concatenate SMS messages, if it is able to 343 do so, or it MAY refuse to send the message. The user agent MUST NOT 344 send out partial form submissions. 346 Form submission via an "sms" URI can be combined with Telematic 347 Interworking to result in form submissions being submitted via an SMS 348 message and finally being sent to an email account. In this case, 349 all provisions for using the email "pid-qualifier" and using "sms" 350 URIs with HTML forms must be followed. 352 3. "sms" URIs and SMS Web Services 354 In many cases, user agents will not be able to directly compose and 355 send SMS messages (because this requires that such a service is 356 accessible to the system the user agent is running on). However, it 357 is likely that the user has access to a Web service that provides an 358 SMS service, such as a Web site offering form-based SMS composition. 359 Ideally, the user agent should access this Web service when 360 activating an "sms" URI, thus enabling the user to use the Web 361 service. 363 One problem with this approach is that the Web service should somehow 364 get the "sms" URI, in order interpret it and set the required 365 parameters (such as the receiver's phone number). The easiest way to 366 implement this is for the user agent to add the "sms" URI as query 367 string to the Web service's URI. Consequently, user agents 368 supporting SMS Web services identified by URIs SHOULD append the 369 "sms" URI as query string to the Web services URI when accessing the 370 Web service. Web services providing SMS composition facilities 371 SHOULD expect to receive an "sms" URI as query string and should 372 process it as described by this memo. This method only can be 373 applied for Web service URIs which permit query strings (such as 374 "http" and "https" URIs). For other Web service URIs (such as "ftp" 375 and "mailto"), user agents as well as Web services MUST NOT use the 376 query string. 378 It should be noted that RFC 2396 [RFC2396] defines that within query 379 strings, the characters ";", "/", "?", ":", "@", "&", "=", "+", ",", 380 and "$" are reserved. It is therefore necessary to encode the "sms" 381 URI accordingly before appending it as query string. 383 3.1 Example 385 A document contains this piece of (X)HTML: 387 Send me an SMS! 389 The user agent interpreting this document does not internally support 390 SMS message composition, but has configured to access a Web service 391 for handling "sms" URIs. This Web service has the following URI: 393 http://sms.example.com/sms-form 395 When the user activates the "sms" URI (eg, by clicking on the text 396 "Send me an SMS!"), the user agents acts as if the activated URI had 397 been: 399 http://sms.example.com/sms-form?sms%3A%2B41796431851 401 The Web service is then responsible for parsing the query string and 402 providing an approriate interface, for example by already filling in 403 the recipient address with the number provided in the "sms" URI. 405 4. Security Considerations 407 The "Security Considerations" section of the SMS service registration 408 memo [draft-wilde-sms-service-02] MUST be consulted. 410 A user agent SHOULD NOT send out SMS messages without the knowledge 411 of the user, because of associated risks, which include sending 412 masses of SMS messages to a subscriber without his consent, and the 413 costs involved in sending an SMS message. 415 The user agent SHOULD have some mechanism that the user can use to 416 filter out unwanted destinations for SMS messages. The user agent 417 SHOULD also have some means of restricting the number of SMS messages 418 being sent as the result of activating one "sms" URI. 420 If an "sms" URI contains a pid-qualifier and the user agent supports 421 the qualifier and its value, then the user agent MUST set the SMS 422 message's PID as specified by the qualifier. User agents MAY inform 423 users about the value and the functional consequences of PID 424 qualifiers (eg, by notifying users that sending the SMS effectively 425 will result in a fax message being delivered, rather than an SMS 426 message). 428 The method described in section Section 3 adds another level of 429 indirection to the handling of "sms" URIs. If this method is 430 combined with the pid-qualifier gateway functionality, SMS 431 composition and reception will probably be distributed over three 432 different protocols (the Web service, SMS transport itself, and the 433 service selected by the pid-qualifier). User agent SHOULD make this 434 clear to users (either when the Web service is being configured, or 435 when it is accessed). 437 The Telematic Interworking functionality of the SMSC addressed by the 438 pid-qualifier is not necessarily implemented by the SMSC being used, 439 and SMSC providers are known for not or not correctly supporting some 440 or all pid-qualifier values. User agents SHOULD take into account 441 that the success rate of SMS messages being sent using pid-qualifiers 442 is lower than that of "plain" SMS messages. 444 5. Change Log 446 5.1 From -01 to -02 448 o Changed the sms-body field to URL encoded UTF-8 characters. 450 5.2 From -00 to -01 452 o Added the "sms-body" field and its processing rules. 454 o Added Section Section 3 about using "sms" URIs as query strings 455 for SMS Web services. 457 o Fixed typo in ABNF (said "global-phone" instead of "gstn-phone"). 459 o Added some explanatory text about form submissions using email 460 Telematic Interworking. 462 o Added some text about character encoding in form submissions. 464 Normative References 466 [HTML401] Raggett, D., Le Hors, A. and I. Jacobs, 467 "HTML 4.01 Specification", W3C REC- 468 html401, December 1999, . 471 [RFC2119] Bradner, S., "Key words for use in RFCs 472 to Indicate Requirement Levels", RFC 473 2119, March 1997. 475 [RFC2234] Crocker, D. and P. Overell, "Augmented 476 BNF for Syntax Specifications: ABNF", 477 RFC 2234, November 1997. 479 [RFC2279] Yergeau, F., "UTF-8, a transformation 480 format of ISO 10646", RFC 2279, January 481 1998. 483 [RFC2396] Berners-Lee, T., Fielding, R. and L. 484 Masinter, "Uniform Resource Identifiers 485 (URI): Generic Syntax", RFC 2396, 486 August 1998. 488 [SMS] European Telecommunications Standards 489 Institute, "Digital Cellular 490 Telecommunications System (Phase 2+); 491 Technical realization of the Short 492 Message Service (SMS); Point-to-Point 493 (PP)", December 1998, . 496 [SMS-CHAR] European Telecommunications Standards 497 Institute, "ETSI TS 100 901 (GSM 03.38 498 version 7.2.0 Release 1998): Digital 499 Cellular Telecommunications System 500 (Phase 2+); Alphabets and language- 501 specific information", July 1999, 502 . 505 [draft-allocchio-gstn-03] Allocchio, C., "Text string notation 506 for Dial Sequences and GSTN / E.164 507 addresses", draft-allocchio-gstn-03 508 (work in progress), March 2002. 510 [draft-wilde-sms-service-02] Wilde, E., "Registration of GSTN SMS 511 Service Qualifier", draft-wilde-sms- 512 service-02 (work in progress), January 513 2002. 515 Non-Normative References 517 [RFC2368] Hoffmann, P., Masinter, L. and J. Zawinski, "The 518 mailto URL scheme", RFC 2368, June 1998. 520 [RFC2629] Rose, M., "Writing I-Ds and RFCs using XML", RFC 521 2629, June 1999. 523 [RFC2806] Vaha-Sipila, A., "URLs for Telephone Calls", RFC 524 2806, April 2000. 526 [RFC2838] Zigmond, D. and M. Vickers, "Uniform Resource 527 Identifiers for Television Broadcasts", RFC 528 2838, May 2000. 530 [uri-clarification] World Wide Web Consortium, "URIs, URLs, and 531 URNs: Clarifications and Recommendations 1.0", 532 W3C uri-clarification , September 2001, . 535 Authors' Addresses 537 Erik Wilde 538 Swiss Federal Institute of Technology 539 ETH-Zentrum 540 8092 Zurich 541 Switzerland 543 Phone: +41-1-6325132 544 EMail: ietf@dret.net 545 URI: http://dret.net/netdret/ 547 Antti Vaha-Sipila 548 Nokia 550 EMail: antti.vaha-sipila@nokia.com 552 Appendix A. Where to send Comments 554 Please send all comments about this document to Erik Wilde. 556 Appendix B. Acknowledgements 558 This document has been written using the IETF document DTD described 559 in RFC 2629 [RFC2629]. 561 Thanks to Claudio Allocchio for his comments. 563 Full Copyright Statement 565 Copyright (C) The Internet Society (2002). All Rights Reserved. 567 This document and translations of it may be copied and furnished to 568 others, and derivative works that comment on or otherwise explain it 569 or assist in its implementation may be prepared, copied, published 570 and distributed, in whole or in part, without restriction of any 571 kind, provided that the above copyright notice and this paragraph are 572 included on all such copies and derivative works. However, this 573 document itself may not be modified in any way, such as by removing 574 the copyright notice or references to the Internet Society or other 575 Internet organizations, except as needed for the purpose of 576 developing Internet standards in which case the procedures for 577 copyrights defined in the Internet Standards process must be 578 followed, or as required to translate it into languages other than 579 English. 581 The limited permissions granted above are perpetual and will not be 582 revoked by the Internet Society or its successors or assigns. 584 This document and the information contained herein is provided on an 585 "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING 586 TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING 587 BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION 588 HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF 589 MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. 591 Acknowledgement 593 Funding for the RFC Editor function is currently provided by the 594 Internet Society.