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2 Network Working Group E. Wilde
3 Internet-Draft Swiss Federal Institute of
4 Expires: July 25, 2002 Technology
5 A. Vaha-Sipila
6 Nokia
7 January 24, 2002
9 URI scheme for GSM Short Message Service
10 draft-wilde-sms-uri-01
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 July 25, 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 . . . . . . . . . . . . . . . . . . 9
64 5. Change Log . . . . . . . . . . . . . . . . . . . . . . . . . 10
65 5.1 From -00 to -01 . . . . . . . . . . . . . . . . . . . . . . 10
66 Normative References . . . . . . . . . . . . . . . . . . . . 11
67 Non-Normative References . . . . . . . . . . . . . . . . . . 12
68 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . 12
69 A. Where to send Comments . . . . . . . . . . . . . . . . . . . 12
70 B. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 12
71 Full Copyright Statement . . . . . . . . . . . . . . . . . . 14
73 1. Introduction
75 Compliant software MUST follow this specification. The capitalized
76 key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
77 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
78 document are to be interpreted as described in RFC 2119 [RFC2119].
80 1.1 The Short Message Service
82 The Short Message Service (SMS) [SMS] is a rather simple service for
83 sending messages between SMS clients or, using so-called "Telematic
84 Interworking", from an SMS client through a gateway to a receiver
85 using a different service, such as fax or email. The SMS service is
86 described in more detail in the SMS service registration memo [draft-
87 wilde-sms-service-01].
89 1.2 Universal Resource Identifiers
91 One of the core specifications for identifying resources on the
92 Internet is RFC 2396 [RFC2396], specifying the syntax and semantics
93 of a Universal Resource Identifier (URI). The most important notion
94 of URIs are "schemes", which define a framework within which
95 resources can be identified (and possibly accessed). URIs enable
96 users to identify resources, and are used for very diverse schemes
97 such as access protocols (HTTP, FTP), broadcast media (TV channels
98 [RFC2838]), messaging (email [RFC2368]), or even telephone numbers
99 (voice [RFC2806]).
101 URIs often are mentioned together with Universal Resource Names
102 (URNs) and/or Uniform Resource Locators (URLs), and it often is
103 unclear how to separate these concepts. For the purpose of this
104 memo, only the term URI will be used, referring to the most
105 fundamental concept. The World Wide Web Consortium (W3C) has issued
106 a note [uri-clarification] discussing the topic of URIs, URNs, and
107 URLs in detail.
109 1.3 SMS Messages and the Internet
111 One of the important reasons for the universal access of the Web is
112 the ability to access all information through a unique interface.
113 This kind of integration makes it easy to provide information as well
114 as to consume it. One aspect of this integration is the support of
115 user agents (in the case of the Web, commonly referred to as
116 browsers) for multiple content formats (such as HTML, GIF, JPEG) and
117 access schemes (such as HTTP, HTTP-S, FTP).
119 The "mailto" scheme has proven to be very useful and popular, because
120 most user agents support it by providing an email composition
121 facility when the user activates (eg, clicks on) the URI.
122 Accordingly, the "sms" scheme could be supported by user agents by
123 providing an SMS message composition facility when the user activates
124 the URI. Alternatively, in cases where the user agent does not
125 provide a built-in SMS message composition facility, the scheme could
126 still be supported by opening a Web page which provides such a
127 service. The specific Web page to be used could be configured by the
128 user, so that each user could use the SMS message composition service
129 of his choice.
131 This goal of this memo is to specify the "sms" URI scheme, so that
132 user agents (such as Web browsers and email clients) could start to
133 support it.
135 1.3.1 SMS Messages and the Web
137 SMS messages can provide an alternative to a "mailto" URIs [RFC2368],
138 or "tel" or "fax" URIs [RFC2806]. When a "sms" URI is activated, the
139 user agent MAY start a program for sending an SMS message, just as
140 "mailto" may open a mail client. Unfortunately, most browsers do not
141 support the external handling of internally unsupported URI schemes
142 in the same generalized way as most of them support external handling
143 of additional MIME type content for types which they do not support
144 internally. Ideally, user agents should implement generic URI
145 parsers and provide a way to associate unsupported schemes with
146 external applications (or Web services).
148 The recipient of an SMS message need not be a mobile phone. It can
149 be a server that can process SMS messages, either by gatewaying them
150 to another messaging system (such as regular electronic mail), or by
151 parsing them for supplementary services.
153 SMS messages can be used to transport almost any kind of data (even
154 though there is a very tight size limit), but the only standardized
155 data formats are character-based messages in different character
156 encodings. SMS messages have a maximum length of 160 characters
157 (when using 7-bit characters from the SMS character set), or 140
158 octets. However, SMS messages can be concatenated to form longer
159 messages. It is up to the user agent to decide whether to limit the
160 length of the message, and how to indicate this limit in its user
161 interface, if necessary. There is one exception to this, see Section
162 2.5.
164 1.3.2 SMS Messages and Forms
166 The Hypertext Markup Language (HTML) [HTML401] provides a way to
167 collect information from a user and pass it to a server for
168 processing. This functionality is known as "HTML forms". A filled-
169 in form is usually sent to the destination using the Hypertext
170 Transfer Protocol (HTTP) or email. However, SMS messages can also be
171 used as the transport mechanism for these forms. As SMS transport is
172 "out-of-band" as far as normal HTTP over TCP/IP is concerned, this
173 provides a way to fill in forms offline, and send the data without
174 making a TCP connection to the server, as the set-up time, cost, and
175 overhead for a TCP connection are large compared to an SMS message.
176 Also, depending on the network configuration, the sender's telephone
177 number may be included in the SMS message, thus providing a weak form
178 of authentication.
180 2. The "sms" URI Scheme
182 Syntax definitions are given using the Augmented BNF for Syntax
183 Specifications [RFC2234].
185 2.1 Applicability
187 This URI scheme is intended for sending an SMS message to a certain
188 recipient(s). The functionality is quite similar to that of the
189 "mailto" URL, which (as per RFC 2368 [RFC2368]) can also be used with
190 a comma-separated list of email addresses.
192 In some situations, it may be necessary to guide the sender to send
193 the SMS message via a certain SMSC. For this purpose, the URI may
194 specify the number of the SMSC.
196 SMS messages may be sent through gateways to other services. These
197 gateways are operated inside SMS centers. An "SMS" URI may specify
198 that a certain gateway should be used.
200 The notation for phone numbers is taken from [draft-allocchio-gstn-
201 01]. Refer to this document for information on why this particular
202 format was chosen.
204 How the SMS message is sent to the SMSC is outside the scope of this
205 specification. SMS messages can be sent over the GSM air interface,
206 by using a modem and a suitable protocol, or by accessing services
207 over other protocols, such as a Web service for sending SMS messages.
208 Also, SMS message service options like deferred delivery and delivery
209 notification requests are not in the scope of this document. Such
210 services MAY be requested from the network by the user agent if
211 necessary.
213 SMS messages sent as a result of this URI MUST be sent as class 1 SMS
214 messages, if the user agent is able to specify the message class.
216 2.2 Formal Definition
218 The URI is case-insensitive. The syntax of an "sms" URI is formally
219 described as follows, where the base syntax is taken from RFC 2396
220 [RFC2396]:
222 sms-uri = scheme ":" scheme-specific-part
223 scheme = "sms"
224 scheme-specific-part = 1*( sms-recipient ) [ sms-body ]
225 sms-recipient = gstn-phone sms-qualifier
226 [ "," sms-recipient ]
227 sms-qualifier = *( smsc-qualifier / pid-qualifier )
228 smsc-qualifier = ";smsc=" SMSC-sub-addr
229 pid-qualifier = ";pid=" PID-sub-addr
230 sms-body = ";body=" *urlc
232 The syntax definition for "gstn-phone" is taken from [draft-
233 allocchio-gstn-01], allowing global as well as local telephone
234 numbers.
236 The syntax definition for "SMSC-sub-addr" and "PID-sub-addr" is
237 derived from [draft-wilde-sms-service-01], please refer to that
238 document for the syntax of the qualifier values.
240 The "sms-body" is used to define the body of the SMS message to be
241 composed. It consists or URL-encoded characters. Only characters
242 from the 7-bit SMS character set [SMS-CHAR] are allowed.
244 It should be noted that both the SMSC as well as the PID qualifier
245 may appear only once per sms-recipient. If multiple qualifiers are
246 present, conforming software MUST interpret the first occurrence and
247 ignore all other occurrences.
249 2.3 Parsing an "sms" URI
251 The following list describes the steps for processing an "sms" URI:
253 1. The "gstn-phone" of the first "sms-recipient" is extracted. It
254 is the phone number of the final recipient and it MUST be written
255 in international form with country code, unless the number only
256 works from inside a certain geographical area or a network. Note
257 that some numbers may work from several networks but not from the
258 whole world - these SHOULD be written in international form.
259 According to [draft-allocchio-gstn-01], all international numbers
260 MUST begin with a "+" character. Hyphens and dots are only to
261 aid readability. They MUST NOT have any other meaning.
263 2. The "smsc-qualifier" of the first "sms-recipient" is extracted,
264 if present.
266 3. The "pid-qualifier" of the first "sms-recipient" is extracted, if
267 present.
269 4. The "sms-body" is extracted, if present.
271 5. The user agent should provide some means for message composition,
272 either by implementing this itself, or by accessing a service
273 providing it. Message composition SHOULD start with the body
274 extracted from the "sms-body", if present. If the "pid-
275 qualifier" is set to "pid=SMTP:...", then the user agents must
276 make sure that the email address is correctly set (as defined by
277 the SMS specification [SMS]) in the message being composed.
279 6. After message composition, a user agent SHOULD try to send the
280 message first using the SMSC set in the "smsc-qualifier" (if
281 present). If that fails, the user agent MAY try another SMSC.
283 7. If the URI consists of a comma-separated list of recipients (ie,
284 contains multiple "sms-recipient" parts), all of them are
285 processed in this manner. Exactly the same message SHOULD be
286 sent to all of the listed recipients.
288 2.4 Examples of Use
290 sms:+41796431851
292 This indicates an SMS message capable recipient at the given
293 telephone number. The message is sent using the user agent's default
294 SMSC.
296 sms:+41796431851;via=+41794999000
298 This indicates that the SMS message should be sent using the SMSC at
299 the given number.
301 sms:+41796431851,+4116321035;pid=fax
303 This URI should result in two SMS messages being sent, one to the
304 recipient number as shown in the example above, the other one being
305 sent as a fax to the second number (the fax is sent by the SMSC
306 performing the gatewaying, not by the user agent).
308 sms:+41796431851;pid=smtp:ietf@dret.net;body=hello%20there
309 In this case, a message (initially being set to "hello there", which
310 may have been modified by the user before sending) will be sent via
311 SMS using the SMS to email functionality in the SMSC, so that it will
312 eventually result in an email being sent to the specified email
313 address. In this case, the phone number will not be interpreted.
315 2.5 Using "sms" URIs in HTML Forms
317 When using a "sms" type URI as an action URI for HTML form submission
318 [HTML401], the form contents MUST be packaged in the SMS message just
319 as they are packaged when using a "mailto" URL [RFC2368], using the
320 "application/x-www-form-urlencoded" MIME type, effectively packaging
321 all form data into URI compliant syntax [RFC2396]. The SMS message
322 MUST NOT contain any HTTP headers, only the form data. The MIME type
323 is implicit. It MUST NOT be transferred in the SMS message.
325 The character encoding used for form submissions MUST be UTF-8
326 [RFC2279]. It should be noted, however, that user agents MUST URL-
327 encode form submissions before sending them.
329 The user agent SHOULD inform the user about the possible security
330 hazards involved when submitting the form (it is probably being sent
331 as plain text over an air interface).
333 If the form submission is longer than the maximum SMS message size,
334 the user agent MAY either concatenate SMS messages, if it is able to
335 do so, or it MAY refuse to send the message. The user agent MUST NOT
336 send out partial form submissions.
338 Form submission via an "sms" URI can be combined with Telematic
339 Interworking to result in form submissions being submitted via an SMS
340 message and finally being sent to an email account. In this case,
341 all provisions for using the email "pid-qualifier" and using "sms"
342 URIs with HTML forms must be followed.
344 3. "sms" URIs and SMS Web Services
346 In many cases, user agents will not be able to directly compose and
347 send SMS messages (because this requires that such a service is
348 accessible to the system the user agent is running on). However, it
349 is likely that the user has access to a Web service that provides an
350 SMS service, such as a Web site offering form-based SMS composition.
351 Ideally, the user agent should access this Web service when
352 activating an "sms" URI, thus enabling the user to use the Web
353 service.
355 One problem with this approach is that the Web service should somehow
356 get the "sms" URI, in order interpret it and set the required
357 parameters (such as the receiver's phone number). The easiest way to
358 implement this is for the user agent to add the "sms" URI as query
359 string to the Web service's URI. Consequently, user agents
360 supporting SMS Web services identified by URIs SHOULD append the
361 "sms" URI as query string to the Web services URI when accessing the
362 Web service. Web services providing SMS composition facilities
363 SHOULD expect to receive an "sms" URI as query string and should
364 process it as described by this memo. This method only can be
365 applied for Web service URIs which permit query strings (such as
366 "http" and "https" URIs). For other Web service URIs (such as "ftp"
367 and "mailto"), user agents as well as Web services MUST NOT use the
368 query string.
370 It should be noted that RFC 2396 [RFC2396] defines that within query
371 strings, the characters ";", "/", "?", ":", "@", "&", "=", "+", ",",
372 and "$" are reserved. It is therefore necessary to encode the "sms"
373 URI accordingly before appending it as query string.
375 3.1 Example
377 A document contains this piece of (X)HTML:
379 Send me an SMS!
381 The user agent interpreting this document does not internally support
382 SMS message composition, but has configured to access a Web service
383 for handling "sms" URIs. This Web service has the following URI:
385 http://sms.example.com/sms-form
387 When the user activates the "sms" URI (eg, by clicking on the text
388 "Send me an SMS!"), the user agents acts as if the activated URI had
389 been:
391 http://sms.example.com/sms-form?sms%3A%2B41796431851
393 The Web service is then responsible for parsing the query string and
394 providing an approriate interface, for example by already filling in
395 the recipient address with the number provided in the "sms" URI.
397 4. Security Considerations
399 The "Security Considerations" section of the SMS service registration
400 memo [draft-wilde-sms-service-01] MUST be consulted.
402 A user agent SHOULD NOT send out SMS messages without the knowledge
403 of the user, because of associated risks, which include sending
404 masses of SMS messages to a subscriber without his consent, and the
405 costs involved in sending an SMS message.
407 The user agent SHOULD have some mechanism that the user can use to
408 filter out unwanted destinations for SMS messages. The user agent
409 SHOULD also have some means of restricting the number of SMS messages
410 being sent as the result of activating one "sms" URI.
412 If an "sms" URI contains a pid-qualifier and the user agent supports
413 the qualifier and its value, then the user agent MUST set the SMS
414 message's PID as specified by the qualifier. User agents MAY inform
415 users about the value and the functional consequences of PID
416 qualifiers (eg, by notifying users that sending the SMS effectively
417 will result in a fax message being delivered, rather than an SMS
418 message).
420 The method described in section Section 3 adds another level of
421 indirection to the handling of "sms" URIs. If this method is
422 combined with the pid-qualifier gateway functionality, SMS
423 composition and reception will probably be distributed over three
424 different protocols (the Web service, SMS transport itself, and the
425 service selected by the pid-qualifier). User agent SHOULD make this
426 clear to users (either when the Web service is being configured, or
427 when it is accessed).
429 The Telematic Interworking functionality of the SMSC addressed by the
430 pid-qualifier is not necessarily implemented by the SMSC being used,
431 and SMSC providers are known for not or not correctly supporting some
432 or all pid-qualifier values. User agents SHOULD take into account
433 that the success rate of SMS messages being sent using pid-qualifiers
434 is lower than that of "plain" SMS messages.
436 5. Change Log
438 5.1 From -00 to -01
440 o Added the "sms-body" field and its processing rules.
442 o Added Section Section 3 about using "sms" URIs as query strings
443 for SMS Web services.
445 o Fixed typo in ABNF (said "global-phone" instead of "gstn-phone").
447 o Added some explanatory text about form submissions using email
448 Telematic Interworking.
450 o Added some text about character encoding in form submissions.
452 Normative References
454 [HTML401] Raggett, D., Le Hors, A. and I. Jacobs,
455 "HTML 4.01 Specification", W3C REC-
456 html401, December 1999, .
459 [RFC2119] Bradner, S., "Key words for use in RFCs
460 to Indicate Requirement Levels", RFC
461 2119, March 1997.
463 [RFC2234] Crocker, D. and P. Overell, "Augmented
464 BNF for Syntax Specifications: ABNF",
465 RFC 2234, November 1997.
467 [RFC2279] Yergeau, F., "UTF-8, a transformation
468 format of ISO 10646", RFC 2279, January
469 1998.
471 [RFC2396] Berners-Lee, T., Fielding, R. and L.
472 Masinter, "Uniform Resource Identifiers
473 (URI): Generic Syntax", RFC 2396,
474 August 1998.
476 [SMS] European Telecommunications Standards
477 Institute, "Digital Cellular
478 Telecommunications System (Phase 2+);
479 Technical realization of the Short
480 Message Service (SMS); Point-to-Point
481 (PP)", December 1998, .
484 [SMS-CHAR] European Telecommunications Standards
485 Institute, "ETSI TS 100 901 (GSM 03.38
486 version 7.2.0 Release 1998): Digital
487 Cellular Telecommunications System
488 (Phase 2+); Alphabets and language-
489 specific information", July 1999,
490 .
493 [draft-allocchio-gstn-01] Allocchio, C., "Text string notation
494 for Dial Sequences and GSTN / E.164
495 addresses", draft-allocchio-gstn-01
496 (work in progress), November 2001.
498 [draft-wilde-sms-service-01] Wilde, E., "Registration of GSTN SMS
499 Service Qualifier", draft-wilde-sms-
500 service-01 (work in progress), January
501 2002.
503 Non-Normative References
505 [RFC2368] Hoffmann, P., Masinter, L. and J. Zawinski, "The
506 mailto URL scheme", RFC 2368, June 1998.
508 [RFC2629] Rose, M., "Writing I-Ds and RFCs using XML", RFC
509 2629, June 1999.
511 [RFC2806] Vaha-Sipila, A., "URLs for Telephone Calls", RFC
512 2806, April 2000.
514 [RFC2838] Zigmond, D. and M. Vickers, "Uniform Resource
515 Identifiers for Television Broadcasts", RFC
516 2838, May 2000.
518 [uri-clarification] World Wide Web Consortium, "URIs, URLs, and
519 URNs: Clarifications and Recommendations 1.0",
520 W3C uri-clarification , September 2001, .
523 Authors' Addresses
525 Erik Wilde
526 Swiss Federal Institute of Technology
527 ETH-Zentrum
528 8092 Zurich
529 Switzerland
531 Phone: +41-1-6325132
532 EMail: ietf@dret.net
533 URI: http://dret.net/netdret/
535 Antti Vaha-Sipila
536 Nokia
538 EMail: antti.vaha-sipila@nokia.com
540 Appendix A. Where to send Comments
542 Please send all comments about this document to Erik Wilde.
544 Appendix B. Acknowledgements
546 This document has been written using the IETF document DTD described
547 in RFC 2629 [RFC2629].
549 Thanks to Claudio Allocchio for his comments.
551 Full Copyright Statement
553 Copyright (C) The Internet Society (2002). All Rights Reserved.
555 This document and translations of it may be copied and furnished to
556 others, and derivative works that comment on or otherwise explain it
557 or assist in its implementation may be prepared, copied, published
558 and distributed, in whole or in part, without restriction of any
559 kind, provided that the above copyright notice and this paragraph are
560 included on all such copies and derivative works. However, this
561 document itself may not be modified in any way, such as by removing
562 the copyright notice or references to the Internet Society or other
563 Internet organizations, except as needed for the purpose of
564 developing Internet standards in which case the procedures for
565 copyrights defined in the Internet Standards process must be
566 followed, or as required to translate it into languages other than
567 English.
569 The limited permissions granted above are perpetual and will not be
570 revoked by the Internet Society or its successors or assigns.
572 This document and the information contained herein is provided on an
573 "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
574 TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
575 BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION
576 HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
577 MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
579 Acknowledgement
581 Funding for the RFC Editor function is currently provided by the
582 Internet Society.