INTERNET-DRAFT A. Vaha-Sipila
Expires 24-Nov-1999 Nokia
19-May-1999
URLs for GSM Short Message Service
<draft-antti-gsm-sms-url-04.txt>
Status of This Memo
This document is an Internet-Draft and is in full conformance with
all provisions of Section 10 of RFC2026.
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Abstract
This document specifies a URL (Uniform Resource Locator) scheme "sms"
for specifying a recipient for an alphanumeric message (Short
Message) in a GSM-based mobile phone system. Short Messages are two-
way paging messages that can be sent from a suitably equipped
computer or a phone.
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Table of Contents
1. Introduction ................................................ 3
1.1 What is GSM? .............................................. 3
1.2 Short Message Service ...................................... 3
1.3 Short Messages and the Internet ............................ 3
1.4 Formal Definitions ......................................... 4
1.5 Requirements ............................................... 4
2. The "sms" URL Scheme ........................................ 4
2.1 Applicability .............................................. 4
2.2 Formal Definition .......................................... 5
2.3 Parsing a "sms" URL ........................................ 5
2.4 Examples of Use ............................................ 6
2.5 Using "sms" URLs in HTML Forms ............................. 6
3. References .................................................. 6
4. Security Considerations ..................................... 7
5. Authors' Addresses .......................................... 8
6. Full Copyright Statement .................................... 8
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1. Introduction
1.1 What is GSM?
GSM (Global System for Mobile Communications) is a digital mobile
phone standard which is used extensively in many parts of the world.
Named after its frequency band around 900 MHz, GSM-900 has provided
the basis for several other networks utilizing GSM technology. When
referring to "GSM" in this document, we mean any of these GSM-based
networks that operate a short message service.
1.2 Short Message Service
Short Messages [SMS] are two-way alphanumeric paging messages that
can be sent to and from GSM mobile phones. Short Messages can be
transmitted over the mobile phone's air interface using the
signalling channels so there is no delay for call setup. Short
Messages are stored by an entity called Short Message Service Centre
(SMSC) and sent to the recipient when the subscriber connects to the
network. The number of a cooperative SMSC must be known to the sender
when sending the message.
Short Messages can be mobile terminated (MT) or mobile originated
(MO). Mobile terminated messages are the ones that arrive to phones;
mobile originating messages are sent by a mobile subscriber. Networks
may support either, both or none of these.
A service similar to GSM SMS can be found also in other mobile phone
systems, but it may be called something else. The sender may not be
able to know whether it is capable of successfully sending a Short
Message to the recipient. The success depends on whether the network
operators have a suitable roaming agreement and a mechanism to
deliver the messages (theoretically it is possible to deliver short
messages between different network types, but this is not common at
the moment). It should be the network operator's responsibility to
inform the user about a success or a failure of the message delivery.
If there is a need to use the same scheme specifier for other network
types than GSM, this document should be updated.
1.3 Short Messages and the Internet
Short Messages can be used to transport almost any kind of data.
Some examples of possible uses for a Short Message are described
below.
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The Hypertext Markup Language (HTML) provides a way to collect
information from the user and pass it to a remote server for
processing. This functionality is known as "forms". A filled-in form
is usually sent to the destination using Hypertext Transfer Protocol
(HTTP) or mail. Short Messages can be used as the transport for these
forms. As the Short Message service is "out-of-band" as far as normal
HTTP-over-TCP/IP is concerned, this provides a way to fill in forms
offline and send the data without making a TCP connection to the
remote server, as the set-up time, cost and overhead for a TCP
connection are large compared to a Short Message. Also, depending on
the network configuration, the sender's telephone number may be
included in the Short Message, thus providing a weak form of
authentication.
Short Messages can also provide an alternative to a "mailto" type
URL. When a "sms" type URL is activated, the user agent MAY start a
program for sending an SMS message, just as "mailto" may open a mail
client.
The recipient need not to be a mobile phone. It can be a server that
can process Short Messages, either by gatewaying them to another
messaging system or by parsing them for supplementary services.
GSM Short Messages have a maximum length of 160 characters (from the
SMS character set), or 140 octets. However, Short Messages can be
concatenated to form longer messages. It is up to the user agent to
decide whether to limit the length of the message and how to indicate
this limit in its user interface, if necessary. There is one
exception to this, see section 2.5.
1.4 Formal Definitions
Definitions are written using Augmented BNF for Syntax Specifications
[RFC2234].
1.5 Requirements
Compliant software MUST follow this specification. Requirements are
indicated by capitalized words as specified in [RFC2119].
2. The "sms" URL Scheme
2.1 Applicability
This URL scheme is intended for sending a Short Message to a certain
recipient(s) through service centre(s). The functionality is quite
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similar to that of the "mailto" URL, which (as per [RFC2368]) can
also be used with a comma-separated list of email addresses.
In some situations, it may be necessary to guide the sender to send
the Short Message via a certain SMSC. For this purpose, this URL may
specify the number of the SMSC.
The notation for phone numbers is similar to that if [DRAFT-TELURL].
Refer to that document and to [RFC2303] for information on why this
particular format was chosen.
How the Short Message is sent to the SMSC is outside the scope of
this specification. Short Messages can be sent over the GSM air
interface or by using a modem and a suitable protocol (such as UCP
[UCP] or TDP [TDP]). Also, Short Message service options like
deferred delivery and delivery notification requests are not in the
scope of this document. Such services MAY be requested from the
network by the user agent if necessary.
Short Messages sent as a result of this URL MUST be sent as class 1
Short Messages, if the user agent is able to specify the message
class.
2.2 Formal Definition
The URL is case-insensitive. The URL syntax is formally described as
follows:
sms-url = scheme ":" scheme-specific-part
scheme = "sms"
scheme-specific-part = subscriber-id [";via=" message-centre-id]
["," scheme-specific-part]
subscriber-id = ["+"] phone-number
message-centre-id = ["+"] phone-number
phone-number = 1*phonedigit
phonedigit = digit / "-" / "."
digit = "0" / "1" / "2" / "3" / "4" / "5" /
"6" / "7" / "8" / "9"
2.3 Parsing a "sms" URL
1. <subscriber-id> is extracted. It is the phone number of the final
recipient and it MUST be written in international form with country
code, unless the number only works from inside a certain geographical
area or a network. Note that some numbers may work from several
networks but not from the whole world - these SHOULD be written in
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international form. All international numbers MUST begin with a "+"
character. Hyphens and dots are only to aid readability. They MUST
NOT have any other meaning.
2. <message-centre-id> is extracted if present. User-agent SHOULD try
to send the message first using this SMSC. If that fails, user-agent
MAY try another SMSC. The number of the SMSC is subject to the same
rules as the "subscriber-id" (see above).
3. If the URL consists of a comma-separated list of recipients, all
of them are processed in this manner. Exactly the same content SHOULD
be sent to all of the listed recipients.
2.4 Examples of Use
sms:+3585551234567
This indicates a mobile terminated (MT) Short Message capable
recipient at the given telephone number. The message is sent using
the user-agent's default SMSC.
sms:+3585551234567;via=+3585551000100
This indicates that the Short Message should be sent using the SMSC
at the given number.
2.5 Using "sms" URLs in HTML Forms
When using a "sms" type URL as an action URL for HTML form submission
[RFC1866], the form contents MUST be packaged in the Short Message
just as they are packaged when using a "mailto" URL [RFC2368], using
"application/x-www-form-urlencoded" MIME type [RFC1866]. The Short
Message MUST NOT contain any HTTP headers, only the form data. The
MIME type is implicit. It will not be transferred in the Short
Message.
The user agent SHOULD inform the user about the possible security
hazards involved when submitting the form.
If the form submission is longer than the maximum Short Message size,
the user agent MAY either concatenate Short Messages, if it is able
to do so, or it MAY refuse to send the message. The user agent MUST
NOT send out partial form submissions.
3. References
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[DRAFT-TELURL] URLs for Telephony. A. Vaha-Sipila. 1998. An
Internet-Draft (work in progress). <ftp://ftp.nordu.net/internet-
drafts/ draft-antti-telephony-url-05.txt>
[RFC1738] Uniform Resource Locators (URL). December 1994. T.
Berners-Lee et al. <ftp://ftp.nordu.net/rfc/rfc1738.txt>
[RFC1866] Hypertext Markup Language - 2.0. T. Berners-Lee et al.
November 1995. RFC 1866. <URL:ftp://ftp.nordu.net/rfc/rfc1866.txt>
[RFC2119] Key words for use in RFCs to Indicate Requirement Levels.
April 1997. S. Bradner. <ftp://ftp.nordu.net/rfc/rfc2119.txt>
[RFC2234] Augmented BNF for Syntax Specifications: ABNF. November
1997. D. Crocker et al. RFC 2234.
<URL:ftp://ftp.nordu.net/rfc/rfc2234.txt>
[RFC2303] Minimal PSTN Address Format in Internet Mail. March 1998.
C. Allocchio. RFC 2303. <URL:ftp://ftp.nordu.net/rfc/rfc2303.txt>
[RFC2368] The mailto URL Scheme. July 1998. P. Hoffman et al. RFC
2368. <URL:ftp://ftp.nordu.net/rfc/rfc2368.txt>
[UCP] Paging Systems; European Radio Message System (ERMES) (ETS 300
133-3). Part 3: Network Aspects. July 1992. European
Telecommunications Standards Institute.
[TDP] Telocator Data Paging Protocol (TDP). Version 2.0. July 27,
1995. Personal Communications Industry Association.
<http://www.mot.com/MIMS/MSPG/pcia_protocols/tdp_v2p0/index.html>
[SMS] Digital Cellular Telecommunications System (Phase 2+):
Technical Realization of the Short Message Service (SMS) Point-to-
Point (PP) (GSM 3.40). Version 5.2.0. May 1996. European
Telecommunications Standards Institute.
4. Security Considerations
It should be noted that the user agent SHOULD NOT send out Short
Messages without the knowledge of the user because of associated
risks, which include sending masses of Short Messages to a subscriber
without her consent and the costs involved in sending a Short
Message.
The user agent SHOULD have some mechanism that the user can use to
filter out unwanted destinations for Short Messages. The user agent
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SHOULD also have some means of restricting the number of Short
Messages sent.
5. Authors' Addresses
Contact person and version control responsibility for this
specification:
Nokia Mobile Phones
Antti Vaha-Sipila
P. O. Box 68
FIN-33721 Tampere
Finland
Electronic mail: antti.vaha-sipila@nmp.nokia.com
Please include your name and electronic mail address in all
communications. If you want to receive the newest version of this
specification electronically, send mail to the address above.
This document expires on the 24th of November, 1999, or when a new
version is released.
6. Full Copyright Statement
To be included in the final RFC submission.
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