INTERNET-DRAFT A. Vaha-Sipila
Expires 12-Jun-1999 Nokia
09-Dec-1998
URLs for GSM Short Message Service
<draft-antti-gsm-sms-url-03.txt>
Status of This Memo
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Abstract
This document specifies a URL (Uniform Resource Locator) scheme
"gsm-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 suitable
equipped computer or a phone.
Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . 1
1.1 What is GSM? . . . . . . . . . . . . . . . . . . . . . . . 2
1.2 Short Message Service . . . . . . . . . . . . . . . . . . 2
1.3 Short Messages and the Internet . . . . . . . . . . . . . 2
1.4 Formal Definitions . . . . . . . . . . . . . . . . . . . . 3
1.5 Requirements . . . . . . . . . . . . . . . . . . . . . . . 3
2. The "gsm-sms" URL Scheme . . . . . . . . . . . . . . . . . 3
2.1 Applicability . . . . . . . . . . . . . . . . . . . . . . 3
2.2 Formal Definition . . . . . . . . . . . . . . . . . . . . 4
2.3 Parsing a "gsm-sms" URL . . . . . . . . . . . . . . . . . 4
2.4 Examples of Use . . . . . . . . . . . . . . . . . . . . . 4
2.5 Using "gsm-sms" URLs in HTML Forms . . . . . . . . . . . . 4
3. References . . . . . . . . . . . . . . . . . . . . . . . . 5
4. Security Considerations . . . . . . . . . . . . . . . . . 6
5. Authors' Addresses . . . . . . . . . . . . . . . . . . . . 6
1. Introduction
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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. Because the user-agent must know whether it is
capable of sending the message or not, the used system must be
indicated somewhere in the URL. To keep everything simple, this
document specifies a unique scheme specifier for a Short Message
in the GSM system. Other systems MUST use other scheme specifiers.
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.
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
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URL. When a "gsm-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 "gsm-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 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
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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 = "gsm-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 "gsm-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 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
gsm-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.
gsm-sms:+3585551234567;via=+3585551000100
This indicates that the Short Message should be sent using the
SMSC at the given number.
2.5 Using "gsm-sms" URLs in HTML Forms
| When using a "gsm-sms" type URL as an action URL for HTML form
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| 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
[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)
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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 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 12th of June, 1999, or when a
new version is released.
A. Vaha-Sipila URLs for Short Messages December 1998